1987Comanche Posted November 14, 2009 Share Posted November 14, 2009 This one is a bit odd. I finally got the '90 on the road and have noticed an odd quirk that's a bit baffling. When driving around town the truck idles at what I would consider to be a normal 1000RPM or so. It hunts around a bit but by and large idles ok. I'll ride a few miles on the highway at 70mph or so and, upon exiting the freeway, the idle speed sits at 1500 RPM and will do so until I shut the truck off for a few minutes. I cleaned the throttle body out with TB and air intake cleaner, cleaned the Idle Air control valve and even swapped in my spare IAC. Absolutely no change. Any thoughts/suggestions? The '90 is a Renix 4.0, AX-15, 4WD. Link to comment Share on other sites More sharing options...
Pete M Posted November 14, 2009 Share Posted November 14, 2009 Weird. I would probably start with vacuum leak hunting. Link to comment Share on other sites More sharing options...
A-man930 Posted November 14, 2009 Share Posted November 14, 2009 Mine has done this same kind of thing for quite a while. I mostly solved mine by re-adjusting the idle speed screw that someone had messed with, but it still does it to some degree... Link to comment Share on other sites More sharing options...
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