Idle Problems
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Junior Member
Joined: Feb 2003
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Idle Problems
I have a 2000 F-150 with the 5.4L engine. About 1-1/2 weeks ago, my idle was revving up to 2000 RPM, then backing down to 500 RPM then back to 2000 RPM, etc. I replaced the IAC valve, and had the battery disconnected overnight.
With the new IAC valve in, and the battery reconnected, the idle seemed to be fine for the next 2 days. Then, the truck sat for almost a week until it was driven again.
I drove the truck this past weekend, and the idle seemed to "hunt" until it found where it wanted to be. It would drop to 400-500 RPM, bounce up to about 800 RPM, then settle in at 600 RPM.
The next 3 times I drove the truck, everything appeared to function fine with the idle.
Yesterday, the wife took it to work and everything was fine until she came home, when it stalled on her when pulling into our driveway.
Today, she drove it again, and described the idle to and from work as "hunting" like I did above. Searching between 400/500 - 800 RPM until setlling in around 600 RPM.
Also, during the time that the idle is acting up by "hunting" for itself, the 1-2 upshift is harsher than normal. When the idle is functioning fine, there is no problem with the 1-2 upshift.
Not sure if the harsher upshift is tied into the idle problem or is a coincidence?
I've heard that when disconnecting the battery, the PCM needs to "relearn" driving parameters. I am guessing that since I replaced the IAC 1-1/2 weeks agao, we may have only put on close to 100 miles, but not much more than that since this is not our primary vehicle.
Suggestions?
With the new IAC valve in, and the battery reconnected, the idle seemed to be fine for the next 2 days. Then, the truck sat for almost a week until it was driven again.
I drove the truck this past weekend, and the idle seemed to "hunt" until it found where it wanted to be. It would drop to 400-500 RPM, bounce up to about 800 RPM, then settle in at 600 RPM.
The next 3 times I drove the truck, everything appeared to function fine with the idle.
Yesterday, the wife took it to work and everything was fine until she came home, when it stalled on her when pulling into our driveway.
Today, she drove it again, and described the idle to and from work as "hunting" like I did above. Searching between 400/500 - 800 RPM until setlling in around 600 RPM.
Also, during the time that the idle is acting up by "hunting" for itself, the 1-2 upshift is harsher than normal. When the idle is functioning fine, there is no problem with the 1-2 upshift.
Not sure if the harsher upshift is tied into the idle problem or is a coincidence?
I've heard that when disconnecting the battery, the PCM needs to "relearn" driving parameters. I am guessing that since I replaced the IAC 1-1/2 weeks agao, we may have only put on close to 100 miles, but not much more than that since this is not our primary vehicle.
Suggestions?
Senior Member
Joined: May 2002
Posts: 538
Likes: 0
From: Chino Hills, Ca
It can take 300-500 miles for your PCM to re-learn. You should disconnect the negative cable for around 15-20 minutes and leave your lheadight switch on, of course the light won't come on but this drains and resets the PCM. Then hook your cable back on and start the truck and just let it idle for 5-10 minutes, this allows your PCM to learn idle speed.