# Drop in power, decrease in MPG. (continued)



## 465995a (Aug 24, 2009)

k-
So I had a long post discussing this issue, but it got too long to make sense to most it seems. So here is the story in short:
in a 1998 Jetta GL 2L 8v (156k on the clock)
was getting 30 mpg regularly, with mixed driving, then the cat melted down, clogged, and was driven partially clogged for a few days before it was fixed, and new O2 sensors were installed. After that, the car has only gotten 27 mpg at its best on the highway, and an average of 24 mpg. 
It feels sluggish, and its 0-60 time is around 14-15 seconds... .(i know its the 2.slow, but that time should be closer to 10 as stock). 
I have checked the MAF, even replaced it, mad no difference. 
It has new wires, plugs, cap and rotor. 
The plugs are not fouled. Replaced all the vacuum hoses. 
Changed air filter, and oil. 
Pulled intake to check for leaks, and checked the injectors, all spray fine and uniform. 
Flow rate is good, no fuel leaking. 
Compression has been checked, 210 psi per cylinder.
only thing i am left to think is that somehow the ECU is bad?
Any ideas? I know my way around the engine bay, and this one has got me stumped


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## MecE2.0 (Dec 20, 2005)

*Re: Drop in power, decrease in MPG. (465995a)*

if the ecu was bad you wouldn't be driving at all. just going to throw this out there, as its usually the case, but your cat burnt out and it doesn't just happen on its own. a meltdown generally means you were either running pig rich or were misfiring on a regular basis for some time. there's nothing to suggest that it was running that rich (especially since the usual suspects have been eliminated). since the plugs/wires/cap/rotor were good that really only leaves 1 other culprit -> your coil.


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## 465995a (Aug 24, 2009)

^ i will see if i can pick one up, swap it, and see if there is a change.
it does feel like it is "missing" a little at idle, from time to time. I have pulled the coil and inspected it, as recommended in the other thread, it looked fine, also made sure it had a good ground.


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## MecE2.0 (Dec 20, 2005)

*Re: (465995a)*

ya, and as has been mentioned before, even if you can just test it out with a used one thats known to work, only for a couple days of course, then you can eliminate a possibility. i wouldn't recommend sticking with a used one, but thats up to you.
so give that a try. if you've noticed it then its probably happening, and has been happening for sometime (long enough to melt your cat core). btw, visual/watermist inspection really only works when trying to find a crack. these things can fail without cracking.


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## 465995a (Aug 24, 2009)

^ could the knock sensor cause the same issues?


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## vendettajetta (Mar 7, 2008)

isn't 210 psi per cyl. high! Checked mine and average about 175 per cylinder.


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## MecE2.0 (Dec 20, 2005)

*Re: (vendettajetta)*


_Quote, originally posted by *465995a* »_^ could the knock sensor cause the same issues?

doubtful. i mean i suppose if it came loose from the block and began to pick up false knocks it would retard (and give the performance drop) but odds are it just wouldn't be picking them up and you'd probably notice some pinging.

_Quote, originally posted by *vendettajetta* »_isn't 210 psi per cyl. high! Checked mine and average about 175 per cylinder.

the gauge cylinder pressure on a given cylinder isn't really a big indicator of anything until its compared with the others. if all of them are around 210 then its fine, probably just has a lot of carbon build up. if 3 were 210 and one was 150 i'd be concerned.


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## Jay-Bee (Sep 22, 2007)

*FV-QR*


_Quote, originally posted by *vendettajetta* »_isn't 210 psi per cyl. high! Checked mine and average about 175 per cylinder.



I had 190-195psi across the board on my AEG.


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## 465995a (Aug 24, 2009)

*Re: (MecE2.0)*


_Quote, originally posted by *MecE2.0* »_ya, and as has been mentioned before, even if you can just test it out with a used one thats known to work, only for a couple days of course, then you can eliminate a possibility. i wouldn't recommend sticking with a used one, but thats up to you.
so give that a try. if you've noticed it then its probably happening, and has been happening for sometime (long enough to melt your cat core). btw, visual/watermist inspection really only works when trying to find a crack. these things can fail without cracking.

so i just swapped it out with a new one, ran a few 0-60, and seemed to make no difference. is that grounds of ruling it out? or do i need to run it for a while and actually check the mpg? I would think if it was bad, there would be a difference in performance (ie. 0-60). Also, it still seems to miss every so often while idling, like once every few seconds.


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## MecE2.0 (Dec 20, 2005)

*Re: (465995a)*

if its still missing bad then its not the source (or at least the only source) of the misfire problem. still, run it for a couple days and see what happens, give the ecu time to get used to it. so no CEL? no flashes even? usually if there's a problem thats causing heavy misfiring the CEL will start to go nuts. have you had you codes checked at all yet to see if its been storing something?


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## 465995a (Aug 24, 2009)

*Re: (MecE2.0)*


_Quote, originally posted by *MecE2.0* »_if its still missing bad then its not the source (or at least the only source) of the misfire problem. still, run it for a couple days and see what happens, give the ecu time to get used to it. so no CEL? no flashes even? usually if there's a problem thats causing heavy misfiring the CEL will start to go nuts. have you had you codes checked at all yet to see if its been storing something?

yes, i have checked the codes many times, no CEL, no soft codes, all the "readiness" checks are good, meaning it has fully cycled, with no codes.
it hasnt been misfiring, it accelerates smooth, it just feels more gutless than before, at idle when i say "miss" i mean like it skips a fire every few seconds.
I will check the plug wires resistance again, but like i said, they are relatively new, as well as the plugs.
The only CEL i have gotten recently was when i pulled the intake and tested the injectors, i put it all back together, and it just cranked a few times without starting, i beleive it was because the fuel pump relay was not plugged back in all the way. But even after it started, it ran really rough for a few seconds, threw a bunch of codes, and then smoothed out, ran just like before the teardown after that, reset the codes and nothing since, (that was a couple weeks ago), other than crappy MPG


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## MecE2.0 (Dec 20, 2005)

*Re: (465995a)*

hmmm. kind of a stumper. let it run a couple days and see what happens. the only other possibility that comes to mind is that your FPR is shot and you're dumping a little extra fuel around idle. it can have a pretty dramatic effect on idle quality and fuel econ around town, plus affect performance. with mine the idle was horrible and made my 270 cam seem much lopier than it ought to.


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## 465995a (Aug 24, 2009)

*Re: (MecE2.0)*

FPR is fine, i checked it as one of the first suspects, while i checked fuel flow on the return line, measured a consistant 2L/min of fuel, and 36~45psi pressure, using a vacuum pump, on/off for the high/low pressures.


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## MecE2.0 (Dec 20, 2005)

*Re: (465995a)*

huh, and everything else checks out eh? well i'm stumped, short of a caliper/drum thats binding, or a blockage further down in the exhaust system.


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## 465995a (Aug 24, 2009)

what are the odds of the timing belt skipping a cog on the intermediate shaft.... i would think that the odds are pretty low, but i hear the "thermo tensioners" are know to be faulty.


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## MecE2.0 (Dec 20, 2005)

*Re: (465995a)*

its possible, but you'd be throwing a CPS code (as with most timing issues). just for ****sngigs you could check and redo you're timing, you never know.


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## 465995a (Aug 24, 2009)

yeah, i just checked the timing again, it is set exactly at 12 deg BTDC.


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## MecE2.0 (Dec 20, 2005)

*Re: (465995a)*

what brand was the new cat? wonder if that could have been faulty.


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## 465995a (Aug 24, 2009)

^ i thought that too, had the pressure checked, by pulling the o2 sensors out, and checking differential, flow was fine.
as far as brand, im not sure, but it looks OE and it cost about 200 bucks. There is no efficiency codes, so im sure it is working fine, and i know that it does not control fuel mixture or anything either, it is merely there for emissions.


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## MecE2.0 (Dec 20, 2005)

*Re: (465995a)*

any luck getting this figured out? this has me pretty puzzled.


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## 465995a (Aug 24, 2009)

^ i just ordered a "vag-com" scanner, so we will see what it tells me. It just seems odd that everything is checking out fine and i am still having an issue.
maybe I'll replace the o2 sensor again.... Ive tested it with a scope, and it cycles back and forth smoothly between .2 and .9v, goes to 0 when the engine is decellerating, and fuel is cut off, pegs at 1 when the throttle is floored.
Am i wrong in assuming that an o2 sensor either works or doesnt work? I dont think an o2 sensor can go out of "calibration"


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## 465995a (Aug 24, 2009)

ok, so i have a basic vag com interface now. I was able to find a malfunction code for the rear o2 sensor, said "intermittant issue with the heater circuit"
I doubt this would have anything to do with the fuel economy, since this sensor is just measuring cat efficiency, not metering the fuel/air mix to the engine.

Also, what things should i view on the scope, and what is considered normal? Im guessing it will be something with the "lambda" it appeared that the timing was ok (21-12deg btc) and cfm measurements seemed ok.
What should the "lambda" readings say?


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## 465995a (Aug 24, 2009)

*Re: (465995a)*

update*
Here is what i was able to find with vag com.
















so it appears there is something wrong with the evap-emissions system.... MAF tests fine (as per vag-com's fuel trim info), and o2 sensors are fine, as per diagnostics.
What should i check/test that would cause no fault codes, and also keep the readiness from passing?
mpg has dropped to 22 now with the colder weather, so it would be nice to get this fixed!
Thanks again for the help!


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## cwcabrio (Dec 16, 2009)

*Re: Drop in power, decrease in MPG. (465995a)*

Sounds to me like you have a bad ECU relay. It causes an unstable voltage supply to your ECU making it mad... making your mix very rich therefore busting your cat, and the low mpgs.
Since you got the vag com, check the voltage suplly to your ECU to be shure.
Good luck, keep us posted.


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## MecE2.0 (Dec 20, 2005)

*Re: Drop in power, decrease in MPG. (cwcabrio)*

^could be. check the ground continuity, switched power and the hot terminal. its worth a try, although, when i wired in the '87 the power relay went and it just wouldn't run.


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## 465995a (Aug 24, 2009)

bad ecu relay? thought the ECU had constant power.... I have checked all battery connections, and replaced all vehicle grounds, did that when checking the maf. 

anything else? just seems weird that I have no CEL, but the evap system has not passed yet


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## MecE2.0 (Dec 20, 2005)

*Re: (465995a)*

well it has a constant like a stereo does. just enough to hold the memory. the relay pulls a signal and sends the proper voltage for running (so hence when the relay went for the '87 it wouldn't start at all). this is really puzzling dude. wish i could have a peek at this thing in person, hard to do this online.


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## cwcabrio (Dec 16, 2009)

*Re: (465995a)*

The ECU relay is the third from left to right, and on the second row of relays from the fuse row up. May be with a big 30 number on it. Worth to check is simple.
Tell us what you find out.


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## 465995a (Aug 24, 2009)

*Re: (cwcabrio)*


_Quote, originally posted by *cwcabrio* »_The ECU relay is the third from left to right, and on the second row of relays from the fuse row up. May be with a big 30 number on it. Worth to check is simple.
Tell us what you find out.

there is no relay in the 3rd spot, but there is in the 4th, or 3rd from the right, on the 87 terminal (output) it measures the same voltage as at the battery, 12.2v (key on, engine off), 14.4v (key on, engine on) and 0v with key and engine off..
and here is the latest vag reading... looks like everything has passed now, but the fuel economy is still low 20's.... not good!


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## cwcabrio (Dec 16, 2009)

*Re: (465995a)*

Weird, no relay??? .... could you post a pic of your fuse/relay box, your spark plugs and the reading on the Measuring Blocks (08), Group 000 of your VAG COM with the key on and engine not running???
I suspect of the ECU relay because a 97 GTI had it bad, and didn't bring any faults with the VAG COM. Changed it and ran smoths as silk.


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## 465995a (Aug 24, 2009)

*Re: (cwcabrio)*


_Quote, originally posted by *cwcabrio* »_Weird, no relay??? .... could you post a pic of your fuse/relay box, your spark plugs and the reading on the Measuring Blocks (08), Group 000 of your VAG COM with the key on and engine not running???
I suspect of the ECU relay because a 97 GTI had it bad, and didn't bring any faults with the VAG COM. Changed it and ran smoths as silk.

i dont have a full version of vag com, just some 3rd party device, so group 000 is not available. I did see on group 2 or 3 that the ecu voltage was good, no difference.
here is a picture of one spark plug, the others all look the same, and i have changed them twice since this problem occured, and each time they look the same.
















Here is a picture of my fuse/relay box. #3 is empty, however, the 87 and 30 terminal of the spot show voltage with the key on.








Thanks again for all of your help!


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## 465995a (Aug 24, 2009)

also, if the pcv valve was not working right, wouldnt it throw a code?


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## 465995a (Aug 24, 2009)

bumpo?


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## cwcabrio (Dec 16, 2009)

*Re: (465995a)*

Sorry about the ECU relay check... the '97 GTI was OBD 1 (Guatemala market)... so my bad.
So let's start over... if you will... melted cat due to rich mixture... replaced cat and O2 sensors... what caused the inyection to run rich?
Almost all sensors checked and or replaced....
Have you checked the purge valve of the gas tank vapors?
If not clossing correctly, it could let the gas vapors to be suck by the intake, making the mix rich.
Have U checked wiring and connections of sensors like MAF and O2?
Have U checked the sensor on the TB?
May be a leak in the exhaust system?
Good luck. Keep posting.


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## 465995a (Aug 24, 2009)

exhaust is all new from techtonics. Sensors, and wiring all test and look good, maf tested a little over 85 GPH at redline and full throttle, which is good according to ross-tech.
TB tests fine as well, with smooth operation from open to close.
I would think that an o2 sensor would either work or it wouldnt... so i will assume they are fine since they are recently new.
I have not checked the purge valve, im assuming you are talking of the valve that is in line with the carbon canister, behind the air box? I would guess that if i unplug the wiring, it should hold a vaccum. or should it be open?


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## cwcabrio (Dec 16, 2009)

*Re: (465995a)*

Yeah, thats the one. And I guess so to, it should be closed if unplugged.


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## buttman226 (Jul 23, 2009)

*Re: Drop in power, decrease in MPG. (465995a)*

Man your car is weird. The EVAP system runs from the passenger side wheel fender to back to the gas tank. That doesn't reduce MPG though. Run a dirty air filter, I actually got better MPG because the car gets less air, lol.
Also if you are running all this new exhaust, hate to break it to you, that reduces MPG. 
Here is my story. ABA 97 OBD2. Stock, goes to LA and gets like 38 MPG.
P Flow addition + 2.5 inch exhaust and ABD big bore intake, oooh down to 30 MPG.


_Modified by buttman226 at 9:42 PM 1-3-2010_


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## Pry (Nov 27, 2004)

*Re: Drop in power, decrease in MPG. (buttman226)*


_Quote, originally posted by *buttman226* »_
Also if you are running all this new exhaust, hate to break it to you, that reduces MPG. 


I think a good mandrel bent cat-back would improve your MPG.


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## buttman226 (Jul 23, 2009)

*Re: Drop in power, decrease in MPG. (Pry)*

reduced mine, very noticable on long distances and upper RPM's. Of course, my 2.5 inch exhuast is somewhat excessive for the 2.0 slow, they run 2.5 on the 1.8t, stock is 2.25 for that one. 2.0 slow must be 2.0 or smaller.


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## 465995a (Aug 24, 2009)

Its just the 2.25 inch exhaust, and i have had the same setup from TT on other vw's mk3 and mk2 and it either stayed the same MPG or increased. 

so i just went on another long trip over new years, and the roads were horrible, had to drive 35-50 mph most the way for about 200 miles, ended up getting about 29 mpg. On the way back i was able to go 80mph, and the milage appears to be a little lower, i havent checked other than i know i only got about 160 miles at the half tank mark, i will see the exact amount when i go to fill up.


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## buttman226 (Jul 23, 2009)

*Re: (465995a)*

in the city, on my mk3 I get 160 for a half tank, and typically 350 total tank running a little into the reserve light. I'd check the MAF and air intake, throttle body. Recalibrate the throttlebody with vagcom.


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## cwcabrio (Dec 16, 2009)

*Re: (465995a)*

Just wondering, does your engine has EGR or Secondary air injection systems?
Thinking that if o2 working correctly, it may be getting extra air in the exhaust some how.
Good to hear mpgs coming up again.
Good luck. Keep posting.


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## 465995a (Aug 24, 2009)

^no EGR or secondary air injection on this car, so it rules that out.

it has been running rough on cold mornings, it never did in years past, it seems to miss quite a bit until it warms up for a minute.
which should rule out the o2 sensor, as they do nothing until the system goes into closed loop.


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## cwcabrio (Dec 16, 2009)

*Re: (465995a)*

Right, I guess only the CTS, AIT and MAF work in the mix for a cold start.
Have you checked the color on your spark plugs lately to see if rich mixture present? First pics seem pretty good to me, just a little dirt around the seat.


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## 465995a (Aug 24, 2009)

^ oh, im sure it is running a little rich, if it was lean, i dont think it would effect the economy as much.

I will have to check out the readings a little closer on the VAG tool for the CTS and AIT...
any other suggestions? Im about ready to unload a few rounds into it!


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## akid420 (Apr 23, 2009)

i read most of the posts but not all so this might have been asked already. do u have same exhaust on that the cat melted on? my cat melted a while back and all the peices went into my resonator. didnt know till after i replaced the cat and decided to update exhaust. when i cut the resonator off a few hundred chucks of what looks like bees nest feel out.


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## yay0 (Oct 2, 2008)

*Re: (akid420)*

Okay if you have a vag-com why dont you watch the sensor data and drive? Also check fuel trims(long term and short term). Anything + is the reason for your increased consumption


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## 465995a (Aug 24, 2009)

so when its cold it starts up just fine, runs really smooth for about 5 seconds, then i starts to miss every second or so. Also, while accelerating it does the same, but is intermittent.


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## 465995a (Aug 24, 2009)

Also, in group 6 on the vag-com readings it shows 1.2 G/s for the maf, and 60% load, the MAF reading does not change, and the Load barely does. Yet in other groups, the MAF and Load read just fine, and change with engine speed.
My only concern is that at 60 mph the engine is showing under 60% load. I would think that at that low speed it should be a bit below 50%
also, at idle it shows 15-20% load, at a stand still.
Im assuming the load calculation must be some basic formula taking vacuum and rpm into account, am I wrong?


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## 465995a (Aug 24, 2009)

the intake and coolant tempurature readings also appeared normal from cold to regular operating temp.


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## famousken (Aug 26, 2009)

*Re: (vendettajetta)*


_Quote, originally posted by *vendettajetta* »_isn't 210 psi per cyl. high! Checked mine and average about 175 per cylinder.

Mine checked out at 150psi, so I think so


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## 465995a (Aug 24, 2009)

^ its probably due to carbon build up. 190 psi is normal on a new aba engine


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## 465995a (Aug 24, 2009)

so i decided to ditch the cat, pick up a PEM chip fome BFI so i can just run single 02 sensor and through in a 268 cam from TT.
Figure if im gonna be getting decreased mpg, might as well get some power out of it


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## tdogg74 (Mar 1, 2002)

*FV-QR*


_Quote, originally posted by *465995a* »_so i decided to ditch the cat, pick up a PEM chip fome BFI so i can just run single 02 sensor and through in a 268 cam from TT.



....aaaand you'll get a CEL. The rear sensor has to be in the stream or it will throw a code. Also, cant unplug the sensor at the harness.


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## 465995a (Aug 24, 2009)

*Re: FV-QR (tdogg74)*


_Quote, originally posted by *tdogg74* »_
....aaaand you'll get a CEL. The rear sensor has to be in the stream or it will throw a code. Also, cant unplug the sensor at the harness. 

according to the PEM description on BFI, the PEM software does not use the SAI, or 2nd o2 sensor.


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## 465995a (Aug 24, 2009)

is that wrong? does it still need the 2nd o2 sensor with the PEM software?


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## tdogg74 (Mar 1, 2002)

*FV-QR*

Yep. The second you either take the rear sensor out of the exhaust OR unplug it, you get a CEL. 
This has happened on both PEMs I own.


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## 465995a (Aug 24, 2009)

^ so i'll just remove it and hang it in the engine bay.
Is the 268 gonna be fine, or should i have gone with the 260?


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## tdogg74 (Mar 1, 2002)

*FV-QR*

And you throw a cel.


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## 465995a (Aug 24, 2009)

^ ok, but how is the drivability with the cams? should I just chip it and leave the engine stock? do I absolutely need a adj cam sprocket?


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## tdogg74 (Mar 1, 2002)

*FV-QR*

I ran the stage-1 PEM with a 276* cam with no issues. Idle was around 850 warmed up. Lope was....decent...I guess. (Im used to it) The stage-2 will bump the idle up to 1050 warmed up. Basically, if you run a stock cam, get the S1, any other cam, get the S2. Idle can be manually set with VAGCOM to whatever you want, but the 1050 idle will smooth out the 268* idle lope. 
You dont _need_ an adjustable cam gear unless you shave your head and need correct cam timing. Other-wise, it will move your peak torque around.


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## mannythechamp (Oct 21, 2009)

*Re: FV-QR (tdogg74)*

this problem has been entriguing me forever now!!! and keep us informed on that new cam thinking on a cam swap my self good luck bro ....


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## billmongold (Feb 20, 2008)

ive got a tt 272 cam and no cel on stock tune. got it c2 flashed then bam. cel.


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## 465995a (Aug 24, 2009)

268* cam went in last night, idle is ok, seems almost like it did before, except missing a lot more. I know that is just the "lope", and the PEM chip comes in today, and should fix that problem.
Anyone know of any "patches" for the shareware version of vag com?


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## tdogg74 (Mar 1, 2002)

*FV-QR*

"Patches" for what specifically?


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## independent77 (May 23, 2003)

*Re: (465995a)*

Patches.=hack=cheat.
Yep. my shareware ebay/vagcom is fully registered now. I'm not telling how.


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## tdogg74 (Mar 1, 2002)

*FV-QR*

only useful hacks with the PEM is idle speed manipulation. Everything else you would want to **** with has already been dealt with with the software.


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## 465995a (Aug 24, 2009)

*Re: (independent77)*


_Quote, originally posted by *independent77* »_Patches.=hack=cheat.
Yep. my shareware ebay/vagcom is fully registered now. I'm not telling how.

thanks d-hole.


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## 1lowGnster (Feb 18, 2010)

have you tried reseting your TB sensor?


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## 465995a (Aug 24, 2009)

^ how so?


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## 465995a (Aug 24, 2009)

so i just put in new chip. Idled like crap, had to floor it to get it started, figured it needed to "learn" the car, so i ran it around, til it warmed up, now it seems fine, but still seems like it is missing more than it should especially with an idle at around 1100 rpm.


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## tdogg74 (Mar 1, 2002)

*FV-QR*

Is your timing tight? Got a CEL?


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## badufay (Mar 17, 2006)

*Re: FV-QR (tdogg74)*

Plug in the Vag-com and post your readings from measuring group 018 and 025 please. 
Got some ideas that may help depending on your readings here.
-Ben


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## 465995a (Aug 24, 2009)

*Re: FV-QR (tdogg74)*


_Quote, originally posted by *tdogg74* »_Is your timing tight? Got a CEL?

everything is the same as it was with the stock chip. All i did was swap the chip. No CEL, I will run it again and see if it has starting issues again.


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## 465995a (Aug 24, 2009)

*Re: FV-QR (badufay)*


_Quote, originally posted by *badufay* »_Plug in the Vag-com and post your readings from measuring group 018 and 025 please. 
Got some ideas that may help depending on your readings here.
-Ben

here it is








And another issue, 








Im gonna call BFI tomorrow, seems there is an issue with the chip, which would explain the rough idle.


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## 465995a (Aug 24, 2009)

^ those readings (18, 25) were done shortly after cold startup. I didnt want to run it long with the error code, I also reset the code, and it immediately came back on (no CEL, only on vag)


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## badufay (Mar 17, 2006)

*Re: (465995a)*

Block 3 in field 018 is the cam shaft position phase deviationerror. it needs to read 0.0. loosen your distributor and rotate it until the block reads 0.0. what was your CEL for again?
-Ben


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## 465995a (Aug 24, 2009)

*Re: (badufay)*


_Quote, originally posted by *badufay* »_Block 3 in field 018 is the cam shaft position phase deviationerror. it needs to read 0.0. loosen your distributor and rotate it until the block reads 0.0. what was your CEL for again?
-Ben

so with the stock chip back in, group 18 looks a little different.








But either way, there is no "ROM" code now, so i will be sending the chip back to BFI and wait for a replacement.








even with the stock chip, revved to 1200 or so, it seems to miss every couple seconds, any thoughts? New plugs just put in.


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## tdogg74 (Mar 1, 2002)

*FV-QR*

What do you mean by "miss"? Miss on idle or miss when revving?


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## 465995a (Aug 24, 2009)

^ well, before the cam and stuff, it would seem to miss a little at idle, rev it and it sounded fine.
with the cam, i was expecting it to idle a little rough, but would think it would smooth out at higher rpms, So holding the idle with the stock chip at around 1200-1400 rpm, it seemed smooth but then would "miss" and drop a little in speed every so often, about 2-4 seconds between.
seems almost like a spark issue, but ive already been down that road.


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## tdogg74 (Mar 1, 2002)

*FV-QR*

Stock wires? How old are they? 
Stock wires suck. The connector part breaks if you look at them the wrong way. Over time they crack and deteriorate. If you pull them to change the plugs, they just die. You end up arcing to the head right at the plug/connector.


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## Jay-Bee (Sep 22, 2007)

*FV-QR*


_Quote, originally posted by *465995a* »_
And another issue, 










I have this code from my Unitronic flash, engine will operate properly but the checksum in the chip is not correct.
I have been dealing with an idle stumble or miss for a while now too. I throw no codes, wires and plugs are in good shape... 
My car is down right now due to the crappy crank position sensor failing on me, i'm wondering if this was a symptom a long time before it actually died on me, I have checked for vacuum leaks and everything, car runs fine except for a slight stumbled of about 50 rpms only at idle.
Will be replacing the crank sensor later this week, we'll see if it does anything with the idle stumble.
I'm thinking it might be due to my exhaust leak, but didn't think it would cause that.


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## 465995a (Aug 24, 2009)

*Re: FV-QR (tdogg74)*


_Quote, originally posted by *tdogg74* »_Stock wires? How old are they? 
Stock wires suck. The connector part breaks if you look at them the wrong way. Over time they crack and deteriorate. If you pull them to change the plugs, they just die. You end up arcing to the head right at the plug/connector.

no, they are about a year old. still look new. Same with cap and rotor.


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## 465995a (Aug 24, 2009)

*Re: FV-QR (Jay-Bee)*


_Quote, originally posted by *Jay-Bee* »_
I have this code from my Unitronic flash, engine will operate properly but the checksum in the chip is not correct.
I have been dealing with an idle stumble or miss for a while now too. I throw no codes, wires and plugs are in good shape... 
My car is down right now due to the crappy crank position sensor failing on me, i'm wondering if this was a symptom a long time before it actually died on me, I have checked for vacuum leaks and everything, car runs fine except for a slight stumbled of about 50 rpms only at idle.
Will be replacing the crank sensor later this week, we'll see if it does anything with the idle stumble.
I'm thinking it might be due to my exhaust leak, but didn't think it would cause that.


yeah, keep me posted as to how that goes, and if it fixes your issue. http://****************.com/smile/emthup.gif 

And I forgot to mention, Why does it show the engine under 29% load at idle?
How does it calculate "load" ? is it based on vacuum? is 25-30% normal at idle? I have replaced all vacuum hoses and checked for leaks.


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## tacurong (Jul 13, 2009)

*Re: (465995a)*

check your cam timeing your spark plugs look ok


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## 465995a (Aug 24, 2009)

well, I ordered a new breather hose, as the last one was cracked at the block outlet. Put it in, and decided to replace the PCV grommet, well, those things are very stiff, and very brittle. I ended up breaking it while removing it.
BUT, upon inspection, it seemed very dirty, and may be the "cat culprit" as it looked very oily, and could have been dumping the excess oil into the intake.
So I should have a new one in by thursday, then a few days to see if this was the issue the whole time.


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## badufay (Mar 17, 2006)

*Re: (465995a)*

You need to rotate your Dizzy until block 3 in group 018 goes from -12 to 0.0. you are on the very edge of it getting ready to through a cam shaft position error. also, did you say you replaced your actual PCV valve yet?
-Ben


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## 465995a (Aug 24, 2009)

^ no, i just broke it two days ago, so a new one wont be here until probably thursday or so. Im kinda glad I did break it, upon internal inpection, the seals were shot, and I highly doubt "spraying it out" would have done anything, probably made it worse.
So you say block 3 in group 18 has to do with ignition timing? Set it to zero at warm idle?


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## badufay (Mar 17, 2006)

*Re: (465995a)*

the pcv valve is a horrible design, they get clogged fairly easy on these cars, best thing to do is either run a catch can setup (been researching that a lot lately) or buy a bunch of extra grommets and clean the valve a lot more frequently....probably about every oil change or so. send me your email address and ill send you a copy of the procedure for setting the dizzy to 0.
-Ben


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## 465995a (Aug 24, 2009)

^ pm sent.


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## 465995a (Aug 24, 2009)

ok, so i just replaced the PVC valve, let the car warm up, and checked group 18 with vag com.
It now reads a flat zero, and I never touched the dizzy. I even drove it around a bit, shut it off, and turned it back on, still at zero.


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## badufay (Mar 17, 2006)

*Re: (465995a)*

If that value in block 3 of 018 is changing without you physically moving the dizzy, one of 2 things is happening; first either the dizzy itself is bad either internal wear of some other type of issue (or loose, make sure it is tightened down), or your timing belt is slipping off the intermediate shaft in the front of the motor..... If you can get your hands on a good working used dizzy, i would swap them out and see. It is looking more like a ignition/timing issue, let me scan the procedure for checking your timing at idle and high rpm to see if things are working correctly. check your email soon.... also can you post a snap shot of your readings from block 010 at idle (800-880 rpm) and also at 2500 rpm (2480-2520rpm) set up to read 001, 010 and 025, then do another snap shot of at idle only for blocks 001, 003, 018
-Ben



_Modified by badufay at 10:53 AM 3-12-2010_


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## 465995a (Aug 24, 2009)

*Re: (badufay)*


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## 465995a (Aug 24, 2009)

^ timing looks to spec, but the 2nd column of 010 looks like it may be off, i believe it corresponds to engine load.
I have already checked for vacuum leaks, and replaced all old suspect hoses, Also, at idle, it measures about 18 mmHg vacuum.


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## 465995a (Aug 24, 2009)

*Re: (465995a)*

so i let it warm up completely, and the second column in group 010 seemed to get worse.
















also, (in block 2 of 010) it jumped up to 10 when i floored it, and dropped as low as .4 when i let off the throttle in gear.


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## badufay (Mar 17, 2006)

*Re: (465995a)*

dont worry about block 2 in 010. what does look pretty crewy is your TB angle. at idle, that thing should be reading more around 3° +/-. the lambda also isn't the greatest, how old is your front o2 sensor. have you cleaned your TB lately and reset the basic settings?


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## 465995a (Aug 24, 2009)

^ the front o2 sensor is less than two years old. How do you reset the TB basic settings?
also, what column pertains to what o2 sensor? (ie. which one is front and which one is back?)


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## badufay (Mar 17, 2006)

*Re: (465995a)*

disregard, about the o2 sensors, they look good. the one that keeps jumping around field 1 in 025 is your front o2 sensor, 02 is your fuel trim at cruise, and 03 is your fuel trim at idle. your TB needs to be cleaned real good, then reset with vag-com.....basic settings, 098, and wait 30 seconds. here read this about the tb.....
http://faculty.ccp.edu/faculty...x.htm
-Ben


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## 465995a (Aug 24, 2009)

^ so if i dont have the full version of vag-com, unplugging the battery for a while will also reset it?


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## badufay (Mar 17, 2006)

*Re: (465995a)*

i guess you can, big thing is cleaning it though


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## 465995a (Aug 24, 2009)

^ so i cleaned it out (it wasnt very dirty at all) and now at idle it is about 4.5-5 deg. at idle.
With the key on, engine off, it reads 6 degrees. (this was after the reset)


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## 465995a (Aug 24, 2009)

good news, just drove the car on a trip a few hundred miles, and it got 31 mpg. so we will see if it stays that way.

ALso, i took apart the old PCV valve and it was definitely not functioning correctly, the rubber diaphragm inside was completely brittle and stiff, it crumbled when i pushed on it.
So, my guess is that the bad PCV valve let an excess of oil/fumes into the intake, and it went through and clogged the cat, causing a meltdown.
We'll see if anything else changes when I get the BFI stage 1 chip put in this next weekend.


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## 465995a (Aug 24, 2009)

yup, 32mpg, with recent fillup, The BFI chip however, not so good, installed the second one they sent me and the car would not even start, put the old stock one back in, and it ran just fine.
now i get to wait another couple weeks for a new one to arrive.


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