Hi all! I read theses posts on a daly basis but this is the first time I'm asking for help!
I have a 2.8L V6 engine, A6 C5 platform.
I love this car as my baby since I'm a pure DIY guy! I know every nut on it... But this time I'm facing a hard-to-find problem, so any advice will be very appreciated to avoid some trial and error.
My car starts fine when it is cold. Always. But after a short ride and engine warmed, if I stop for a few minutes (10 min or more) it refuses to start (some times starts all fine!!!). I turn the key, the engine cranks strongly, I have sparks (I removed one cable and could see the spark jumping to the chassis), I have fuel (so much that I can smell it. Yes, after insisting to start, it smells like sulphur/gas). After being upset for a few times with the situation, I decided to insist keepeng the key on until necessary. Well, in this case, with the throttle all way down (I'm not sure it it realy makes difference but works) and keeping the key turned for about 5 or more seconds, the engine starts to run but with very difficulty. If I stop turning the key, it dies and the fight starts again. If I insist keeping the key turned on, it starts, go to 1000, 2000 rpm, drops to 400, goes up againg and then (maybe) starts... (full throttle). Some times OK, some times not. Wow, what a fight!! If I give up and let it rest for about an hour, it starts normally like a doll. I hope I described the situation well. If you have questions please ask. Just to complete: I have new spark plugs, new oil, new air filter, sparks, goog cables, gas and replaced all the vacuum hoses. Thaks a lot for reading all this!!!

 

Likely the coolant temperature sensor...

https://www.audiworld.com/tech/eng108.shtml

 

Concur...unless there are codes stored to indicate something else. Pull codes first.

 

I'll check the coolant sensor. I'll be very happy if it's just that

I just ordered an OBDII to USB cable from Ebay.
Hopefully when it arrives I'll able to pull the codes (it's so cheap!!???) using VAG-COM. As soon as I do this, I post it here.
But, this will take one week or more to arrive...
Meanwhile, any ideas will be very appeciated!
Thanks a lot!

 

Hi, is there a way to test the coolant sensor? I mean something like unplugging it to avoid the problem. Or a resistence metering. I knwon it is a little complicated since the problem occurs only sometimes and when everything is hot! But who knows...

Thank you!

 

Coolant sensor is cheap, easy to replace, and a common failure item. In the time it would take you to test it you could have it replaced. Buy a new 0-ring and clip to go with it.

 

I'll do that and then post the result here.

Thanks a lot!

 

UPDATE: I changed the coolant sensor and since then, the problem did not happen. I tried but could not reproduce it again. Hopefuly it's solved! Thank you guys very very much! I hope some day I can help you as well!! Thanks!!