I have 1995 Jetta GL. It's a 2.0/5 speed with 136,000km. It's starts up great and revs nicely the first time that I press the gas pedal (stopped in neutral). After the first rev up it's very choppy and rough when I continue to rev it. If I try to drive it like this it feels horrible and stumbles. It usually smells pretty gassy when in this state, so I'm assuming that the mixture is running a bit rich, but I'm not sure. If I stay parked and rev it for about a minute or two things clear up and it drives fine. It's worse when it's cold, but happens in all temperatures. My mechanic has tried to figure it out twice. The first time he replaced the coolant sensor. The second time he checked for air leaks, but didn't find any and said that was all he could do without getting into replacing different parts to see if any fix it. The parts he suggested he might try were the MAF or the ECU, both not cheap. Does anyone have other suggestions before I head down this (potentially expensive) diagnostic road. Many thanks.

I just barely had that same problem. At first i changed my fuel pump, helped the reving, but it still didn't go away. Turns out, i shorted out my MAF sensor which shorted out a piece of my ECU, $300 bucks for parts and labor. But now my car runs great. Also you might want to put in a full tank of gas of premium, then throw in some Fuel Injector cleaner you buy at Autozone. Cleans up nicely!

I agree with the MAF diagnosis. I saw a thread about cleaning it in alcohol. I've never tried this, but it sounds right. The fuel injector cleaner also sounds like good advise. I like sea foam. Most auto parts places carry it. I use it every 7500 to 10000 miles. I don't have stock in the company, really. It is the only thing short of taking things apart that I've found that works well enough to not be a waste of money. I'll have to remember to check and see what consumer reports says. It sounds like something is sticking, you may also clean up any other parts of your injection that is readily accessible. The air filter may need replacing, but it doesn't seem all that likely from what you said. I would try shutting the car off after it has warmed up then seeing if you have the same problem after re-starting it. Basically, try to rule out temperature. Depending on where you live, try starting it in a warm location such as a properly vented garage to see if cold air is making something stick.

How do I run seafoam through my 96 Jetta?