High idle right at startup...
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Freshman User
Joined: Mar 2011
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High idle right at startup...
I have a 1989 f150 300, 5spd, 140000miles, 2WD....same truck I'm having the missing at startup issue. Its always done this though. When I start it revs pretty high...I'd say 1500 or so then settles down..I HATE starting engines fast on cold mornings. I've heard ALOT of Fords do this. It idles find after it revs back down. Is there a way around this?? It does it nearly everytime...not everytime but close. Way higher than I'd like. Settles back down after only a few seconds. What causes this?? I've cleaned the IAC very well and no vacuum leaks. If I unplug the IAC it idles WAY down....probably to 500 or a little lower. But is still smooth. What causes the initial high idle?? I wish I could keep if from doing that...That reving up when its 50 degrees and lower scares me. Thanks again guy! Any information would be appreciated. Full tune up done also and cleaning of throttle body and IAC in last few weeks.
Elder User
Joined: Nov 2009
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It's a normal function of a ford engine, they all do it. No need to be scared, be more concerned that you are using a good oil! In my mind it is like fuel enrichment in a jet engine. It does this until the combustion cycle stabilizes to prevent the motor from dying on start up.
Lead Driver
Joined: Feb 2002
Posts: 7,962
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From: Greater Austin, Texas
My 300 did this everytime I started it whether it was hot or cold. I never did find out what caused it and it was annoying. I would expect it to idle high when cold and then drop to normal, but it shouldn't do it when the engine is warm.
The 460 I put in it's place doesn't do it at all, even when it's cold. I like it that way much better.
The 460 I put in it's place doesn't do it at all, even when it's cold. I like it that way much better.
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Freshman User
Joined: Mar 2011
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yeah I understand the high idle...just like the kick up on carbs and high idle lever on boat motors...but I'd rather it die a couple times that rev up when I start it...normally when warm its not nearly as high...Just doesn't seem like a good deal when cold. I run mystic 15w40 synthetic in my 300. Guess its more annoying than anything.
Elder User
Joined: Nov 2009
Posts: 890
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I don't think you can go wrong with the Mystic but if you are worried about cold starts I would take it down to a 10w30 and use a Motorcraft filter for the anti-flowback valve. Right now you're running diesel oil, which by the way works wonders in the old IH 347.
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jetman4
1997 - 2006 Expedition & Navigator
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Dec 29, 2003 11:45 AM
