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Old 04-14-2009, 03:31 AM   #1
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Default Erratic Idle

My 7M idles terribly. When its cold it raises idle properly, but once warm jumps from 1000-2000 rpm's or so back and forth. I have checked the Throttle Position Sensor, the Idle Speed Control Valve and the Cold Start Injector in the way the FSM says and they all check out good... I'm lost and need to fix this, as the truck is close to ready to drive.

P.S. it is not pulling a check engine light, or any codes. Thanks for any help!
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Old 04-14-2009, 03:35 PM   #2
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Have you checked your throttle linkage? That's the only other thing I can think of.
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Old 04-15-2009, 12:11 AM   #3
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throttle linkage is smooth and free of any binding, etc... throttle does not move when the engine revs...
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Old 04-15-2009, 02:49 PM   #4
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Doe sit continuously rev up and down? If so, check your vacuum lines are not broken and are routed correctly. I had a couple switched around, took me forever to get rid of that revving...
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Old 04-17-2009, 12:45 AM   #5
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I searched the engine for some bad vacuum lines... again... and found one that hangs off the rear of the intake thats plugged with a screw. Couldnt see anywhere to put it tho, and couldnt figure it out in the FSM, so could anyone take a look for me?
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Old 05-06-2009, 12:58 AM   #6
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I checked out a couple other things with it today as well as eliminating all the emissions crap from the engine. When I unplugged the Cold Start Injector or the Idle speed control valve, the problem was still there, but when i unplugged the tps the engine revved up to around 3000 rpm and held there. Adjusting the idle screw did nothing. I think my next step will be replacing the tps, any ideas?
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Old 05-06-2009, 07:07 AM   #7
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I would recommend checking the timing first. After 2 days of checking the tps and cleaning the iscv I found out that my timing was off causing the engine to run at high rpm. But I also found out that my iscv was dead so I manually adjusted it to the right position and so far no major problems, just a bit of bogging when you let off the gas and get back on it quick.
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