1999 C5 A6 avant 2.8 hot start issue
 

G'day everyone, I'm completely new to the forum and have been searching everywhere and alot of people have similar issues but can't find the answer for me anywhere. Basically I have a 1999 c5 A6 avant 2.8 quattro with 220k km's. All of these problems started about a year ago. Firstly, when the car is hot the only possible way I can get it started is to hold the accelerator flat to the floor (it cranks perfectly it just wont catch for a while). This problem goes away when the car has been sitting for a while and cold OR when the car has a full tank of gas. It also idles at around 750rpm and the car shakes quite a bit (has stalled a couple times). I've ordered a coolant temp sensor but im not sure if this will address all issues. Have checked error codes and there are none to do with the engine or fuel etc... only to do with airbag which i took out. Any help would be greatly appreciated :)

It is the coolant temp sensor. If the ECU cannot tell what the correct temperature of the engine is, it will more than likely make the fuel mix too rich or too lean to make the engine run properly at start up. I bet the problems go away when you put the new sensor in. It's a common issue but fortunately it's an easy fix.

Take a look at this thread https://www.audiforums.com/forum/gen...ng-8-a-220216/ .. I'm pretty sure you're having the same issues.