Low idle

[RichardH]

Hello:

I have 2001 4.6 2wd. Several months ago replaced the idle control valve. Recently also shop cleaned out ports leading to egr sensor on drivers side.

No check engine light on, but idles around 550 to 650, never stalls, but hunts slightly. In P or N idle is around 750 cold and hot. At a stoplight, when low idle I'll put into N and it'll bump up about 150 rpm. Transmission is in good order and fluid appears fine. Shifts fine. Turning a/c off does not effect, also have new ac compressor.

If I recall, after doing a OBDII clear of the brain, it seems to idle better for a short period, then returns to low idle scenario after a while. I do the manual's recommendation of relearning: 1-ac off, 2- ac on, 3- ac on and in D with brake on.

 

[1955moose]

Richard, what was the reason for Iac valve replacement? Was your SUV idling low/high back then? Is your idle smooth? A low or high idle can be so many things. You could have a small intake leak which is causing your low idle. Couple things to do, 1) run a diagnostics check through the data port, to see if you have trouble codes. Check engine light won't always trip, but codes will pop up on a scanner. 2) run a fuel pressure test, you could have a clog, or weak fuel pump. Hunting is caused by a lean condition, or intake leak, best way is to have a shop/ friend smoke the intake/ Exaust system. My 2000 idles around 875 in park, 700 in drive. Let us know what you find.


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[RichardH]

Howdy Moose,

I replaced the idle control due to idle and stall issues. Had to gas it with brake on to keep from stalling on way to the shop. New idle control valve fixed that issue. But it has been acting funny with low idle. Otherwise runs great. I'll put on the scan tool tomorrow and see if any codes come up.

It does not hunt bad, just a little low then recovers.

Thanks!

 

[1955moose]

Sounds like you still have a small intake leak. You can do it old school by spraying down all gaskets/ hoses, and look/ listen for a raise in idle.


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[docraymund]

Have the shop analyze fuel trim data. The pcm controls idle if all other variables are normal, then you may have a faulty pcm.