High Idle

[clc4912]

I know this has been a reoccurring issue, but thought Iwould throw mine out there and see what you think.

I have a 99 3.0 that is having some idle problems. It idles too high at times. I have checked for vacuum leaks and replaced the IAC with little improvement. It will idle high and then slowly begin to drop. If I rev the engine slightly, it will stay high for a moment and then begin to drop but not all the way back down to normal.

I even thought that it was a faulty IAC that I put in so Iwent back to the auto parts store and they replaced it, but same problem. The MAF isnew as well.

The truck has 60,000 miles on it. Anyone have any ideas on what Ineed to check? All help would be greatly appreciated.

 

[Green Mazda]

If it never drops wear you want it, then turn down or losen the idle screw, it is right beside the throttle cable under that plastic cover.mine is a 99' and it seemed to be idleing a lil high so i turned mine down yesterday.

Also it could be as simple as the throttle has gummed up a little under the hood, happens on my 88' s-10 all the time

Now my question to you is how high are we talking1300..1500.. 2000rpm or higher
that can help narrow things down.
good luck!

 

[clc4912]

It is not that far from normal. My main concern is that it does not return to normal as quickly as it should. When I shift gears, it will remain high before it drops down. The time in which it takes to drop sometimes varies.

 

[Earl43P]

We need some clarification.

Is this truck new to you?

Is this high idle present ONLY while rolling? If so, it's NORMAL. The idle should drop to ~800 rpm as you come to a stop (uses the VSS signal). The PCM props up the rpm while rolling to aid with smoother shifts. Mine will sit @ ~1100 rpm as long as I am rolling. Come to a stop and it drops to 800. That's normal behavior.

Have you had the battery disconnected? If so, it may have to re-learn the idle strategy. You can force it to by starting the (already warmed up) truck, never touch the gas, let it idle for 5 min. Then select AC on and repeat for 5 min. (If it were an automatic transmission, you would then idle for 5 min in Drive and 5 more in in Drive with AC on.)

I strongly suggest you DON'T adjust the TB "idle" screw unless you are replacing the TPS and following a published test procedure where you backprobe and monitor the TPS signal.

I do suggest you verify that the TB plate is closing completely when the gas pedal is released (doesn't need to be running while you check it). A lot of times it gets gummed up and doesn't fully close. Check that. If it isn't acting consistent, I would suspect the TB plate not fully closing. I clean mine with SeaFoam (a sticker says not to clean the TB - it has a protective coating. I figure Carb/Choke cleaner may be too harsh. Not sure what Ford wants you to use.)

 

[Viva*the*Ranger]

Hey thanks Earl, that's some handy knowledge!

 

[Green Mazda]

HEY EARL
Just wondering why not turn back the idle screw, i just did yesterday 1/8th turn...will it harm something? if so i will go turn it back. It's just my tuck would idle at around 1100-1200 siting still and that seemed too high.