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Post by ShrimpBrime on Mar 29, 2020 11:55:33 GMT -5
OK fellas 2002 VW Jetta, has a 2.slow liter motor. Really simple and easy to work on.
Story -
Had an issue a few weeks ago with my cam sensor. The motor was derated 50% and would only rev 3000 rpm.
So...... I replaced the cam sensor. Ran fine up till last night.
Issue:
Started the car and it was good at cold high idle. I was adjusting my stereo when the idle came down to about 700 rpm and the engine started surging. Perhaps pulsing??
If I gently raise the RPMs the surging goes away.
Pulled codes. Has some evap and oxygen sensor codes that have been there since I purchased the vehicle last year. I can clear these codes, but the engine light stays on or comes back immediately and likely due to the Evap system which is fine and generally doesn't effect drive-ability. Same with the oxygen sensor.
If any of you Car gurus have any tips tricks and pointers, let me have them.
I have not done a diag beyond pulling codes. Cam sensor throws no errors. If it was the crankshaft sensor the car won't start. (which I haven't tried to start it today) Figure to ask you guys before getting dirty today.
Help??
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Post by ShrimpBrime on Mar 29, 2020 12:09:49 GMT -5
OK researching.
Check throttle actuator (mechanical malfunction)
Check for vacuum leaks. (Ah yes, good thought there)
The only 2 logical leads I have so far.
Seems to high idle and rev fine, surges at idle in gear as well.
Will accelerate just fine. However I didn't leave the driveway, I took a separate vehicle.
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Post by ShrimpBrime on Mar 29, 2020 15:24:44 GMT -5
OK went outside for a diag. Started the car, no issue.
Only difference is it was raining last night but dry today.,
I suspect ignition coil or wire issue.
Further diag next time the issue occurs.
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Post by dr4g00n on Mar 29, 2020 15:40:05 GMT -5
Sounds to me like a vacuum leak or something to do with the tps/maf. Could also be that faulty O2 sensor(s).
Edit: Wrote this before your last post. Could've very well been a bad/wet connection somewhere.
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Post by Mr.Scott on Mar 29, 2020 18:09:59 GMT -5
All computer related.
Could be something wet or corroded, but leaning to just needing a re-program most likely.
Never came fully out of limp mode.
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Post by ShrimpBrime on Mar 29, 2020 18:33:45 GMT -5
All computer related. Could be something wet or corroded, but leaning to just needing a re-program most likely. Never came fully out of limp mode. Oh it wasn't "limp" mode. That's OBD 1 american. This was pure 50% de-rate. Just like your tractors with After-treatment. But I think your right about electrical. This I can believe. Never seen a car act like that before lol. No ryme or reason to it. Today, cured!! lol |
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Post by Bones on Mar 29, 2020 18:40:07 GMT -5
Yeah, something being affected by the moisture/water present at that time. I'd suggest just looking things over and coating anything suspicious with some dielectric, should stop it at least for now.
If it's near a hot component, I can't say what to use but dielectric probrably woudn't work there. Maybe if it's a case of a wire going to a sensor in the exhaust manifold/exhaust period, shrink tubing?
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Post by ShrimpBrime on Mar 29, 2020 19:38:25 GMT -5
OK so what would be the sensor/s that would cause this kind of issue if unplugged? TPS MAP/MAF ? Probably those possibly crankshaft sensor. Not too many. No idea where the ECM is. I'll look that up shortly.
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Post by zila1 on Mar 29, 2020 19:41:41 GMT -5
Grab a spray bottle and spray around the wires/ignition while it's idling and see if can get her to act up. Looks at it in the dark and see if you see any arcing under there. Corroded or broken grounds. Loose or corroded battery connections. Have you checked fuel pressure. Low or uneven fuel pressure will drive those suckers crazy and surge.
Edit: Can you pull codes on it? Does it have a coolant temp sensor code showing?
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Post by ShrimpBrime on Mar 29, 2020 19:50:49 GMT -5
Yep pulled codes. 0Xygen sensor bank one #2 heated circuit blah blah. Inspected it, started backing out of the threads, wires are good. Sensor is vibrated to death. Not cheap. I will bargain with E-bay like I did with the Cam sensor lol. (19$ for a cam sensor.... and it works! lol) happy day for me there! Rotors are 52$ a piece if 11". No idea, I haven't pulled on off yet. I don't have cash for that right now. Wife and Kid both filed for no employment and well... Illinois isn't fast about anything so.... Yea. Just on me again. Fun times. Started looking for work already. No one is hiring at this time .
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Post by Bones on Mar 29, 2020 20:14:07 GMT -5
That just sux but at least you know what's probrably causing it.
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Post by zila1 on Mar 29, 2020 20:15:41 GMT -5
Ever tried cleaning an o2 sensor in gasoline? They get soaked overnight in a closed container, shake em around a bit. Lightly scrub them with a soft brush soaked in gas. Let it dry overnight and give it a try again. I've never tried it. I've only heard guys talk about it. I always thought o2 sensors were one of those components that couldn't be cleaned but you never know.
Edit: Jon, that car doesn't have a TPS on it right? Electric Throttle Body?
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Post by Mr.Scott on Mar 30, 2020 17:55:38 GMT -5
Should be drive by wire, yes.
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Post by ShrimpBrime on Mar 30, 2020 18:33:12 GMT -5
Yea it's fly by wire, but still has mechanical throttle plate. (servo) I had read these will open and close slightly and cause surging, but most I read about where while driving.
Car was fine to and from work today. Can't diagnose nothing now. I did even stop and restart the car when it happened. It still had the issue, so I figured to take a different vehicle so I didn't have to deal with a possible break down. Unfortunately, I had somewhere to go and it was kinda rainy so never took the time to look at it while the symptoms occured.
I know, it's not much to go by, but that's all that happened. lol.
edit: I did not look at it at the shop. Just wanted to go home. You know how that is....
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