rough idle
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New User
Joined: Jun 2006
Posts: 8
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From: sylvania, OH
rough idle
When i first start the truck it idles at 2000rpm's, when it is warm it idles the same but comes down to a really rough idle. When it is up to speed and you let off the gas the rpms jump from 1000 to 1500 4 or 5 times, then goes to normal. it is a 1999 f250 superduty 4wheel drive with a 5.4. Auto zone's computers say its running lean on both banks. ive replaces the iac, egr, tps, o2, maf sensor, pvc valve, and checked for vaccume leakes with carb cleaner. any help would be appreciated. thank you.
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Joined: Jul 2002
Posts: 42,561
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From: Long Island USA
I don't think the TPS is adjustable on these motors. I could be wrong.
Check the plumbing for the PCV valve. There is an elbow in it, the rubber deteriorates and it can be very hard to tell it's bad.
Otherwise, check everything else between the throttle body and the MAF.
Also, the ports in the throttle body for the IAC can be clogged.
Check the plumbing for the PCV valve. There is an elbow in it, the rubber deteriorates and it can be very hard to tell it's bad.
Otherwise, check everything else between the throttle body and the MAF.
Also, the ports in the throttle body for the IAC can be clogged.
FTE Leadership Emeritus
Joined: Sep 2000
Posts: 23,174
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From: Stephensville WI
OK, time for some automotive 101 rules.
If you change something on your engine (like an MAF) and that engine suddenly has new symptoms (like running real lean) the new part is probably the cause. 99.999% of the time there is a direct path between cause and effect. These things are not coincidental!
Also, just because a part is new does not mean it is good.
If you change something on your engine (like an MAF) and that engine suddenly has new symptoms (like running real lean) the new part is probably the cause. 99.999% of the time there is a direct path between cause and effect. These things are not coincidental!
Also, just because a part is new does not mean it is good.
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