Run Away Idle

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Feb 23, 2012 | 09:49 AM

MikeB 88

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Fleet Mechanic

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Run Away Idle

2000, 2.5L standard transmission. IAC replaced about 2 years ago, DPFE sensor and vacuum hoses replaced early last summer. Truck has been running just fine until I washed it last night. Went to work, and when coming to a stop and pressing in the clutch, engine starts to race without coming back to idle. Had to turn the truck off in order to get the engine from racing. Same thing on the way home. What else can/should I be looking at? I did not open the hood to wash the engine off, so it can't be water from the wash.

Thanks,

Feb 23, 2012 | 08:17 PM

98range

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Sorry but you need another IAC valve. I have put 3 in my 1998.

Feb 23, 2012 | 08:21 PM

MikeB 88

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Fleet Mechanic

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Thanks for the input

I really hope that it's not going to be a 2-3 year time change item.

Feb 24, 2012 | 12:28 AM

michigan66

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From: Dexter, MI

Check your present IAC. If it is dirty, clean it with with an approved cleaner (not carb cleaner) and see if that helps. And if it is dirty (black stuff in it, try to determine what is dumping stuff into the IAC. For instance, it may be time to replace the PCV valve.

Feb 24, 2012 | 06:12 AM

97ranger xlt

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From: FL

a bad pcv valve will cause a high idle and not throw a code.

Feb 24, 2012 | 07:34 AM

MikeB 88

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Fleet Mechanic

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Thanks for the PCV info. I have changed that early last summer also. I didn't change the hose for it, as it looked good. Maybe that has gone bad since.

Feb 24, 2012 | 09:00 AM

tomw

Logistics Pro

Joined: Jan 2002

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From: suburban atlanta

Washing a car or truck usually makes it run better, get better mileage, ride smoother, and have more pickup. Waxing even increases those results. Beware filling the fuel tank, as vehicles have been known to die whenever they get a full tank. Must be overjoyed???
I don't think that washing your truck made the idle speed change. I would do as the others have suggested about cleaning, and I would also inspect all the vacuum lines and connections under the hood. There should be a base 'diagram' showing the routing and connections on the radiator support or the underside of the hood. One other thing to inspect is the 'bellows' section of the air intake system that allows for flexing and engine movement on its mounts. They have been known to break and only leak when the engine is moving. May not fit these circumstances, but worth inspecting any way.
I have had an IAC on a 3.8 keep the rpms up more than I would have expected. It only happened intermittently, so I have ignored it so far. If it re-occurs, I will clean the IAC and see what happens.
tom