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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