Just put a new engine in my car. It's an s5 TII engine with the emissions removed. When it is cold and hasn't been started that day it will crank and die instantly for 4 or 5 tries. Once the 5 try I can get it to stay running but I have to hold it at about 2500 or 3000 rpms to get it to keep idle and it has a miss for about 1 minute and then will idle and run fine and very strong. What could cause this?

 

Any ideas?

 

when you say emmisions removed what all did you take off. i had the same problem after rebuilding my 88 s4 n/a i found that the BAC valve was sticking due to a carbon buildup. once i cleaned it the car started and ran fine it was real annoying all summer this year having to hold the throttle for the first minute or so. anyways if you took it off that would deffinatly cause your problem the bac is used extensivly at idle and cold start(it varries the amount of air for different manifold conditions) without it you need a way to adjust the air for cold start(you dont really need an idle air motor) a manual choke cable and valve would solve your problem but im assuming its not a racecar and youd get annoyed with it so id say go to a wrecker and get one because they're 780 bucks new. hope that helps ya, ps the rest of the emmision system is fine to remove and i recommend it because it is fairly ineffective at controling emmisions however only about half the crap you see is emmisions the rest is engine control and you should try to keep it because it will keep your engine running better. (ps with a little modification you can use an idle air motor from anything) but if your not looking for drivability and you just wanna car thats real fast take it all off and strip it right down.

 

the fast idle cam and BAC valve are there to stabilize idle during cold operation.