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Discussion Starter · #1 ·
On the commute home today, my 1.8t tiptronic with 60,000 miles started 'bucking'. The check engine light never came on. I was in stop and go traffic on the freeway. I immediately turned off the air cond to reduce the load as much as possible. It continued to do this more often than every minute or two. It never died, but when it was doing it I couldn't accelerate; the car would coast down. I had a chance to go 40+ mph, and opportunity to raise the rpm to 2,000+, but it did the same thing. When I stopped and had it in park, it would idle, then the rpm would go up a bit and light black smoke would come out, then the idle would drop below normal for a couple seconds. Then it would idle regular for 20 seconds and do it again.
On the phone the dealer thought bad gas since no codes were ever shown. Amoco says they test there gas every day and haven't had any water in it. They also said the delivery had last been a couple days ago.
I did put a full does of Amsoil PI (injector cleaner) in with the fill. I do this every few months. Could it cause vapor lock?
What other issues may be the culprit and how would I test for them? Thanks for your ideas.
 

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Re: (ganseg)

Really need a VAG COM to look for misfire codes. Find out which cylinder is misfiring, then swap coil packs with a good firing cylinder. If misfire "moves" with the moved (bad) coil pack, get a new one. If misfire stays on the same cylinder, it's more than likely the ICM.
I'd hope the dealer would return the old MAF sensor to you (request it); after all, you're paying for a new one.
(ouch)
Clean the old MAF with 95% isopropyl alcohol. Rubbing alcohol is only 70% purity and contains glycerin-which is bad for the sensor.
 

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Discussion Starter · #5 ·
Re: (Electron Man)

To clean it with the iso. alchohol, do I just poor it thru or does the MAF come apart?
I appreciate the archived article. My display group 32 values were -2.3% and +11.7. The 11.7 is outside of the authors recommended range of +/-10%. Thanks!
 

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Re: (ganseg)

...could also be a (large) air leak on the intake side. Suspect all rubber connections to the valve body.
 

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Discussion Starter · #7 ·
Re: (Electron Man)

The codes only came after about 80 miles with the problem. They were several random misfire codes and a couple of misfire on cylinder 4. Then the diagnostic readout said too high reading on MAF and display group 32 values were -2.3% and +11.7. The 11.7 is outside of the authors recommended range of +/-10%.
Could this all have been a dirty MAF? It is currently running fine, but only 10 miles so far. I checked the resistance between the middle prong of the ICM and the four outer prongs and all measured 2600 ohms - just like the one that was taken off. Just asking for future reference. Thanks!
 

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Re: Car 'bucking' like when a person doesn't know how to use a clutch... (ganseg)

Quote, originally posted by ganseg »

On the phone the dealer thought bad gas since no codes were ever shown. Amoco says they test there gas every day and haven't had any water in it. They also said the delivery had last been a couple days ago.

I suppose they have a bridge for sale, too?
I don't believe them for a minute.
I would definitely fill up with gas from a different gas station ASAP.
 

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Discussion Starter · #9 ·
Re: Car 'bucking' like when a person doesn't know how to use a clutch... (chrishart1)

I just changed the fuel filter and caught some of it in a glass jar. I let it set a day or two and now water separated out. So I think it is ok. And since I had a full tank, I am still using it with no problems. (VW wanted $100 to siphon it out.)
Any advice on how to clean the old MAF I have? Thanks.
 
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