Idle speed

[AvlAndrew]

Hey guys, question.
What does a 1990 Bronco2 like to idle at normally, ac off?

Mine is at 1100 rpm.

thanks!

 

[fastpakr]

Fully warmed up, it ought to be more like 700-800. I don't know exactly, but that's typically on a sticker on the core support.

 

[RonD]

1990 B2 2.9l engine with automatic transmission in Park should idle at 750-800rpm after full warm up, say 5 to 8 minutes
Manual trans 650-700rpms

It will idle at 1,100 or so when cold, then slowly drop down as it warms up

Higher idle can be failing IAC Valve, vacuum leak or failing ECT sensor

Locate IAC Valve on upper intake, has 2 wire connector
Warm up the engine
Let it idle and unplug the 2 wire connector on IAC Valve, RPMs should drop to about 500(barely running) or engine may stall, either is GOOD it means IAC Valve was working and no vacuum leaks

If idle stays high then IAC Valve may be stuck or you have a vacuum leak
Remove IAC valve and clean it then try test again

 

[Cees Klumper]

Mine idles at around 700 warmed up, everything is well sorted.
Could bad ignition timing also cause high idle?

 

[AvlAndrew]

Yes, I corrected the timing to 10’ BTDC and she is running idling much better.

 

[Cees Klumper]

Thanks! I like it when my hunches turn out to be correct.
Diagnosing can be the hardest part of fixing any problem.