Surging or loping idle
Thread Starter
|
Member
Joined: Apr 2002
Posts: 13
Likes: 0
From: Apopka, Florida
Surging or loping idle
Help Needed: MONEY-PIT
2001 F-150 Supercrew:5.4L, Fowmaster, K&N.
While driving and in cruise engine rpm increases and decreases. When coming to stop rpm remains elevated approx. 1000 to 1200. After complete stop approx. 5-10 seconds idle drops to 800, but does not go to 600-650 as it was originally. This is with or without A/C. While sitting at idle and in park or neutral the idle is not steady, surges between 800 to 1200 rpm.
Have changed the plugs, boots and springs, fuel filter, cleaned throtle body, IAC, EGR and air filter prior to the conditions above.
Have taken to Authorized Ford shop for analysis. They have thrown everything at it but the "lug nuts". They gave up the first day. Went back the second day and they tried a new throttle body (no sucess). They took a break from the truck and tried again this afternoon by shotgunning the problem with a new IAC, TPS. The readings from the diagnosis show no lean burn associated with a vacuum leak. They want to try a PCM next, but if does not work, the PCM can not be returned.
Any ideas would greatly be appreciated.
2001 F-150 Supercrew:5.4L, Fowmaster, K&N.
While driving and in cruise engine rpm increases and decreases. When coming to stop rpm remains elevated approx. 1000 to 1200. After complete stop approx. 5-10 seconds idle drops to 800, but does not go to 600-650 as it was originally. This is with or without A/C. While sitting at idle and in park or neutral the idle is not steady, surges between 800 to 1200 rpm.
Have changed the plugs, boots and springs, fuel filter, cleaned throtle body, IAC, EGR and air filter prior to the conditions above.
Have taken to Authorized Ford shop for analysis. They have thrown everything at it but the "lug nuts". They gave up the first day. Went back the second day and they tried a new throttle body (no sucess). They took a break from the truck and tried again this afternoon by shotgunning the problem with a new IAC, TPS. The readings from the diagnosis show no lean burn associated with a vacuum leak. They want to try a PCM next, but if does not work, the PCM can not be returned.
Any ideas would greatly be appreciated.
Technical Article Contributor
Joined: May 2004
Posts: 6,509
Likes: 6
From: Georgia on my mind...
I'd inspect the PCV tube running from the passenger's side valve cover to the rear of the throttle body. Surging/erratic idle usually comes from unmetered air getting into the engine somewhere.
Member
Joined: Jan 2006
Posts: 34
Likes: 0
From: Mechanicsburg, PA
There are some holes in your throttle body probably that run down into the intake manifold (at least there is on my focus) try cleaning those out my friend had the same problem with his focus and he cleaned a bunch of oil residue and crap out of them and it ran good.
Last edited by boostedzx3; Feb 15, 2006 at 08:56 PM.
Senior Member
Joined: Sep 2005
Posts: 2,618
Likes: 0
From: Atlanta, GA
I had that exact problem on my mustang a few years back. Its one of two things, an air leak as stated, or an EGR related issue. Mine was a combo of both and I used an EGR simulator to fix it, although I don't think those are available for the new ones
Thread Starter
|
Member
Joined: Apr 2002
Posts: 13
Likes: 0
From: Apopka, Florida
The repair shop eliminated the EGR, TPS, PCV, throttle body and associated hoses. For some strange reason, today the truck is running somewhat normal, it is idling a little high (800-900) at stop lights now but will drop off to 600-650 after a few seconds. I have heard this thing has an adaptive computer that learns as you drive. I did have the battery disconnected when I replaced the plugs and boots. But it does not seem right that it would take this long for it to calm down to where it should be. 