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05-28-2011, 05:28 AM
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Ford Tough
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Join Date: Nov 2010
Posts: 361
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Engine racing
Recently my truck has been experiencing a "racing" engine. It has been happening sometimes when I have my foot off the accelerator and slowing down for a stop sign, or stopped at an intersection. Almost like the throttle sticks. I have used cleaner on the throttle body and linkages. Any ideas?
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1992 Ford Ranger XLT, 4.0 L, Auto.
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05-28-2011, 06:37 AM
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Banned
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Join Date: Mar 2010
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Re: Engine racing
Check the IAC, I ruined mine when I cleaned it so I had to buy a new one and it wasnt racing anymore
Last edited by Clinton; 05-28-2011 at 06:58 AM.
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05-29-2011, 07:23 AM
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Ford Tough
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Join Date: Nov 2010
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Re: Engine racing
Quote:
Originally Posted by Clinton
Check the IAC, I ruined mine when I cleaned it so I had to buy a new one and it wasnt racing anymore
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How did cleaning the IAC ruin it? I took mine out and cleaned it with carb cleaner a couple months ago and just lately started having trouble now.
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1992 Ford Ranger XLT, 4.0 L, Auto.
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05-29-2011, 07:26 AM
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Re: Engine racing
I used a cleaner with a solvent, somehow it wrecked it. When i put the new one on it ran fine. I should have read the chilton manual first, thats how I realized I messed up.
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05-29-2011, 07:31 AM
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Ford Tough
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Join Date: Nov 2010
Posts: 361
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Re: Engine racing
Quote:
Originally Posted by Clinton
I used a cleaner with a solvent, somehow it wrecked it. When i put the new one on it ran fine. I should have read the chilton manual first, thats how I realized I messed up.
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Is there a way to test it first, before I replace it? Like with a volt meter or something? Oh yeah, another thing. Sometimes it will backfire through the TB on the first start-up but it hasn't seemed to jump timing.
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1992 Ford Ranger XLT, 4.0 L, Auto.
Last edited by appletonbill; 05-29-2011 at 07:39 AM.
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05-29-2011, 12:27 PM
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Diesel Truck & Coach Tech
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Join Date: Dec 2010
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Re: Engine racing
An IAC is a linear stepper motor I believe, so I don't know if there is a way you could test it. Maybe if you knew what resistance range it was supposed to have, you could check it with a DVOM....disconnected from the vehicle of course.
Is your engine running poorly otherwise? If so I'd also be looking for a vacuum leak.
I need a new IAC for my '90 Mustang 5.0L because I can never get the thing to idle right, and I've adjusted the throttle stop screw so many times but it makes no difference.
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2011 Ford Ranger Sport 4x4
4.0L SOHC
5 Speed Manual
MBRP stainless catback
"Air Box Mod" with K&N drop in
GlowShift Oil pressure & Volts in A pillar pod
T-bar crank to level
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05-30-2011, 07:43 PM
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Better than Avg Mechanic
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Join Date: Jan 2011
Posts: 183
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Re: Engine racing
Unplug the IAC and see if the idle speed drops. If it doesn't, there's a really good chance you'd got unmetered air (aka a vac leak) getting into the engine.
Also, pull off your intake and make sure the throttle body butterfly is closed completely. If it's not, there's the source of your racing engine.
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2000 XLT 4WD 4.0L OHV, 5 spd, Alabama Cylinder heads, Delta Cams Valve Train and Pushrods, JBA Headers, KKM Cone Air Cleaner, BBK Throttle body, Dynomax Cat-Back exhaust, Summit Racing drilled front rotors w/ EBC pads, Cobra rear disk brake conversion w/ Hawk pads, 8.8" 4.10 Traction-Lok
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05-31-2011, 11:45 AM
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Ford Tough
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Join Date: Nov 2010
Posts: 361
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Re: Engine racing
Quote:
Originally Posted by Gunner
An IAC is a linear stepper motor I believe, so I don't know if there is a way you could test it. Maybe if you knew what resistance range it was supposed to have, you could check it with a DVOM....disconnected from the vehicle of course.
Is your engine running poorly otherwise? If so I'd also be looking for a vacuum leak.
I need a new IAC for my '90 Mustang 5.0L because I can never get the thing to idle right, and I've adjusted the throttle stop screw so many times but it makes no difference.
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No. She runs normal most of the time. This is a sporadic thing. It happens sometimes while I am just coasting or stopped at a light.
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Quote:
Originally Posted by Badmotorfinger1
Unplug the IAC and see if the idle speed drops. If it doesn't, there's a really good chance you'd got unmetered air (aka a vac leak) getting into the engine.
Also, pull off your intake and make sure the throttle body butterfly is closed completely. If it's not, there's the source of your racing engine.
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Ok, I'll try that, thanks.
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Quote:
Originally Posted by Badmotorfinger1
Unplug the IAC and see if the idle speed drops. If it doesn't, there's a really good chance you'd got unmetered air (aka a vac leak) getting into the engine.
Also, pull off your intake and make sure the throttle body butterfly is closed completely. If it's not, there's the source of your racing engine.
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Is it possible that the TPS could be bad?
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1992 Ford Ranger XLT, 4.0 L, Auto.
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05-31-2011, 12:05 PM
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Better than Avg Mechanic
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Join Date: Jan 2011
Posts: 183
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Re: Engine racing
Quote:
Originally Posted by appletonbill
Is it possible that the TPS could be bad?
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Possibly, but it's been my experience that a bad TPS will throw a code. Plus, if the engine is racing it needs an air source and the TPS has no control over that.
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2000 XLT 4WD 4.0L OHV, 5 spd, Alabama Cylinder heads, Delta Cams Valve Train and Pushrods, JBA Headers, KKM Cone Air Cleaner, BBK Throttle body, Dynomax Cat-Back exhaust, Summit Racing drilled front rotors w/ EBC pads, Cobra rear disk brake conversion w/ Hawk pads, 8.8" 4.10 Traction-Lok
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05-31-2011, 03:42 PM
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Ford Tough
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Join Date: Nov 2010
Posts: 361
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Re: Engine racing
Quote:
Originally Posted by Badmotorfinger1
Possibly, but it's been my experience that a bad TPS will throw a code. Plus, if the engine is racing it needs an air source and the TPS has no control over that.
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Ok. That makes sense.
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1992 Ford Ranger XLT, 4.0 L, Auto.
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06-17-2011, 01:15 PM
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Ford Tough
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Join Date: Nov 2010
Posts: 361
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Re: Engine racing
UPDATE: I replaced the IAC and I still have the problem of high idle, only now it is worse because it idles high all the time now. I have to literally
stand on the brakes when I pull up to a stop. WTH?
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1992 Ford Ranger XLT, 4.0 L, Auto.
Last edited by appletonbill; 06-17-2011 at 01:18 PM.
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06-18-2011, 10:14 AM
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Ford Tough
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Join Date: Nov 2010
Posts: 361
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Re: Engine racing
UPDATE: It was low on coolant and transmission fluid. I topped everything off and now everything seems to be operating normally. I do need to replace some hoses though.
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1992 Ford Ranger XLT, 4.0 L, Auto.
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