anyone want to take a guess?

[bobstrat]

recently my bronco has developed a new issue. the first time i start it, she runs fine. idles normally, no driveability issues.

if i turn it off and restart, like stopping for a cup of coffee, she idles real low almost to the point of stalling. in nuetral around 700-800 rpm. in drive 500-600 rpm. it started off rather sporadic. maybe one time then a week with no problem. now its getting pretty regular. back to two footed driving or sweating in the checkout line while i leave her running.(weird how one little vehicle fire changes you.) my drive to work is at least an hour each way. the problem only occurs at operating temp. if i run to 7-11 (three blocks) no problem. ive been too lazy/crappy weather to mess with it. that will change friday. three day weekend should cover the "more involved than i thought" factor. i havent taken the time to check for codes, but i thought i would throw this out for guesses. so go ahead guys (except you, roushstang :-& #036; ) .... i will report back with the results.

oh and since i have a spare IAC, i switched them out yesterday. no difference. could still be that circuit, i didnt do any troubleshooting.

 

[blackhoss89]

hey there just wanted to respond that mine is still acting crazy. some times when it idles correctly, when i turn the key it goes straight to 2000 then drops to about the range you talked about 500-600 then bog down to nothing, if i keep it running then it is ok. other times the truck starts fine and idles around 850-900, normal,then after a couple minute or two it will run all the way up to 1700-2000,just wanted to update and let you know that mine also does it. good luck B)

 

[madmax]

I had some idle problems with my 5.8. It would idle normally at first, then it would start climbing. I changed the IAC and still had the same problem so I tried running with the damned thing unplugged using the set ***** in the throttle body to set the idle. Had to give it some gas starting but after a couple seconds it was fine. Later I tried re-plugging in the IAC and it worked fine. No idea why its working now or why it wasn't before, but at least there is a workaround.

I'm guessing the root problem is the computer sending the wrong signal to the IAC, I should mention I'm not as familiar with the 302's as I am with the 351's. 302's have mass air sensors right? Might be worth trying unplugging the IAC and then setting the idle with the ***** on the throttle body (ignore that do not adjust warning). That should somewhat fix the problem for ya, also it helps to have somebody start the truck and hold the engine at 800 rpm while you adjust the ***** till it touches the plate (I swear that will make sense when you look at the throttle body).

 

[Seabronc]

Check this article out in Ford Muscle magazine on Surging Idle. It could be your problem.

Good luck,

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