I have an 84 5.0 LX. It has a CFI setup.
The issue I'm having is that when the car reaches full operating temperature the RPM's wont lower to the correct 550 in drive, 1000 in park. If I bring the car to full operating temperature then shut off the car for 10 minutes, then I re start it runs at the correct 1000 in park and 550 in drive. It will run correct all day long. Even if I shut down for a few hours and let it get completely cold, it will start back up at the correct RPM's. But when the car sits overnight or longer, the first run I have to finesse to get the RPM's right by driving, shutting down then restarting.
The choke functions correctly. It is vacuum controlled by the same solenoid and vacuum line that controls the dashpot which controlls the RPM's. It seems to me that the vacuum is supposed to cut off to the dashpot and the choke kickdown when the car reaches full operating temperature. I believe the issue is that the ECM isn't sending the signal to cutoff the vacuum to the dashpot when the car is warmed up. I can drive for an hour or 90 minutes and the RPM's will not come down until I shutoff the car for 5 to 10 minutes, then magically the RPM's are spot on after I restart.
The CFI setup is a beast to be tamed for sure, but when it runs right it purs like a kitten. I replaced all the solenoids and vacuum lines when I got the car a few years back. I do have a spare ECM I can swap just to check. I dont want to play with the curb idle because the car will find it's idle if I run, kill and re-run. If the curb idle was off, it would be off all the time.
It never was like this before. Now the car sits most of the time in the garage, but there was a time when I commuted in this car every freezing cold NY morning and it always warmed up and kicked down its idle gracefully without me needing to mess around.
Any ideas on this?
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