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  #1  
Old 12-09-2017, 10:44 AM
Woodtroll Woodtroll is offline
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Join Date: Aug 2015
Posts: 154
Default Odd Idle Behavior with Clutch In?

The truck I have had for about two years has begun exhibiting an odd idle characteristic. It is a 2008 2.3L 5-speed, about 135k miles.

At road speed, when I push in the clutch to coast to a stop at a stop sign, gas station, etc. the idle will drop to 450-500 RPM as soon as I push the clutch in, which causes the truck to occasionally stall. I got to watching the RPMs as I coast, and found that if it doesn't quit completely on me when the idle drops initially, when the road speed eventually drops to about 5 MPH the idle hops right back up to 750-800 RPM where it should be.

Experimenting further, I tried rolling off from a stop on a slope. From parked position, at 750 idle, I rolled off with the clutch in. When I got rolling about 6-7 mph, the idle dropped to just under 500 RPM. What the heck?

When the truck first started stalling out (before I caught the RPM drop) I replaced the spark plugs and coil pack; I had put new plugs and wires in it right after I bought it as well. This really seems more like a programming issue though, since the idle is affected by the road speed at a very specific and repeatable 5-6 MPH. I don't think a defective IAC would cause this repeatable problem, would it?

Any ideas or suggestions would be appreciated!
Regan
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'86 2.3L 5-Speed Supercab, dark blue; usually a daily driver for 22 years. Great truck but getting tired at 355,000 miles!
'08 2.3L 5-Speed Supercab, Pueblo Gold; just acquired, hope I get 350k out of this one!
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  #2  
Old 12-09-2017, 06:50 PM
stateranger stateranger is offline
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Default Re: Odd Idle Behavior with Clutch In?

A dirty or bad iac can do that. It wouldn't hurt to clean the maf sensor too while checking things.
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  #3  
Old 12-10-2017, 03:44 PM
99Ranger376 99Ranger376 is offline
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Default Re: Odd Idle Behavior with Clutch In?

Quick thumb nail way to check your IAC when the truck is idling unplug the IAC if it almost stalls out it’s working, no change in idle it’s dirty or gone bad, I know a lot of people on here try cleaning the IAC , personally I just replace them when they aren’t working, they are relatively inexpensive and replacement is a 5 minute job.


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2011 Ranger XLT 4x4 3.73 8.8" Trac-lok #1 T-bars, K -springs, LineX bedliner, General Grabber AT2's, Tonnopro tri-fold, CoverKing Realtree AP seat covers, OEM pre-keys, axle spacers, Bilstein 4600's, Hellwig AAL. Ziebart Undercoat
'98 Ranger XLT 2WD (sold)
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  #4  
Old 12-17-2017, 04:28 PM
Woodtroll Woodtroll is offline
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Default Re: Odd Idle Behavior with Clutch In?

Thank y'all. That bug, virus, or whatever this site seems to have persistently makes it hard to get on here sometimes. I appreciate your advice and will take a look at the AIC.
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'86 2.3L 5-Speed Supercab, dark blue; usually a daily driver for 22 years. Great truck but getting tired at 355,000 miles!
'08 2.3L 5-Speed Supercab, Pueblo Gold; just acquired, hope I get 350k out of this one!
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  #5  
Old 02-16-2018, 04:39 PM
Woodtroll Woodtroll is offline
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Posts: 154
Default Re: Odd Idle Behavior with Clutch In?

Just an update for anyone who might have this problem in the future. I have been working on this issue a little at a time as I had free time.

I tried replacing the IAC first, with no change. Cleaning the throttle plate and MAF (neither of which appeared very dirty anyway) made no difference. Next i replaced the throttle position sensor, which appears to have fixed the problem.

Thanks for your suggestions, I appreciate the help!
Regan
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'86 2.3L 5-Speed Supercab, dark blue; usually a daily driver for 22 years. Great truck but getting tired at 355,000 miles!
'08 2.3L 5-Speed Supercab, Pueblo Gold; just acquired, hope I get 350k out of this one!
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