HELP - Can oil buildup in the intake/MAF/air cleaner cause rich running when cold?

[95jettaguy]

I've got a 1995 Jetta GL, 2.0, 5-speed, 140,000km that runs rich/bucks for about a minute when first started up. The problem clears up once the car has had a chance to warm up, only to return after it sits long enough to cool down. I recently cleaned the MAF, hoping that this would fix the problem, but it did not. When I had the MAF off I noticed that a fair amount of oil had accumulated in the air filter, MAF, and intake tube. I’m thinking that this is probably the result of a dirty or bad PCV valve, which I’m hoping to change soon. Does anyone know if the oil buildup or a bad PCV valve could be causing the engine to run rich at startup? I’m baffled by this one, so any other ideas are appreciated too. Thanks.

[stuzman]

Originally Posted by 95jettaguy

I've got a 1995 Jetta GL, 2.0, 5-speed, 140,000km that runs rich/bucks for about a minute when first started up. The problem clears up once the car has had a chance to warm up, only to return after it sits long enough to cool down. I recently cleaned the MAF, hoping that this would fix the problem, but it did not. When I had the MAF off I noticed that a fair amount of oil had accumulated in the air filter, MAF, and intake tube. I’m thinking that this is probably the result of a dirty or bad PCV valve, which I’m hoping to change soon. Does anyone know if the oil buildup or a bad PCV valve could be causing the engine to run rich at startup? I’m baffled by this one, so any other ideas are appreciated too. Thanks.

I'm not sure if it will run rich, but I do know that when oil or its vapor gets on the MAF sensor, the engine will rev up to about 3K RPM's and then immediately shutdown. I've had to clean the sensor twice for this condition. Since, this sensor measures the amount of airflow coming into the engine, it stands to reason that you could have a rich mixture if the incoming air is incorrect as measured by the MAF.

[95jettaguy]

Originally Posted by stuzman

I'm not sure if it will run rich, but I do know that when oil or its vapor gets on the MAF sensor, the engine will rev up to about 3K RPM's and then immediately shutdown. I've had to clean the sensor twice for this condition. Since, this sensor measures the amount of airflow coming into the engine, it stands to reason that you could have a rich mixture if the incoming air is incorrect as measured by the MAF.

Thanks for the feedback. I recently cleaned the MAF, as well as the air intake boot and it's associated tubes. There was a lot of oil and gunk in the boot and around the PCV valve, so I think that I sill try replacing it sometime soon. I'm thinking that I will also clean the throttle body & fuel injectors as well, though this might not get done until the weather warms up. If anyone has any other suggestions they are appreciated.

[irbf]

I have this same exact problem on my 95 Jetta. In fact, just cleaned the entire intake yesterday and replaced the PCV. The valve was $55 from the VW dealer and the rubber grommet ($5) that holds it to the valve cover must also be replaced as you will destroy it removing the old valve. Not sure if this will solve the excess oil in the intake issue. It started smoother this AM and I could tell a difference in the idle...still have a mystery bucking problem shortly after start though (see different thread)...


Are there not any VW engineers that read these posts??? How about some help from Auburn Hills????

[itzed]

Oil from the PCV is a common problem with these cars. But I doubt it's causing your cold drivability problems. The bucking sounds like an electric issue. It's also common that these cars eat plug wires for some reason. If it's been more than 40K since they were changed, I'd try a good old fashioned tune up with new plugs, wires, cap, and rotor.

[zeek1403]

How do you get to the MAF and how do you clean it?

[itzed]

Originally Posted by zeek1403

How do you get to the MAF and how do you clean it?

Remove the air cleaner assembly and disconnect all the the intake plumbing that connects it to the throttle body. The MAF meter is built into the air cleaner assembly, being the first thing you the air gets to right after it passes through the air filter. It looks like this:

http://www.germanautoparts.com/Volks...Jetta/Fuel/5/1

Spray the thin metal element of the MAF very gently with throttle body cleaner or carb cleaner. It's located behind a screen but it's very delicate so you need to be careful not to damage it when spraying too hard or too close. Just let the element dry naturally by air - don't touch it. While it's all disassembled, spray all the hoses and clean them out too, chances are you'll find lots of oil. Spray the throttle plate butterfly too. Let it all dry by air and then put it back together. If you still have a high idle problem it's probably the PCV valve that needs replacing, which is common.

[saunders80]

jus wondering if you ever solved this problem? i have been having the same problem with my 95 gl III... i believe it to be the temp sender (sensor) but havin't tried replacing it yet, any responds would be appreicated