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KaBKa
Novice
Aug 21, 2006, 12:28 PM
Post #1 of 7
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Engine- rising idle
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I have a 1988 ford f-150 l-6 4.9l manual.
I have already been to three mechanics 1 of them trying to charge me $800 for doing what i had already done.
When i start it up it idles perfect sounds great problem is though after a while of running the idle gets higher and higher to the point that after about 4 or 5 miles if i push in the clutch it revs up to 3000-3500 rpm.. it slowly raises starting at about 900 rpm idle (normal) a mile or so later it will be about 1500 2 miles 2000 3 miles 2500 so on and so forth...
no engine codes
i have already checked all the vacuum lines they are fine, changed the map sensor, tps, iac. on the out side of the vacuum canister though i cannot get any sort of vacuum even with it capped off i do not know if that is normal.
The first mechanic did not tell me what he did but said he did not know what was wrong.
Second changed everything i had already changed, checked the vacuum lines i had already check, and checked the wiring i had already check. then told me it was my computer...
third just said it was probably my computer...
Thank you for taking your time to read this even if nobody has any ideas thank you
(This post was edited by KaBKa on Aug 22, 2006, 1:23 PM)
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 22, 2006, 8:05 AM
Post #2 of 7
(2163 views)
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Re: Engine- raising idle
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Is the throttle cable free to return? T
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KaBKa
Novice
Aug 22, 2006, 12:47 PM
Post #3 of 7
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Re: Engine- raising idle
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aye.. i put on a stiffer spring shortly after the problem started because it was not returning all the way... also i just realized i misspelled rising making for a very misleading title
just to see what would happen... i unpluged the vacuum line for the map sensor and caped it... it ran almost like normal except for a bit of a rough idle but i might be able to fix that by raising the idle... i put on the old map sensor with vacuum line unpluged and caped and same thing
(This post was edited by KaBKa on Aug 22, 2006, 1:47 PM)
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 22, 2006, 2:35 PM
Post #4 of 7
(2150 views)
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Re: Engine- raising idle
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I would take that cable off the intake and see how it feels and probably that's it and throw it out! If it doesn't move freely disconnected there could be some issue with the throttle plate, T
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KaBKa
Novice
Aug 22, 2006, 3:44 PM
Post #5 of 7
(2149 views)
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Re: Engine- raising idle
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ok that did not fix the problem so much as cover it up for a short while... after running for a short time it continues to idle quite rough no matter what rpm it is at...
here is a question... what effect should vacuum have on the fuel pressure reg... again just to see what would happen i disconnected the line to it and plugged it no change to the way the engine ran... put it under 25-30 *merc/in?* of vaccum with a vacuum pump and again no change in the way the engine ran...
also nothing wrong with the throttle plate
(This post was edited by KaBKa on Aug 22, 2006, 3:46 PM)
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KaBKa
Novice
Aug 24, 2006, 12:10 PM
Post #6 of 7
(2127 views)
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Re: Engine- raising idle
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replaced throttle body.. no change same problem...
The manifold stays at 25 in-hg at idle and goes to about 28-30 when reved to 3500 rpm... if that matters
is there anyway the fuel pressure reg. could fail and not allow any gas through to the return line without any other symptoms?
oh... and 96 straight 6 was put in about 7 months ago
(This post was edited by KaBKa on Aug 24, 2006, 3:06 PM)
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KaBKa
Novice
Aug 30, 2006, 9:21 AM
Post #7 of 7
(2108 views)
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Re: Engine- raising idle
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Now i feel pretty stupid... i decided to change out the gaskets for the intake.. when i was taking the lower half of the intake off i got to cut my and up decently.. somehow i managed to get a slit in it on the underside coming back from where it mounts to the engine going back about 2in and side to side about 3/4 of an inch woulda been able to find it the easy way had it made any noise but it sounded normal no whistling or sucking air... no idea how it happened but in anycase thought i would come back and post what it was with a questoin... if i feel stupid for not finding thing then wtf should i say to the mechanics that looked at it?????
and thank you for your time and responses
(This post was edited by KaBKa on Aug 30, 2006, 9:28 AM)
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