# Need urgent DPR tuning help!



## URIN 2ND (Oct 29, 2001)

Hey guys,

First off, yes, I searched! Here's the deal.

Picked up an '89 1.8L 16V GTI. Idle was way off when I bought it; idled at ~2400 RPM and would instantly stall out if the TB linkage touched the idle switch. In that condition, it failed smog slightly off scale high on NO numbers. HC and CO were OK. Seemed like it was a little lean.

Brought it to my mechanic; he didn't look at the DPR numbers, but he adjusted the idle mixture screw, the idle screw on the TB, and the TB linkage. Within 60 secs, he had it idling at about ~1050 RPM, and the TB linkage was closed on the idle switch and it would stay running. I also installed a new O2 sensor. Then I went to get it smogged. This time, NO was very low, but HC and CO were WAY off the scale high (something like 3.2XX...about 400% too high). Clearly, it was all of a sudden too rich.

Today, I made a DPR test harness. I am sure the wires are correct. It doesn't hunt at idle - it stays at 19.5 mA constant. When I rev the engine then let go, the readout on the meter swings down to -6.0, and within ~1 second it's back up to a steady (non-hunting) 19.5 mA.

I can turn the mixture screw a full turn in any direction, and there's no change to the readout. The car will die before the readout changes (if leaning). The idle raises when enriching, but again, no change to the readout.

I only have a few days left on my temporary tags, so I need to get this thing sorted out ASAP! Does it sound like maybe the DPR is bad?

I should note, when the idle drops below ~1100 or so, it lopes VERY badly, almost like a race-cammed V8, close to dying. The idle also corrects itself; sometimes it will be at ~900, and it will randomly raise itself to ~1100 and smooth out a little. Not sure what this is all about.

Any suggestions? Please let me know if you can help. Thanks in advance!


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## normlhero (Aug 6, 2008)

*?*

Did you get this figured out?


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## ziddey (Apr 16, 2006)

sounds like the dpr is working fine. For some reason the ecu is causing the enrichment. Personally, I've found that with a warm CTS, the ecu will only enrichen to ~20ma, which is what you're seeing. If further enrichening via the screw causes the idle to elevate, then indeed it means that you're somehow still running lean, and the ecu is responding to lambda signal properly, albeit maxxing at 20ma (upper trim limit essentially).

So indeed if that is the case, when you lean the mixture, the car will lean out and die.

So if you richen the mixture, take the allen key out, and blip the throttle, you should start to see the dpr reading come down and start oscillating.

How is your ignition system? How about ignition timing?

If I'm reading correctly, you're able to close the idle switch at idle without the car stalling out now?

Are you able to pull the injectors and check spray pattern? Does spraying starter fluid around the injectors cause the idle to go up? Other vacuum leaks?

Good news is that your cat is still good, seemingly. From my experience, these cars should be able to get by HC/CO even with a terribly cat; it's NOx that's the difficult one.



So since your dpr is pegging ~20ma, it sounds like the CTS is warming up as it should. If you wanted to rule that out, you can get a resistor to simulate a hot condition (personally I've just shunted the wires, although that's advised against; I don't know the ecu circuitry to be able to say if it's really hard on it or not)

Knock sensor ok? Typically, these just fail deaf if I understand correctly, so that shouldn't be an issue either way.

CSV isn't stuck open, right?

It is strange that you're still seemingly running lean (maxxed dpr current, idle rises with enrichment), yet you've got low NOx and high CO/HC.

Again, what's the situation with your ignition system?


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## URIN 2ND (Oct 29, 2001)

ziddey said:


> sounds like the dpr is working fine. For some reason the ecu is causing the enrichment. Personally, I've found that with a warm CTS, the ecu will only enrichen to ~20ma, which is what you're seeing. If further enrichening via the screw causes the idle to elevate, then indeed it means that you're somehow still running lean, and the ecu is responding to lambda signal properly, albeit maxxing at 20ma (upper trim limit essentially).
> 
> So indeed if that is the case, when you lean the mixture, the car will lean out and die.
> 
> ...


It's still effed up. CTS and O2 sensor are 5 days old. Ignition system is in good shape, and the timing is set properly...though, with the RPMs moving up and down slightly with each adjustment to the DPR screw, I've had to re-set the ign. timing over and over again. Annoying!

I have a spare fuel dist/DPR, ECU, and ISV all pulled from an '89 GLI in the yard. Only thing is, one of my ECU's has a green label w/ part number 104/105, and the other one has a red label w/ a different part number. Though both were from 1989 16V's. Should I try swapping any of these into my car to see if the DPR readout gives some feedback?

Went to a smog station on recommendation of a friend...he's helping me get it passed. Basically the smog guy is just retarding the ignition timing a ton. He got the HC, CO, and the NO all within spec...almost. The NO on the 25mph run was over by **1 PPM**!!! So I had to come back the next day to try again (he's not charging me until it passes). Max was 71, I logged a 72. :banghead:

So today I went back...I think I had my exh. manifold nuts a little loose (long story) and forgot to snug them...this caused me to go back up to gross polluter status - HC and CO were WAY up because air was leaking pre-cat.

So I have to try again on Monday. Tags are now expired. 

What do you think I need to fix in order to get my DPR to give me a normal readout that I can use to make adjustments? ECU or DPR? I appreciate the smog guy helping me pass the car, but this "guess and check" method is taking forever. I'd love to actually be able to use the test harness to set the DPR. :banghead:



ziddey said:


> So if you richen the mixture, take the allen key out, and blip the throttle, you should start to see the dpr reading come down and start oscillating.


If I rev it, it drops to -6.0, then within 1 second it's back up to 19.5-19.6 mA. It doesn't oscillate. Any feedback on that?!

Thanks for the help guys, I appreciate it.


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## ziddey (Apr 16, 2006)

If you have an idle that hunts, that's a sign of a bad oxygen sensor or vacuum leaks. Improperly set idle screw will cause elevated idle, idle that falls to slowly, idle that drops too much and near stalls before recovery (if it recovers).

Since you have a new o2 sensor, is the connection ok?

Cis-e ecus are interchangeable. The only exception is the fox cis-e, which doesn't have provisions for wot enrichment, and doesn't use an isv.

You say you've cleaned out your ISV as well?

How are your grounds?


Ignition timing shouldn't be changing much at all despite idle fluctuations. How gross of fluctuations are we talking about here?

If you have a timing gun, you can try checking timing at idle, and at the rpms you're testing at for the 15mph and 25mph runs.

Again, HC/CO should be easy to get to pass with these cars


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## WaterWheels (Aug 14, 2005)

URIN 2ND said:


> Picked up an '89 1.8L 16V GTI. Idle was way off when I bought it; idled at ~2400 RPM and would instantly stall out if the TB linkage touched the idle switch.
> 
> It doesn't hunt at idle - it stays at 19.5 mA constant. When I rev the engine then let go, the readout on the meter swings down to -6.0, and within ~1 second it's back up to a steady (non-hunting) 19.5 mA. . . I can turn the mixture screw a full turn in any direction, and there's no change to the readout.
> 
> I should note, when the idle drops below ~1100 or so, it lopes VERY badly, almost like a race-cammed V8, close to dying.


First the mA reading, a steady non-fluxuating 19.5. That sounds like what is known as lean-stop. The system is detecting via the O2 sendor that the mixture is too lean and is trying to richen it. Book numbers say 20mA is the max at idle it will go, but 19.5 is close enough as no two systems or meters are exactly the same. So I would say the ECU is doing it's part in trying to correct the mixture, but is the data it is recieving correct, can't say.

The rest sound a lot like a camshaft phase problem. 16V engines use two camshafts that have to be set exactly against each other or the engine will never run correctly. You can force it to idle, like making the idle higher, but the mixture will never come into spec due to the cam to cam phasing being off. I hope you have a manual, with a 16v you really need one, and can check the camshaft timing. I would not do any tinkering before being 120% sure they are installed properly.


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## URIN 2ND (Oct 29, 2001)

Man, you guys are great. I wish the other forums on Vortex were still up to the level of this one. They used to be, in the good old days...but not so much any more! 

Let's see...cam phasing. When I bought the car, I had suspected that it had a cam/cams and that possibly the phasing was off. I've since installed Autotech cams, but I can't recall if when I was checking the DPR, it was before or after I'd swapped cams. Turns out it had a Euro intake cam, and it didn't have the same inner gear as the stock cams (stock ones have the 'o' marks, this one had a '|' which did NOT line up at all with the 'o' on the exhaust cam. We made 1000% sure the cams are phased correctly since installing the Autotech's...in fact, it idled and ran slightly better once we put the AST cams in.

O2 sensor...I'm certain the connection is good. Used the posi-lock twist connectors supplied with the Bosch O2 sensor and those are impossible to screw up. Actually, I'd bought 2 brand new O2 sensors and suspected the Walker one I bought a week prior was bad (I was trying to save 5 bucks), and then bought the Bosch a week later. 



> If you have an idle that hunts, that's a sign of a bad oxygen sensor or vacuum leaks. Improperly set idle screw will cause elevated idle, idle that falls to slowly, idle that drops too much and near stalls before recovery (if it recovers).


Idle screw o-ring is brand new. Idle doesn't hunt, per se...it would stay pretty solid for several seconds, then bump itself up and stay solid a couple hundred RPM's higher. I have not messed with it recently; this is before I put the new cams and new O2 in. But it seemed like the ISV was trying to keep it from stalling out; the idle was very lumpy at ~850 and once in a while it actually would drop and die. I don't think it does this anymore, since swapping the cams.

Vac leaks...early on when trying to fix this, when I swung by my mechanic to try to get the car to idle at all, he sprayed starter fluid on all vac lines and there were no changes in the idle. We didn't do the injectors though. I did buy new O-rings and bushings for the injectors last week, but I have not put them in yet. I'll try this on Sunday.

The ISV does hum when the key is in position 2, but I'm not sure how to check it any further. I've got the other one I can swap in, but again, I'm unsure of its condition.

So...what do you think I should do at this point? I haven't looked at it in a couple weeks because I wasn't sure what else to do and I didn't want to make it worse. I feel a little rejuvenated and ready to look at it again. :thumbup:


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