# 2.0 aba obd1 idle stutter cold start rough idle car dieing at stops issues



## InSaneV (Oct 24, 2009)

Hi gang, wanted to just post up my saga of tracking down a issue I recantly had with a cold start rough Idle issue on my transplanted 2.0 aba obd1 into a mk1. Like many other people that have had this issue I came to the fourms to see what others have done to fix this problem. Well seems there are alot of reasons for this type of issue so I wrote my list down and headed to the garage. 

Alittle pre info on the car and engine: 84 Jetta coupe ( german made and imported ) I must have a german man to thank for that some where. 2.0 aba transplant winter of 2011, replaced plugs, dist. cap, rotor and wires after a spray down test showed arcing. Did timing belt and idler pulley and ensured timing was correct. 

:beer:*IF YOU NEED MORE BEER TIME MY FIX IS AT THE BOTTOM*​:beer: 


Here is the laundry list of things I had tried to see if it would remedy my problem with the rough idle on start up and the irradict idle droping ( sometimes dieing at stops ). 

*Vac test*: replaced some suspect hoses, ensured all non used plugs or ports where capped. No results, least I know its not a vac leak. 

*Clean throttle body:* removed intake line and gave TB a good cleaning ( wasnt that dirty to start with ) but wanted to be sure anyways. No results still had both issues. 

*Clean MAF:* as above removed MAF cleaned it properly with MAF cleaner and decided to clean out the intake while I had it apart as well. both where fairy clean still but dosent hurt to do it while its out. Still no results having same issues. 

*Clean ISV:* seen it mentioned in alot of cases of irradict idle so thought hell might as try it if anything it will be clean. Still no results but got lots of clean parts  

*Check IAT and CTS SENSORS:* checked and swapped both just in case...no change. 

*TPS SENSOR:* checked and swapped with another on I had both didnt fix either issue. 

So at this point I was scratching my head and pondering if I had cleaned them up properly or if what I thought was working isn't and more importantly was my :beer: in the fridge cold yet. After a quick :beer: fridge trip and a look down of my list of things to try I tried swaping out other cleaned MAF's and ISV's I had around all with the same results. Well that was enough for one day after work so I packed it in for the night to try again after the next day. 


*MK1 JETTA 1 - BEER FRIDGE 3 - OWNER 0*​ 

Next day after searching for more results I came across that the crank position sensor could be the root of all this cold start idle misery I was having. Could this be the holy grail to my issues I thought, its got to be whats acting up. 

*CRANK POS. SENSOR:* Commonly reffered to as the RPM sensor as well iirc. Well sold myself on the thought that this was going to be the fix for my issues and id be daily driving my jetta again. What.....really......oh man. ( only thing I had bought so far )....No results  

Now I was really :banghead: what could it be, I had visit my ol' friend the :beer: fridge and ponder what is causing my issues. well after a few :beer:ski's I decide the next day I would go to the wrecker and grab a few items like another ecu, coil and a obd2 port I could wire in to my ecu ( as I left the L and K lines in the harness just in case ) and try swaping out those items to see if they are somehow bad. 

*JETTA 2 - BEER FRIDGE 6 - OWNER 0*​ 
Day 3 and the Jetta is starting to kick my ass..... :beer: fridge is an acceptable loss those guys should be in division 1. Off to the wreckers at lunch time got in and out under a hr with most of the parts I was looking for...first time I went in to grab anyuthing so I was impressed how many good parts where around. Got home and went right to the garage.....well ok right after the :beer: fridge. 

*ECU REPLACED:* Wow got lucky and found one at the wreckers with the same digits and everything.....still no change in car behaviour 

*COIL:* Now this is a hard part to find....well one that isnt cracked anyways...wonder how many cars came here cause the coil was cracked. So empty handed there I did the spray down test again on it....nope still good no arching visual or sound and more importanlty car did not die or react to it being sprayed down. 

Well now im really freaking  I have tried pretty much everything people have posted on the vortex and im still at the point of no driving the Jetta.....off to the :beer: fridge. After staring at the car for a hr and talking to a neighbour throwing ideas around, It was decided to check the plugs, wires and such to make sure they where still good or what have you. That and the timming might be suspect as well so ill recheck that after another :beer: Well that didnt happen.....neighbour liked the :beer: as much as I did that night. 

*JETTA 3 - BEER FRIDGE 14 - OWNER 0 BUT WITH A SLIGHT BUZZ*​ 
Well not ready to addmit defeat yet I went to the garage after work again looking at the plugs, wires, cap and rotor as well as the timming of the engine. Oh thats right if your still awake and reading this I didn't hit the :beer: fridge yet.......yet. 

*SPARK:* all seemed good plugs where in a condition I would think they be at with the car running in limp mode im sure. Cap no cracks or scaring and the rotor looked good as well. Wires where soildly on the plugs and no signs of damage. replaced all ran the car and did a spray test to be sure again. Didnt solve my issues but no Issues where added either. 

*TIMMING* Set up the car to TDC and both the crank and the cam marks where pretty bang on but the distributer was a hair off so ajusted the distributor by losing the bolt that holds it down and twisting it to meet dead on to the rotor at TDC tightend down and brought out the gun. Timming was very close could be tweaked alittle more but for the most part ran good ( after it warmed up that is ) 

Well at this point I was heading for the :beer: fridge and :banghead: on the door....... what could it freaking be, I caught myself almost saying I wished I had my CIS back.......wow that was freaking close! After talking to some of the guys at work who are not mechanics per say but all very machaniclly inclined guys said I should check the fuel filter and pump as it seems like I wasnt getting any gas. So Finally Friday night and I can spend alot more time than a hr or two trying to solve my problem. 

*JETTA 4 - BEER FRIDGE 15 - OWNER 0*​ 
*FUELING:* Started the car to listen to the fuel pump of the car....primes like it should with the turn of the key to on. Starts and hums like it should while running, put the volt meter to it and have 12v so relay and pump are seeing the needed voltage. Unhook pump from tank, this is where you wish you had 4 arms and attached the psi tester to the back of the pump where you just removed the fuel line from the tank. Had the wife crank the car ( she had a evil grin on her face ) and saw the pump was pulling the required psi to move the gas to the front of the car. Checked the fuel filter had a bit of tank grit in it ( let the tank get to empty in case i had to pull the fuel pump ) but nothing crazy as to plug it up and the gas was still clear. Changed the fuel filter anyways just in case. No change in car issues. 

Well after cleaning up and yes drinking a cool fresh :beer: I was almost ready to throw in the towel and have a vw tech look at it. I figured I would wire in the obd2 port and get a autoparts store scan it for me to test if the port worked and what if anything the cars ecu was saying. So taking apart the knee knockers of the dash so I could run my wires to where I wanted them I thought ahh what the hell ill check the fuse box see it any fues are blow or relays are lose. Nope no fuses are blown but hey that relay made a funny sound when I flicked it with my finger ( thats my high tech way of checking relays internals ). Hum its the heated O2 sensor relay.....it didnt even cross my mind that this could cause or even effect my car with the issues it was having. Having a spare I decide to take it apart to see what went on in it....im curious  cracked the top off and thing looked brand new no corrosion or burnt smell.....but hey look there is spring laying on the relay that looks like it should attach to another part of the relay. Still not even thinking this could cause my issue I repaired the spring reattached it and put the cover back on. At this time my neighbour came over to see how i was making out and bringing :beer: over to refill the fridge. So not thinking about it ( and who can with :beer: out ) I just put the relay back in and started discussing what I had done since our last meeting of like minded :beer: drinkers. 

Well after talking about it for a bit he's like crank it over and lets hear it again maybe we can use our :beer: powers to make it run. I was like meh ok but man I have tried everything I can think of.....crank it over and bam.....Idles like a champ off the get go.....NO I said that not what was causing my my issues...can't be.......yup it was. 

*HEATED O2 RELAY:* So im still not wrapping my head around this but my guess is that the little spring that popped off the little plate and the contact inside the relay was confusing the ecu with mixed signals and was throwing it into limp mode and such but with mild braking the plate would engage or something while the car was in limp mode and giving the ecu fits. 

Went and drove the car around the neighbour hood starting stoping accelerating hard cornering sitting in traffic with a nice steady 800 rpm....omg its like a new car again. 

Hope this helps others in the future or currently with these type of issues and if I where to do it all over again I would check the fuse box first :beer: 

*FINAL SCORE: JETTA 4 - BEER FRIDGE 24 - OWNER 1* 
*most of beer consumed after test drive of fixed vehical - test course was not available sorry - try this at home - and dont drink and drive*​


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## InSaneV (Oct 24, 2009)

3 weeks now and still running great no issues......bring on the cam and new lifters


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## anjaloveshervw (Jan 27, 2008)

Such a funny post, thanks for taking the time to share this story


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## cameronj1019 (Aug 6, 2012)

Really an 02 relay causing all of those problems????? Amazing... I hope this fixes my 2.0l. Starting to get angry trying to figure out the problem


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## pisuicas (Oct 4, 2011)

i have similar problems, but i cannot find the heated o2 sensor on my aba. which number has on the back?


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