high idle
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high idle
99 ranger, 2.55 speed. truck idles with very high rpm's when driving and shifting gears. have changed the AIC, mass air sensor. throttle position sensor and still does it. the AIC has been changed 5-6 times in 6-8 months as parts store kept telling me it was that. what can i look at, check, etc
thanks
steve
thanks
steve
Cargo Master
Joined: Feb 2002
Posts: 2,414
Likes: 22
From: Tucson USA
I disconnected the IAC on my truck years ago when it was doing the same thing. Using a code reader at a independent shop they traced the issue to a wire somewhere in the bundle but that was about it. Disconnected the thing and raised the idle via the adjuster to around 750 and have not had any problems since. Disconnect yours and start and hold the idle up a little and see if it runs without problem.
Laughing Gas
Joined: Apr 2004
Posts: 819
Likes: 2
From: Northern Maine
I had a 1988 Tempo one time with the same issue. I turned the idle screw in and unplugged the IAC but it didn't start well when cold. I then installed a toggle switch on the IAC. I would turn it on to help with cold starts and then shut it off after it warmed up. My daughter ran that car that way for several years. We just ignored the CEL.
Moderator
Joined: Jan 2004
Posts: 13,851
Likes: 111
From: SW Va
Welcome to FTE
I like the after the MAF sensor unmetered vacuum/air leak idea. A mucked up/stuck open PCV valve & it's poor fitting/dry rotted, leaking PCV system plumbing/fittings, especially it's rubber elbow, belong on your suspect list, as the elbow likes to split/crack in the bend & that's a vacuum/air leak After/not monitored by the MAF sensor.
Seeing as a vacuum/air leak not monitored by the MAF sensor can cause a high idle that's so bad it can't be compensated for by the IAC, it'll also corrupt fuel trim, so post up what your ELM scan tool says the short & long term fuel trim Numbers are looking like & post up All trouble code Numbers it finds.
A dirty/varnished throttle plate od & or it's bore, can cause the throttle plate to stick open/not seat, such that it leaks so much air around the plate that the IAC can't compensate.
Intake manifold & gaskets & faulty vacuum lines probably belong on the suspect list too, if the above don't pan out. So, with the engine off, maybe consider giving them a "smoke test", by blowing smoke from a "Swishers Sweet" cigar into a intake manifold vacuum line connection & look for a leak where the smoke exits.
More thoughts for consideration, let us know what you find.
I like the after the MAF sensor unmetered vacuum/air leak idea. A mucked up/stuck open PCV valve & it's poor fitting/dry rotted, leaking PCV system plumbing/fittings, especially it's rubber elbow, belong on your suspect list, as the elbow likes to split/crack in the bend & that's a vacuum/air leak After/not monitored by the MAF sensor.
Seeing as a vacuum/air leak not monitored by the MAF sensor can cause a high idle that's so bad it can't be compensated for by the IAC, it'll also corrupt fuel trim, so post up what your ELM scan tool says the short & long term fuel trim Numbers are looking like & post up All trouble code Numbers it finds.
A dirty/varnished throttle plate od & or it's bore, can cause the throttle plate to stick open/not seat, such that it leaks so much air around the plate that the IAC can't compensate.
Intake manifold & gaskets & faulty vacuum lines probably belong on the suspect list too, if the above don't pan out. So, with the engine off, maybe consider giving them a "smoke test", by blowing smoke from a "Swishers Sweet" cigar into a intake manifold vacuum line connection & look for a leak where the smoke exits.
More thoughts for consideration, let us know what you find.
Posting Guru
Joined: Feb 2001
Posts: 1,016
Likes: 1
High Idle TSB 00-3-5
<HR>
00-3-5, Publication Date: JANUARY 31, 2000
FORD:
1998-99 TAURUS SHO
1998-2000 RANGER
ISSUE:
A high idle may occur on some vehicles. This may be caused by a poor electrical connection at the wire harness (-12B637-) to Throttle Position Sensor (TPS).
ACTION:
Splice into wire harness (-12B637-) just after the TPS with TPS Connector High Idle Service Kit. Refer to the following Service Procedure for details.
SERVICE PROCEDURE
Verify the concern vehicle exhibits a "high idle" condition when depressing the clutch or shifting between gears for the Ranger or when shifting between Park and/or Neutral for Taurus SHO. If high idle condition is not exhibited, proceed with other driveability diagnostic fix procedures. If condition is present, obtain a High Idle Service Kit (XF1Z-15K607-AA) and proceed by following the instructions found within the service kit.
OTHER APPLICABLE ARTICLES: NONE
WARRANTY STATUS: Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage And Emission Warranty Coverage
DEALER CODING
OASIS CODES: 203200, 617400, 619400
<HR>
00-3-5, Publication Date: JANUARY 31, 2000
FORD:
1998-99 TAURUS SHO
1998-2000 RANGER
ISSUE:
A high idle may occur on some vehicles. This may be caused by a poor electrical connection at the wire harness (-12B637-) to Throttle Position Sensor (TPS).
ACTION:
Splice into wire harness (-12B637-) just after the TPS with TPS Connector High Idle Service Kit. Refer to the following Service Procedure for details.
SERVICE PROCEDURE
Verify the concern vehicle exhibits a "high idle" condition when depressing the clutch or shifting between gears for the Ranger or when shifting between Park and/or Neutral for Taurus SHO. If high idle condition is not exhibited, proceed with other driveability diagnostic fix procedures. If condition is present, obtain a High Idle Service Kit (XF1Z-15K607-AA) and proceed by following the instructions found within the service kit.
OTHER APPLICABLE ARTICLES: NONE
WARRANTY STATUS: Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage And Emission Warranty Coverage
DEALER CODING
OASIS CODES: 203200, 617400, 619400
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