Idling too fast

First, I'd take the truck back to Ford and at least let them know that you're having problems with the work they performed. Then I would check the return spring and the throttlebody plate to make sure that is not jammed up with something or a spring is missing

My engine often idles very high. Sometimes when I drive, it idles so high I can do 5 mph or so without pushing on the gas pedal. Very often when I come to a stop the engine idles VERY high for 5-10 seconds then comes back to a normal idle. I have replaced the idle air control valve. But it did not help. What is causing this and what do I need to do?

Earl scott

I have a 98 ford ranger 2.5, 2 wheel drive, 5 speed manual. And sometimes I shift gears, pull up to a stop light or stop sign with the clutch pushed in, the engine revs up for a minute or so unless I shut it off and turn it back on or I engage the clutch. It soes this every now and then and I cant figure out why, the check engine light isnt even on. Please help!

3.0 L
car runs and drives perfectly.

But when, and only when I turn the a/c on, or turn on a climate control function that requires a/c, the idle goes through the roof to 2,000 rpms and stays there like a cruise control.

Sometimes in the morning if its not terribly hot out the problem doesnt happen. The a/c is properly charged and blows cold. I have replaced the idle control valve, and to rule out a possible vacuum leak I drove the car with the IAC removed and the IAC intake holes plugged. The problem didnt happen then. I have studied my ford service manuals searched the internet, asked friends, and got nowhere. Seems like a rare problem. I also scanned the obd and have not found any codes nor has the check engine light ever came on.

Thank you for the reply.
I tested the ect with an ohmeter and at normal operating temperature it is 2.5 k ohms.

Also, when this problem happens the engine overheats, which I am guessing is a fuel/air mixture problem as a result of the iac is being told to open too much.

If I go out and drive the car and never turn the a/c on it is fine. But after running the a/c and experiencing the problem, if I turn the a/c off, the problem still occurs and will not go away until I shut the car off and restart it.

If I am running the a/c and experiencing the problem, ocassionally if I stop at a light, it will go away, then when I get moving again and work the gas pedal a few times it will come back.

I always thought a pcm rarely goes bad.

Coolant level is normal, no the iac does not have coolant hoses, only an electrical connection.

Is there any possible circuit that is on when the a/c is on that tells the pcm to increase the idle? Could this circuit be giving the pcm too strong of a signal causing the problem?

Otherwise I would agree the problem has been narrowed down to the pcm.

This was previously a florida car and has seen tremendous a/c usage.

97 ford ranger starts and drives fine except when I coast to a stop the idle stays revved up a bit, then when I come to a full stop it settles down to normal. I'll take off, go to shift and the engine revvs up some, i'll shift gears, let out the clutch and the truck sort of lunges a little bit. It revs and idles high then settles down to normal again.
No engine light has come on.
I'v looked under the hood for loose hoses, clamps etc. Don't see anything noticible.
Read online about the EGR valve, oxygen sensor, Idle speed control motor and have identified all of those componens but I don't know what exactly they do or if
any of them need to be replaced.
Appreciate any help

PROBLEM SOLVED!

Since there was no check engine or code thrown I figured it might be mechanical.
I started the diagnosis with simple tune-up procedures.
Changed all the spark plugs and that solved the problem.
Now. Runs like normal.
Thanks for the timely and good ideas!

What has happened recently is the idle would be doing this at all times. I have read the article about high idle where it says

"I can tell you this, the oxygen sensor (02), MAF or MAP and coolant sensors are prone to this type of sensor failure."

what happened the other day is this:
i finally got a check engine light. Pulled into vatozone
and this is what it said. P0420, catalyst efficiency below threshold bank 1. Perhaps my o2 sensors, or catalytic converter may have been causing the computer to run in "open loop mode" or "closed loop" not sure which one, but a high idle condition.
Is this a possibility?
I suspect this has been causing my problem

thanks!

My '96 ranger has similar problems. The idle willl jump to 4000-6000 RPM while in nuetral, or with the clutch disengaged. The only way to bring the RPM down is to lug the engine or fry the clutch. Any other advice would be very much appreciated! Thanks

I don't know alot but i'll tell you what worked in my case.
If you have a check engine light, hook up a computer reader and identify the code. That should point you in the right direction. Mine had no "check engine" light, so I started with simple tune up stuff. All I did is change my spark plugs. A smarter guy than me told me if the plugs are worn out then the truck has to enrich it's fire/fuel mixture at idle to stay running. My plugs were 30,000 miles old and it worked like a charm. Consider changing the plugs & look at the tips & wire ends for corrosion, (white or green powder.) If mine still ran rough I would have moved on & changed the plug wires & fuel filter.
Let me know how it turns out.
River

You are not going to believe what the problem was and it couldnt be guessed a hundred times. The battery!
The battery was old as hell. It was unable to team with the alternator and support the a/c compressor load, plus cabin fan high load. So the computer goes into some kind of rescue mode, and cranks the rpms. But it went so haywire. The computer would tell the iac to go full blast.
Replacing my battery and spending the 90 bucks was the magic pill! My electrical system can now support the a/c and
it now idles so perfectly I can engine brake, and shift smoothly.

Thankfully the only other money i've thrown at the problem has been on:
4 huge ford factory service manuals, a multimeter, and a mass air flow sensor.
Oh and the iac valve I bought but then used and returned cause it didnt fix the problem. Vatozone!

Well I really feel great that I didnt go buying a new ECM. Because I was coming really close to narrowing everything else down and renderring out all other possibilities.

I just cant believe that the battery was the culprit.
Please pass this along and put it in your tech section or
things to check first section.

Thaks for some direction. I started with a tip from a buddy, and removed the throttle body and upper intake, cleaned them out really well, replaced the gaskets and reassembled. While I was at it, I replaced the EGR valve and this seemed to DRASTICALLY improve the performance. IMy next move is to actually buy a code reader, and tackle the other issues one at a time. I will most definitley be doing the tune up, and replaceing all parts as needed. Again thanks for the time to reply!