Intermittent High Idle at start 98 sohc

[torumekian]

i have an issue when i start my explorer. about 1 out of every 6-7 starts my car will go from the normal 1200 or so rpm up to 2500 rpm. its 70 degrees at night right now so its not a being cold issue. about the same time i noticed that my mileage dropped a bit, not a ton, but about 30 or miles per tank. give the tanks only 20 gallons or so thats a substantial drop. it may be pure coincidence, but i thought it worth mentioning just in case. the high idle will persist when i put the car in reverse to get out of the drive way and the idle wants to push me about 15 mph without giving it gas. after a few minutes of driving its gone, i usually only make it about a mile before i miss a red light and have to stop, and its gone by then. if i turn it off and start it again it usually wont repeat the behavior. ill throw out some other info just in case anyone finds it relevant. car has 249k on it, original eng/trans and no work needed on them so far. new thermostat housing. 98 xlt sohc

 

[Rick]

I'm thinking it could be a problem with the IAC (idle air controller). I have seen a few posts about dirty IACs causing intermittent high idle problems.

 

[crazymind]

I second the iac. It could be it just needs a good cleaning. But with that kind of mileage you might have to replace it.

 

[homerl]

I'm thinking it could be a problem with the IAC (idle air controller). I have seen a few posts about dirty IACs causing intermittent high idle problems.

Where would a fellow find this?,as I know there is no idle adjustment and my truck never idles below 900rpm in neutral.Don't mean to highjack the thread but very interesting.

 

[swshawaii]

http://www.explorerforum.com/forums/showthread.php?t=84220

http://www.explorerforum.com/forums/showthread.php?t=159261

 

[my98nnj]

Either IACV or the intake manifold is leaking, a common problem.

 

[torumekian]

ok, i'll be cleaning the IAC today, i read around on a few of the links posted (thanks for those by the way, very helpful) my one question, is there a preferred cleaning chemical? some of them said they use straight ether, some used electronics cleaner, some used carb cleaner, opinions?

 

[swshawaii]

Also important to clean the throttle body. Works well for IAC valve.

http://www.crcindustries.com/auto/?s=05078

 

[torumekian]

all right, im getting my oil changed today, (funny ill do expensive jobs that involve hours of labor but am too lazy to change my oil myself), while the lady is driving me around while they do it ill pick some of that up, and clean my IAC and TB when i get home and the engine cools off. i'll report back when im finished.

 

[torumekian]

Ok I cleaned the iac and it's drying now. I also cleaned the throttle body. Iac didn't seem particularly dirty using throttle body cleaner it was clear in moments. I tried to remove the black cap and clean the felt filter but couldn't get it off. I didn't want to break it so I gave up. Throttle body had no visible damage but was pretty dirty took half a can of cleaner abs a nylon brush to get it clean. I'll be starting it up soon to see how it goes. Will post and update after.

 

[torumekian]

well, started good this morning, but since it was intermittent i cant say quite yet that its fixed, but so far so good. started up at about 1500, and within 2-3 seconds dropped to about 1,000.

edit -12:11
3rd start now, ran an errand on my lunch just now and boths starts had same good start, just 2-3 seconds around 1500 then back to a thousand. hopefully this will solve the mileage issue that developed at the same time.