# intermittant problem 85 gti cis-e running lean O2 sensor???



## 1985gticis (Mar 11, 2010)

still having intermittent problems with my 85 gti cis-e? Pretty sure its cis-e because of the DPR on the side of the airbox/fuel distributor. (not 100% positive so correct me if im wrong please) 

Symptoms 
generally every morning or after the car has completley cooled down for about 6+ hrs she runs "great" After a couple times of driving throughout the day or even the next time i go to drive it she runs lean struggles to stay running so i turned up the idle just under 2k. then when i take off from stop lights under load at 1-2k rpm the fuel mixture seems to just lean out and wants to die. So because of this i have to feather the gas and clutch on take offs
replacements 
I replaced both fuel pumps/filter a couple of months ago as the inline was bad, and plugs and wires, cap and rotor are good. also just yesterday i put a new CTS on and had no change in symptoms running lean. Then found a vacuum leak at the ISV fixed that as well as several small ones. cant find any more vacuum leaks. Still ran the same that same day. 
my thoughts
I think that the O2 sensor is "shorting out"/ not sending signal or correct signal when it is still warm. By disconnecting it will it make my car run more lean and only send 10ma to the DPR? Or could my air/fuel ratio be off? A/F concerns me because I bought the car from a kid and he said the guy before him had it "tuned" Or could it be the DPR switch itself? What else could be causing it to run lean intermitantly like this? 
Thanks for the help


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## ziddey (Apr 16, 2006)

*Re: intermittant problem 85 gti cis-e running lean O2 sensor??? (1985gticis)*

Sounds like you've done a lot of troubleshooting already. The next step is to measure the dpr current and see what the car is doing and go from there. Being able to see how the ecu is responding allows you to spray ether everywhere and watch the response. Have you verified the ignition timing is proper? Checked the accordion boot for tears? Got a vacuum gauge you can hook up? Have you tried unplugging the o2 sensor? Under warm conditions, the maximum the o2s can enrichen is to 20ma. With it unplugged when warm, yes, dpr will be pegged at 10ma.
Usually it's an underlying problem, instead of the mixture actually needing adjusting, but this far down the road, you might as well adjust it and see where it gets you, especially since it's been tampered with before.
I made a long dpr test harness so I can watch dpr current (as well as lambda voltage) from within the car while driving.


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## 1985gticis (Mar 11, 2010)

*Re: intermittant problem 85 gti cis-e running lean O2 sensor??? (ziddey)*

Go to leave today from school which it drove excellent on the way there and ran like crap couldn't even drive it! I looked around everything again and was going to disconnect the O2 sensor to see if that would change anything and it wasn't even plugged into anything! and couldnt find where to plug it into. and isn't the lower the ma reading mean richer and higher the number the leaner. now im starting to think that my DPR is bad or my ecu. Those are the only things that I can think of because it is such an intermittent problem and "only" acts up after the first drive of the day.


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## ziddey (Apr 16, 2006)

*Re: intermittant problem 85 gti cis-e running lean O2 sensor??? (1985gticis)*

ok, if the o2 sensor is unplugged, there's a starting place.
You should build a dpr test harness / cut the dpr wire to measure current. Nominal current through the dpr is 10ma. The proper tune will result in stoich at 10ma. DPR allows extra fuel. Under closed loop, if the ecu is reading rich from the o2 sensor, it will lower dpr current, thus provide less additional fine fueling to lean out the mixture and bring it back to stoich. If it receives lean from the o2 sensor, it will increase dpr current to provide additional fuel to bring it back to stoich.
Without the o2 sensor hooked up, the ecu will provide higher current through the dpr when cold, as normal (cold engine, richer mixture). But as the engine (cts) warms, the ecu will lower current through dpr, and if your mixture is set too lean (vacuum leaks), you will run lean when warmed up, especially with no o2 sensor to provide feedback.
Your car should have a heated o2 sensor, so you should find a two pin plug for the heater as well as a single green wire with brown plug for the o2 sensor signal wire.
As a crude way of setting up the mixture, you can try this: Warm up the car until it goes lean. Measure the voltage of the unplugged o2 sensor to ground. Dial the mixture and blip the throttle between adjustments until you're at about 0.8v. That should result in a driveable mixture, depending on how bad your vacuum leaks are.
Have you flexed your accordion boot yet?
This is all assuming your o2 sensor still works in some form.. If it was unplugged, perhaps it needs replacing.
So figure out your o2 sensor issue, and rig up a way to measure dpr current and go from there. That's the only way you're going to be able to truly see what's going on, and be able to decide if your dpr/ecu is working or not.


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## 1985gticis (Mar 11, 2010)

*Re: intermittant problem 85 gti cis-e running lean O2 sensor??? (ziddey)*

thanks for the help and ya no more vacuum leaks accordion boots are new
and also where does the O2 sensor plug into? I cant even find any loose wires near the O2 sensor to plug into. There are 2 separate wire lines that plug into wiring along the fire wall and go under the car, haven't followed all the way because its in a parking garage currently and don't have a jack or enough room to get under the car. also like i said before the car usually runs great for the first time of the day but not after that. how could the ecu/dpr have intermittent problems like this? and also is there a link to show how to make a dpr reader?
again thanks again for the help greatly appreciate it


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## Glegor (Mar 31, 2008)

*Re: intermittant problem 85 gti cis-e running lean O2 sensor??? (1985gticis)*

the wires for the o2 sensor are behind the intake manifold. kinda by where the a/c lines go into the cab. there are 2 connections. a round connector comin off a green wire, and a 2 wire square connector. it plugs into both of those.
also, check your ignition timing, mine was at 6* when i got the car, and it ran like crap, so i upped my timing to about 24* and now it runs great.


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## 1985gticis (Mar 11, 2010)

*Re: intermittant problem 85 gti cis-e running lean O2 sensor??? (Glegor)*

i dont thing the timing can cause an intermittent problem. 
Like i said before after sitting for about 6 hours the car runs good the entire time i drive it until i shut it off and drive it a second time it runs like ****. 
this is INTERMITTENT or untill the car gets fully warm.


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