Nevin

I just got a 1999 Audi A4 Quattro in a trade. The maf sensor is bad but it would still run and drive ok. Then all of a sudden it wouldn't start. I charged the battery up and it started and ran for a little and shut off again. After awhile of cranking it finally started again and I tried a few more times and it was fine. Shut it off and waited a few minutes then the same problem. Could this just be from the maf sensor? Also I found a plug not in. I was told it was the coolant temp sensor. Where it goes is blocked off by a bolt and washer. Why is it like that and should I put the sensor back in? Also it is about 15 degrees right now if that would effect anything.

clancy

It is important the coolant temp sensor be functional. Especially in restarting a warm engine. Not many true repair pros still monitoring this forum because of the age of the cars. But all the info you need was posted previously if you spend time with the search function.

John535is

Do you know the MAF sensor is bad or is it the MAF?
Do you have or can you get a code scan done, preferable a vag scan (VCDS or similar).

If you pull the MAF to clean it out, when you reinstall and connect the wiring, turn the ignition on but not start. You should hear the MAF go through a series of full open, full close cycles for about 20 seconds while it realigns itself. If it doesn't you need to do an adaptation which you need a VCDS or similar device to activate the adaptation program. The later models do it automatically, but some of the earlier ones don't.

Nevin

Thanks for the replies! I did a search of the forum and couldn't find what I was looking for. I thought the maf was bad because when it was plugged it the car would idol rough. I just replaced the maf and it didn't seem to fix the issue. The car runs fine with the maf unplugged. Do I have to do something special after replacing it? Like clear the code? I did turn the key and not start it for 20 seconds

clancy

I believe that if the MAF is unplugged the car runs on a fail safe type program that assumes rather than knows the amount of air passing to the intake. I believe this program runs the car a bit rich. IF this is correct AND your car has an air leak such as a cracked/broken air supply hose AFTER the MAF then possibly the fuel rich supply along with the air rich supply because of an air leak is why your car runs smoother with the MAF unplugged??? Look for aged and cracked or broken air supply hoses.

Becoming adept at searching this forum for answers is frustrating. When I first started posting questions here I was told to STFA or search the forum archives. I did without much success. I was sure someone would answer my questions. But sometimes they didn't do so as quickly as I needed the answers. So I kept searching and leaned how to do better searches. I also learned I had to read a lot of long threads that were barely related until I finally found the answers were indeed here. So, the answers are here, you just need to continue to refine your search technique. Or, pay a shop to repair your car.

People who know what your problem is and how to solve it are not going to continue to repeat the info they have given previously. They eventually get tired of saying the same thing over and over to new posters. Do it yourself also means research it yourself...