RRC High Idle

Swedjen2

Well-known member
Sep 12, 2018
591
126
California
1990 RRC 14CUX. The engine starts fine, but after it gets to normal temp., the idle stays at 1100 and won't go down. It used to drop to around 5-600.
This just started last week after several years of running fine.
Any suggestions appreciated.
 

Blueboy

Well-known member
Apr 20, 2004
3,035
377
Back in the USA; Rockwood, PA
1990 RRC 14CUX. The engine starts fine, but after it gets to normal temp., the idle stays at 1100 and won't go down. It used to drop to around 5-600.
This just started last week after several years of running fine.
Any suggestions appreciated.
Throttle position sensor are known to be problematic. Stepper motor also could be an issue.
Also try the search feature of the site. Feel sure this issue has been discussed before.
 

StangGT5

Well-known member
Feb 4, 2019
132
43
Atlanta, GA
I had the opposite problem with my 92. It had a very weak idle when warmed up, so weak when putting it in gear it would almost stall and I could hear the snorkle sucking like a dying animal. I replaced the idle control valve, nothing changed. Swapped the temperature sensor (not the sender, the gauge worked) and all is well.
 

discostew

Well-known member
Sep 14, 2010
7,276
837
Northern Illinois
1990 RRC 14CUX. The engine starts fine, but after it gets to normal temp., the idle stays at 1100 and won't go down. It used to drop to around 5-600.
This just started last week after several years of running fine.
Any suggestions appreciated.
The first thing you need to do is make sure the throtttle isn't being held open by the cables. Next set the minimum idle. If you have the air tube to the IAC clamped off and can't idle it down with the idle air bleed screw then you have a big vacuum leak.