High Idle - on occassion

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G

gyates

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I have developed an occasional high idle issue. Most of the time idle is 750 after warmed to operating temp, but every once in a while the ide is hanging around 900 in gear and around 1200 in park. Once I turn the truck off and back on it idles normal, though it does stumble a bit low for the first few minutes after restarting. Is this the beginning of my IAC failing? All maintenance on truck is up to date, including plugs/wires, clean throttle body, etc.. Any ideas appreciated. Usually when I have had an IAC fail it has been for very low or basically no idle, but so far I have not had one fail with high idle.
 
Clean MAF and IAC, Could also do a reset by disconnecting the NEG cable only, Step on brake pedal, turn on lights and stuff, then re connect NEG cable.



Todd Z



 
As my intake gaskets aged my Sport Trac behaved like that. I replaced the upper and lower gaskets a few months back and the idle settled down after that.
 
Todd and Brett, thanks for responses.



Brett, did you ever get a CEL as the gaskets were going bad? I had the upper gasket go bad on a 1997 Explorer and I did get a CEL, as well as bad idle.



I lean towards Todd's idea about IAC of MAF since this is intermittent. This morning the idle was "perfect", staying on 750. Two days ago, on drive home, idle was high for about half the drive, then settled and was great the rest of it. Yesterday idle did not settle until I turned truck off, but was fine the rest of the evening.



But, ALL ideas appreciated. :grin:



Greg
 
Intake gasket problem was the gen1 motor. I havent heard of any gen2 gasket problems......
 
Intake gasket problem was the gen1 motor. I havent heard of any gen2 gasket problems......
Click to expand...

I believe Eddie's referring to the 2001 JOB 1 motor having intake gasket issues. I should know, I confuse the two often. :grin:
 
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"Brett, did you ever get a CEL as the gaskets were going bad? I had the upper gasket go bad on a 1997 Explorer and I did get a CEL, as well as bad idle."



Yes - as it got worse I started to get the lean code (I forget which one.) Mine is an early build job one.



The job 2s have an elbow on the pcv tube that often cracks.



http://www.explorerforum.com/forums/showthread.php?t=314670



I had tried the MAF and IAC replacement first but no joy,
 
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Thanks Brett. I have replaced the famous bad elbow already. Mine was not cracked but was collapsing at times. Somewhat of an update, the past 2 days idle has been normal, maybe even a tad low at times. And with traffic woes in the Nashville, TN area, I have had lots of time to idle while in gear. :( I have owned this truck 5 years and it now has 107k miles, but I have never been totally happy with idle since I bought it. My wife's '04 Explorer has always idled dead on 750, regardless of weather ac on or off, etc.. I still love the truck though. :)
 
My Sport Trac now idles in the same range as your Explorer. Before I fixed the gaskets it was worse during cold temperatures. I previously owned both a 1995 Ranger and 1999 Explorer with the 4.0 OHV engine and the upper gaskets started leaking on those engines at around the 120,000 - 140,000 mark.
 
As I hunt down this idle issue I have discovered that the cruise control cable, at the throttle body end, has a cracked plastic sleeve. It has cracked in a jagged pattern, not straight across. For now I have smoothed the plastic so it does not bind, but I am assuming a new cable is in my future. If anyone has instructions on replacing the cruise control cable it will be greatly appreciated. :) My only concern is the servo end of the cable, as the throttle body end is simple to unclip.
 
So I have replaced the cruise control cable. Easy job. But the occasional high idle is still resent. There is not rhyme or reason as to when it idles high, ambient temp and truck tem does not matter. In gear it normally idles @750, but when this high idle kicks in it idles around 900. In park, when high idle issue has appeared, it will idle in the 1200-1500 range. Seems to happen more often with truck warmed up to operating temp, and does not happen every day. Odd issue. All fluid levels are good, IAC is new, no fluid leaks, and I do not hear any vacuum leaks. At times it will idle high for part of my drive, then idles normal the rest of the drive. Again, no rhyme or reason, but I wonder if this is electrical in some manner..
 
Has the thermostat been checked or replaced (ever)?



If failing such that flow is restricted and heat builds-up, the idle will be raised (by software) to draw more air through the radiator (kind of messes with braking and transmission shifting, too).
 
Yardsdale, the thermostat has been replaced, but I definitely understand the reasoning. I did do one last thing the other day. I pulled the MAF and cleaned it. I sprayed every one of the elements in the MAF using MAF specific cleaner. The fluid that ran out of it was mostly clear, but there was a little dark fluid as well. Since I did this the idle has been good the past couple of days. So, here's hoping that cleaning the MAF has resolved this...
 
I think I may have FINALLY resolved this issue. And I feel stupid.. Basically it appears that I over-tightened the 2 IAC bolts and damaged the gasket. I recently ordered a replacement gasket and idle is finally perfect. So, for those that might read this and attempt to clean/replaced the IAC, DO NOT OVERTIGHTEN THE BOLTS! As you tighten the bolts, as soon as the IAC is snug and you begin to feel a little resistance on the bolt, STOP. :supercool:
 
Sounds like your over tightening created a vacuum leak...which often results in a higher idle speed.



...Rich
 

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