Intermittent Idling Problem - '98 5.4L
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Junior User
Joined: Nov 2003
Posts: 60
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From: Tyler, TX
Intermittent Idling Problem - '98 5.4L
We have an intermittent problem with our '98 Expedition where it won't idle. When this occurs, the engine will runs as long as I'm giving the engine gas, but as soon as I take my foot off the gas pedal the engine will die. I have changed the fuel filter, thinking this may have something to do with it, but there was apparently no change. I'm not sure if this is merely a coincidence but sometimes the problem will go away after stabbing the gas pedal to the floor several times while the engine is not running.
Has anyone else experienced this and have a solution? could this be related to the TPS sensor? Oh yeah, no check engine light is on.
Thanks.
Rob
1998 Expedition 4x4 5.4L
Has anyone else experienced this and have a solution? could this be related to the TPS sensor? Oh yeah, no check engine light is on.
Thanks.
Rob
1998 Expedition 4x4 5.4L
Senior User
Joined: Aug 2004
Posts: 304
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From: Connecticut
IAC valve behind the intake manifold, fairly easy to replace. Somebody said its available in auto supply and is called bypass-valve. OEM is probably much more expensive. A lot of folks (including me when I experienced similar idling issue) just clean them out using breake cleaner (the mechanical part only, not the electrical part).
Depending on how much mileage you have, you may want to replace the rubber elbow just below the IAC valve while you're on it , a lot of folks here are reporting vacuum issue there setting all kinds of engine codes. The kit (elbows and hoses going to PCV valve from two points in the manifold) is available only at dealer but cost less than $30. If you have 100k miles or more (or close), you may want to consider it.
Good luck
Depending on how much mileage you have, you may want to replace the rubber elbow just below the IAC valve while you're on it , a lot of folks here are reporting vacuum issue there setting all kinds of engine codes. The kit (elbows and hoses going to PCV valve from two points in the manifold) is available only at dealer but cost less than $30. If you have 100k miles or more (or close), you may want to consider it.
Good luck
New User
Joined: Aug 2003
Posts: 23
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I have a 98 5.4 as well and ran into the same trouble. My check engine light came on though. I replaced the IAC and still the same problem. After checking on this sight, I found the dreaded vacuum leak. There was a worn out spot on the rubber line that comes in behind the IAC on the backside of the engine.
If you order the part, make sure they give you the right one, as my dealer gave me one that looked right, but the bend on the last elbow was wrong. My guess is that it was for the 4.6 engine.
My dealer wanted an hour labor to do this job. The mechanic said it was difficult because of the rear air lines that are in the way. I did the job myself and it took me about 30 minutes and I don't consider myself a mechanic
Good luck.
If you order the part, make sure they give you the right one, as my dealer gave me one that looked right, but the bend on the last elbow was wrong. My guess is that it was for the 4.6 engine.
My dealer wanted an hour labor to do this job. The mechanic said it was difficult because of the rear air lines that are in the way. I did the job myself and it took me about 30 minutes and I don't consider myself a mechanic
Good luck.
