I found this forum doing a google search on the cold start valve problems. I have read some excellent information from the archives.

The car is VERY difficult to start, and takes a few minutes of cranking and rough running below 1000 RPM to get it to the point where I can warm the engine up by holding the RPMs up to 2000. The adventure all started when I replaced the air filter as part of my pre smog check tune up. I broke a vacuum hose off, and was to fix that hose, and replaced another rubber elbow that was cracked on another vacuum line. Long story short, my Audi didn't pass smog, and was VERY high in NOX, but passed very well in the other categories. I ran the numbers thorough the Lambda equation and it seems my Audi is running lean. I suspect the fuel pump to be weak.

For my cold start problem, I suspect the cold start valve is not working. I pulled the connector off and plugged in a fuel injector test light, and while cranking cold it didn't light up. I am not sure if I damaged any wiring while replacing the air filter, or what. I don't know what steps I should take to track down this problem. A Bentley manual is a little out of my price range at this moment, and I have a Haynes on order and should be getting it sometime next month.

 

my recomendaton is make tripple sure that you don't have any vacum leaks left ... gram a can of break cleaner and have at it ... and if you are sure that you don't have any vacum leaks than read this thread ... https://www.audiforums.com/m_390931/tm.htm

 

Thanks for the link. The thing is, once it is warm it seems to run fine, steady idle, no hesitation. The fact it runs steady after it is warmed up makes me lean away from a vacuum leak causing the problem. It starts fine once warm, the problem is getting it to start when cold. I will check for vacuum leaks again to make sure. Besides brake cleaner, an unlit propane torch can be used to track down vacuum leaks. I do prefer brake cleaner though.

I had been reading this archived thread https://www.audiforums.com/archive/t...-142456-1.html

 

also make sure all your temp sensors are working corectly ... because there are 3 diff ones .... and if the car dosn't know it's cold out it's not going to turn the cold start on .... but i have a sneaky suspicion that the cold start valve might spray some help start fuel into the intake regardles of temp