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Old 06-03-2005, 22:31   #1 (permalink)
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Question High Revs when at an idle?

I've got an '01 3.8L V6 manual trans Stang that just started acting strange when sitting at an idle and when I engage the clutch.

Any time I take the car out of gear it will rev up to about 3000 RPM and stay there. This morning on my way to work I had the thing in 5th and just took my foot off the gas to slow down for traffic and the car kept going at about 75MPH. The cruise control was off. Honestly, the car was speeding up EVER SO SLIGHTLY...

I called some parts houses and was told to try changing out the Throttle Position Sensor. I did so tonight and it's still doing the same thing. Although it's not quite as bad as before. It only revs up to about 2000 RPM now.

I am wondering if anyone has had this problem and what they did to correct it.

Am I looking at buying a new computer for this thing? If so, I think I'm going to cry... I just don't have to dough...

Thanx for the input...
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Old 06-04-2005, 04:44   #2 (permalink)
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Re: High Revs when at an idle?

I dunno if its even remotely close, but my Mark VII was acting 'kinda funny' like this, here the throttle-to-trans kickdown cable was binding...perhaps its just your linkage/cable/or even carpet tangled up at the pedal. hopefully its some 'freebie' thing like this.
I kinda doubt the TPS would do it, as if it failed I think the mixture would just go awry- it wouldnt let any extra air into the throttle. If Ford has idle air valve(like my 85 v6 camaro) those have a notorious habit of getting carbon buildup and sticking- on a chevy its a little motor/screw/plunger that provides secondary air inlet to adjust the idle speed- when mine gets sticky it tends to idle high...had to pull/clean it a couple times over the last 20 years. good luck!
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Old 06-04-2005, 12:09   #3 (permalink)
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Re: High Revs when at an idle?

I'm not sure how a carburated vehicle can compare to one that is sixteen years newer and using fuel injection.

I went ahead and checked this linkage and could find nothing bound or hanging up the cable... I did find this link. The person that posted it has the same problem that I'm having at the moment.

Mine is also running just fine when cold then it will act up after it gets warm...
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Old 06-04-2005, 14:23   #4 (permalink)
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Re: High Revs when at an idle?

Quote:
Originally Posted by Viddar
I'm not sure how a carburated vehicle can compare to one that is sixteen years newer and using fuel injection.

...
the camaro is multiport fuel injected, air idle control motor is part of the bosch injection system- and Ive been told this is a common problem...no idea what Ford EFI uses...my f150 may have a similar system- but Ive honestly never even looked at it...12 yrs old never even tuned it up yet...air/oilfilters only parts ever put into it- watch me jinx myself- it will probably die next time I drive it :)
if I get a chance later I'll snoop under the hood on my truck to see if Ford uses one also- I'm kinda guessing they do, as dont know how else computer could control the throttle unless its fully electronic/servo type like 05 mustang....
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Old 06-04-2005, 19:29   #5 (permalink)
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Re: High Revs when at an idle?

I know there were several different versions of Camaro put out that year. I assumed that yours was carburated. My bad...

I think I've got the problem solved now though. I went and replaced the TP sensor and the IAC soleniod... After that, I reset the computer by disconnecting the battery while the key was in the "on" position. Hooking things up after about 30 minutes I found it to be running just fine while the motor was still "cold"...

I drove around for a bit to warm things up and found not only that this problem had been solved but I've now got better throttle response, lower cruising speed RPMs (in turn, better gas milage) and when I engage the clutch, the RPMs "kick down" faster than I ever remember them doing in the past.
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Old 06-05-2005, 05:44   #6 (permalink)
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Re: High Revs when at an idle?

Quote:
Originally Posted by Viddar
I went and replaced the TP sensor and the IAC soleniod....
IAC Solenoid- I assume that stands for Idle Air Control...I guess ford must use a multi step solenoid/ratchet device instead of a motor? Bosch had a small 'stepper' type motor to adjust the inlet...glad you got it fixed up- injection is really great, but some systems have a lot of obscure/hidden sensors...my camaro had a 'map' sensor failure code in the computer, but something with build date/plant or something was wrong- it doesnt have one...problem ended up being mass airflow sensor- only ever had to replace that one part, and clean the air idle control a couple times in 20 years...never said that about a carbureted engine :)

ps- both my 89 mark vii and my 93 f150 I *suspect* have bad throttle position sensors- truck occasionally has a 'stumble' at that point just off idle where gas pedal spends 90% of its time, lincoln runs fine but gets check engine light at same place(going over a bridge on way to work everyday) both vehicles are fine if pedal moved least little bit...I think the TPS is just a fancy potentiometer, and that eventually the carbon/brush wears thru ... I play around with PLC's a lot at work, and hope to someday build a homebrewed injection system based on an Aromat(now Panasonic) brand PLC- have built some pretty cool little machines/gages using analog I/O and think it would be pretty easy to do...just need to hook up a strip chart recorder to one of the cars to get some baseline numbers to shoot for...maybe someday...
If the TPS is indeed a potentiometer, it might be better to replace with a non-contact hall-effect magnetic sensor...the little old mechanical gyro in my old rc helicopter uses hall effect and man are they accurate...
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