My sons 93 z28 has a rough idle when cold. Exhaust is dark, seems to be running very rich. Cooling fans always come on within 20 seconds of engine starting. Have replaced the ECT and the throttle position sensor. After 5 to 10 minutes the idle picks up and the car runs fine. I had my vette go into limp mode one time and it acted similar to this. I have heard the fans coming on is a sign of limp mode. What are the causes of this limp mode and then how does it clear.( no viagra jokes please). It throws a code 45 after running a little while. Planning to check the EGR and the idle control valve first and then looking at the fuel press. If anyone has had similar problems and cures I would appreciate to hear from you.
Thanks

 

I did and it was both my TBS and IAC( Idle air control valve) but that was on my camaro. My firebird runs rough when cold and I know it most likely needs a TBS and/or IAC but my cat is also bad. As soon as it hits operating temperature it's fine. As for the fan, my car runs hot at idle which is due to a bad radiator hose, maybe you have a small coolant leak somewhere. With my car as soon as it drives it cools right down.

 

Thx firebird lady. Last night we cleaned the EGR, TB, and the IAC passes. Will put it back together later and check fuel pressure and give it a try.
The fans come on almost as soon as the car is started. The car runs cool and have changed both water temp. sensors to confirm it. Former owner may have programmed fans to come on at startup due to common LT1 overheating with A/C in summer.

 

I think you are witnessing the electronic, "morning map?" If an egg is cracked, I would think it is cracked in the morning and if the sun came out to warm the egg, it still would be cracked.

So, if the EGR and IAC were faulty, would they not be faulty warm or cold? For the car to run perfect as to not stall when warm; as to not buck and bronco as if it was running rich; as if it was hard starting all the time... Are you trying to diagnose a computer choke process under normal conditions?