Hi!

I'm currently hunting the last engine problem after the major tune up (which worked wonders )

When I drive a longer trip over for example the highway and get to the first traffic light my Firebird won't hold the idle and nearly/go out suddenly. This never happens in the city and doesn't seem connected to the temperature or something...
Afterwards if I restart the engine the problem just disappears (sometimes I need a second restart at the next stop)

Any ideas what could cause this?

 

Do you ever have stuttering acceleration or coasting in lower rpms? Something similar was happening to mine, and it turned out to be the throttle position sensor.

 

Sorry for the late answer, nope, no stuttering, I had this issues a lot but got rid of them thanks to new spark plugs etc.

I've measured the tps some time ago (was also my main suspect for the rough idle) but it all checks out voltage wise...

 

Bad EGR valve? During the highway cruise it gets activated, then hangs open for a bit, displacing the idle mixture. Then when the engine stalls or during the restart, the valve manages to close.

 

Hmm That could be it!!!

Thank you, I will try to clean it! (If I find some instructions for that, alternatively I will get a new one)