Idle surge, way up around 2k


runnert

15+ Year Member

Joined
Aug 13, 2007
Messages
33
Points
3,101
City
Colorado
Vehicle Year
1995
Transmission
Manual
I did some searches, but didn't find anything pertaining to my situation. I have a 95 ranger (4.0 manual) and the idle surges way up around 2k. Sometimes I can get it to drop back down by touching the gas pedal, but that doesn't always work. Could this be the idle position sensor and if so, is there a way to check that? I have been looking for a vac leak, but am not finding anything now. Any suggestions?

thanks, runnert.
 
Take off the IAC and see if it stops? I haven't heard of cases where it was 2k, But I did have a friend who had a 92 with a man. that was idling at 1.75k and it was a faulty IAC. I'd give that a check before anything else personally.
 
Forceful.3, Thank you, I will check it.
runnert
 
my 99 is doing kind of the same thing, when I pull up to a stop light and pusn in the clutch the idle some times stays up around 2k or it idles way down to 300 and back up around 1500 and bounces between those two. Just started doing this and I have no idea why.
 
Mine has done that some as well. But mostly is just stays up there around 2k.
runnert
 
Clean the IAC with any solvent, carb cleaner works good.

Both of these sound like vacuum leaks to me. Look at and touch all the PCV and valve cover tubing and elbows, that's a usual spot. Intake manifold gasket leaks are common on 4.0s, but that'll usually throw P0171 and P0174 codes.
 
Clean the IAC, and if that solves your problem get ready to replace it. I haven't seen cleanings work more than a few weeks to a few months. I have almost the same problem with my car, and I believe it is the IAC. I will know in a few weeks when I get around to ordering the part.

Be careful with solvents and your IAC, some solvents can damage or even destroy it.
 
Every three to eight thousand miles I remove the intake hose and clean the throttle body and butterfly with CRC intake cleaner.

Carbon builds around the butterfly and air is metered around the diameter, sometimes affecting idle.

Don't know if it was overkill but have not replaced any sensors or controllers or senders attached to the block from the flywheel forward in sixteen years. (two 02's, one MAF)

Good luck
 
Last edited:
I just replaced the IAC on my 99 this morning and it seems to have fixed my idle flucuating problems. Cost 109$ at napa and takes about 2 min to change. Also noticed I had a small fuel leak where the braided line enters the intake manifold, I had been smelling a slight gas smell once and a while I must have not gotten it tight when I put new heads on last month.
 
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