1986 Trans am 305 lb9/700r4/2.77
So here’s my problem when I start the car up the idle will go right too 1200+ and keep climbing to about 18-1900 and I can’t get it to go down, then after driving for a while , when it gets put into park it will shoot up to almost 2000 and not come down so when you shut it off it will “diesel” sometimes where it keeps sputtering after car is off, i have tried so many things to fix this put I can’t nail it I’ve changed the IAC, TPS, O2 sensor also have check for vaccum leaks with propane and nothing, it’s very annoying banging it drive or park constantly, I was thinking maybe the timing but I had set it so it was dead on. Please help this is my daily car and really want to figure this out
Distributor?,EGR?

 

Did you set the timing with the est cable disconnected ?

 

Yes, timing set right, im really lost its a on and off thing i noticed that sometimes it will idle fine when you start it up other times it will shoot up to almost 1800 and sit there. i was thinking maybe my egr is stuck open a bit, im gonna check for vaccum leaks again when i get home, i have no idea what it is?