I have a 97 A4 2.8 WITH 105,000 mi. The car randomly will not start or in the first few minutes of driving after coming to a stop will die when I press the gas (usually in the middle of the intersection). After turning and holding the key many times I can usually get it started but when it does it runs very rough with alot of black smoke and I have to keep it at high rpms for a minute or so until it runs smoothly. The first time this happened I had it towed to my mechanic and the diagnostic showed no codes or faults and I was told there was nothing that could be done because they could not find anything wrong. Since then it has been to the dealership 5 times and they have repalced the o2 sensor and a spark plug wire but cannot find anything specific and it seems to start every time they have it. I am sooo frustrated! Has anyone experienced this problem? HELP!!!

 

Probably the coolant temp sensor is reading to cold. Replace it. Its just below the intake air hose between the air box & thottle body. 4Wires.

 

Yup I agree 100%... The engine coolant temp. sensor... Thats the first thing I thought of after reading the first 2 sentences in your post... Cheap easy DIY fix too. Check out www.ecstuning.com for the part. They have it pretty cheap, but its gunna be pretty cheap anywhere you go. i doubt local places like autozone or napa or advance auto parts will have it in stock (but they wont charge you shipping if they have to order it). The dealer will probably be the most expensive but they are pretty much guaranteed to have it at all times. Too much info? Sorry.

It is odd though that you dont have any fault codes stored.

 

Thanks for your response! Is this sensor something that would cause a fault and will it get worse if left alone?

 

It should cause a fault.. It could get worse. If the ects hasnt been replaced yet, it would be worth a try since its like a $10 part and easy to replace yourself. It could also be a bad MAF, but youd deffinately get a code for that, i think.... Try replacing the engine coolant temp sensor and go from there.

 

MAF (mass airflow sensor)? If that is correct the dealership cleaned it when they replaced the o2 sensor, still no faults but that was thier best guess.

 

ya maf=mass air flow sensor... Replace the ects and let us know what happens.

 

It doesn't necessarily cause a fault.

 

Thanks so much! I replaced the ECT and have not had any more problems.