Occasional Issue at Startup

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Mar 26, 2011 | 11:21 PM

jd1083

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Joined: Feb 2011

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Occasional Issue at Startup

Like the title says my '01 F250 5.4L occasionally acts weird when I first start it up. It starts fine but immediately drops to 500 RPMs. Every once in a while it will sit at 500 RPM for a second or two then race up to around 1500-1800 RPMs then drop back down to the normal 1000 RPM, but sometimes it will stay idling at 500 RPMs and run a little strange for a few mins. What could be causing this?

Mar 27, 2011 | 10:19 AM

jh818

Cargo Master

Joined: Jul 2009

Posts: 2,885

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From: Chino, California

Check IAC valve?

Mar 28, 2011 | 07:15 PM

ddesens

Freshman User

Joined: Mar 2009

Posts: 27

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From: Ontario, NY.

Check for broken or cracked vacuum lines on the intake manifold also. Pcv valve new?

Mar 28, 2011 | 09:22 PM

jd1083

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Joined: Feb 2011

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I checked most of the vacuum lines and they're all in good shape, haven't gotten to check the IAC valve yet. The truck runs fine besides the occasional strange issue at startup. I'm leaning towards the IAC but a local mechanic said that if the IAC were bad that it would throw a code and cause the SES light to come on, and it hasn't come on yet.