'02 A6 4.2 I've owned it since 09/05

Got in the car the other day and it wouldn't start. Starter would just wind away sounding normal, but with out the vroom of the engine starting, similar to being out of gas I guess.

Tow'd it to my mechanic, 1 mile from work >:-( and next day he says it started no problem for him in the morning. They looked up and down, inside and out, and found nothing wrong.

He suspected there may be something wrong with some temp sensor, thinking it's COLD outside and dumping mass amounts of fuel in, flooding it. He said if it happens again, push the gas pedal ALL the way to the floor which will stop the injectors, and allow more O2 in burning off the extra fuel.

It's happened two more times now in the last week and a half, and each time I was able to get it running by pushing the gas pedal all the way down like he said...

Anyone seen this before? Suggestions?

My CEL is on, but only thing in the computer is O2 sensor failing... and he said that would not be causing this.

Thanks,
Dave

 

It could be a vacuum leak. I have had this happen a couple of times as well. I believe the culprit was the broken vac lines. There were several little ones that were wore out. before I changed the broken vac lines I would have to let the car sit over night, and then it would start right up. Maybe this will work for you.

 

I have in fact seen this, but the other way around. My car would start but die when warm. It then wouldnt start again till cool, like 2+ hours. The temp sensor failed LOW and made the ECU think it was -40f causing a super rich mixture.

 

thanks for the replies... if the frequency of this increases I'm gonna have to do something! My mechanic is pretty good about spending time figuring stuff out, and not charging me labor hours until they actually start wrenching...

I've gotta say, I've been pretty disappointed with my 4.2 over the last couple of years... so many things have simply failed and it's getting very expensive to keep fixing :-(

 

Check your fuel pressure. Pump and Regulator. Pumps will act intermittent (usually die when hot, work when cold).
But since your flooding I doubt it's the pump. I would definitely check the fuel regulator. Also make sure that fuel can return to the tank unrestricted.

The problem your mechanic is suggesting would be the temp sensor. That is what the ECM uses to tell if the engine is cold or hot. It also uses the MAF sensor for secondary input, but the temp sensor would have to go first. He must know that the engine is flooding and has spark. Any strange Temp gauge readings?


Check the codes via VAG-COM if it was a sensor you should have a code for it.