1997 Ranger 4.0 Heavy Idle Surge

[GEdge]

1997 Ranger just started surging from about 200 to 1500 RPMs at idle. After running for a while (10-15 minutes) the surge settles into a range of about 600-1200 RPMs. It is significantly worse at start up if the AC is switched on, but little different after running for a while. Suggestions?

[fordfury94]

Ive had the same crap. check/clean/replace youre IAC.

If that dont work, clean youre MAF and check your IAT.

The reason its worse when A/C is on at startup is the compressor is pumping. that can even cause youre truck to cut off. just wait till everythings warmed up to turn that on.

[95silverado]

Clean the throttle body. Carbon can build up on the throttle plate and cause idle problems.

[GEdge]

Originally Posted by 95silverado

Clean the throttle body. Carbon can build up on the throttle plate and cause idle problems.

I have cleaned the IAC valve and this appears to have solved the problem. When I removed the air intake "hose" a sticker appeared on the end of the throttle body warning me not to clean it as it has a special coating. I wiped out the carbon, but did not apply any cleaner or detergent. Is there a recommended cleaning solution for the throttle body?

[95silverado]

I don't know if throttle body cleaner would be safe for your truck or not. I know you can't use carburator cleaner.

[1994RangerMan]

where is the IAC located on a 94 ford ranger?? cuz my truck reves up to about 2000 rpm's when it first starts and then drops down to 400, almost stalling out, then back up again, and so on and so forth. would that bed the same problem... ???

[ggreene1]

I also have an idle surge proble but not as drastic as 400 to 2000.. maybe up to 900 and then sometimes dies. If IAC is idle air control, I already replaced it... The problem didn't go away. Now here is the wierd part. The truck (97 Ranger w/ 4.0 liter) idles perfectly if the tank is full. Then at about 2/3 to maybe 1/2 it starts the surging... Any thoughts ???
Thanks

[Crasen]

Originally Posted by 1994RangerMan

where is the IAC located on a 94 ford ranger?? cuz my truck reves up to about 2000 rpm's when it first starts and then drops down to 400, almost stalling out, then back up again, and so on and so forth. would that bed the same problem... ???

The IAC valve is going to be just behind the throttle plate. It will have an electrical connector on it. Do not confuse it with the Throttle Positioning Sensor. If you are not sure which one it is have someone turn the key to the run position while you listen for it to move. You can ussually hear it run when you do that

[GEdge]

Vacuum leaks seem to be a common source of this problem. Fuel cap, fuel lines, etc. Turned out I finally found my vaccuum leak to be at the Intake Plenum manifold gasket.

[Crasen]

Originally Posted by GEdge

Vacuum leaks seem to be a common source of this problem. Fuel cap, fuel lines, etc. Turned out I finally found my vaccuum leak to be at the Intake Plenum manifold gasket.

Yes a vacuum leak can cause the same problem, after all an IAC valve is basically a controlled vacuum leak and when it malfunctions becomes an uncontrolled vacuum leak by allowing air to bypass the throttle plates

[ggreene1]

Hey should I put any kind of sealer on the gasket of the IAC ??

[Crasen]

If you have a gasket... That is your seal. If you need to hold the Gasket in place for installation you can use a gasket adhesive.