2000 ford explorer idling really rough

[kiranorris]

I have a 2000 ford explorer with 148000 miles on it.start it up idles fine for a min then takes off to 2000 rpms then comes down to 1000 then idles back up and comes all the way down to 500 and acts like it is going to die.while doing all this is shaking.Have had problems with rough idle and number 3 misfiring on and off for a year.changed spark plugs,just changed wires fuel filter pcv valve,throttle sensor o2 sensor had a po171and po174 found that the oil cap was not on all the way so it was sucking in air.was running fine until started it up this morning now this.what would cause this.have been told maybe the idle air control motor.i really need some help from someone who has worked on trucks please.

[shorod]

How recently did you have the P0171 and P0174? You might scan for diagnostic codes again and see if they are still present. Maybe you have a vacuum leak, bad Mass Air Flow sensor, maybe the intake air hose is not securely fastened, or maybe the DPFE is faulty (common). Which engine does your Explorer have?

-Rod

[yotermanic]

Sounds like either an IAC solenoid or a vuccum leak, a can of carb cleaner should be able to differientiate. DPFEs were junk on them, but they generally threw codes lik P0401/403. If you still throw a P0171/174, you are almost assuredly looking at a vaccum leak. It's been a moment since I left my dealership, but I seem to recall upper intake gaskets being the most likely culprit on these.

[shorod]

I think the intake manifold gaskets were only an issue with the 4.0L V6, not the V8.

-Rod

[yotermanic]

Yip, four liters had intake seal problems and V8s ate spark plug wires...and cylinder heads

[lzqtiancai]

duuuuuuuude, I have the same problem, except it only happens when it's super cold. like below freezing.
I got a check engine light on, so I took it into a shop, the code is a vaccum leak, but they couldnt find where the leak is.... so they turned the check engine light off, but it comes back on in a week!!! I got a v6, so I guess it must be the "upper intake gasket" problem.
Im pretty noob on cars, could you guys give me an estimate cost to get that replaced in a shop. or woul`d I be able to do it on my own with limited tools?

[shorod]

What was the exact code that was read? There's no "vacuum leak" code but there are codes for lean on bank 1, lean on bank 2, etc. You'll need the exact code, which will look something like P0123, then perform a search on the forum for the code. If you don't see a recent thread related to the code, then feel free to start a new thread. Another tip, some people erroneously use 'o' in the code, so you might try searching for Po123 as well.

-Rod

[cdc692003]

Rod is correct intake gasket go bad just fixed mine. Rough idle remove plenum and
replace gaskets.

[onewayblues]

Originally Posted by lzqtiancai

duuuuuuuude, I have the same problem, except it only happens when it's super cold. like below freezing.
I got a check engine light on, so I took it into a shop, the code is a vaccum leak, but they couldnt find where the leak is.... so they turned the check engine light off, but it comes back on in a week!!! I got a v6, so I guess it must be the "upper intake gasket" problem.
Im pretty noob on cars, could you guys give me an estimate cost to get that replaced in a shop. or woul`d I be able to do it on my own with limited tools?

I would suspect the IAC valve ( Idle Air Control valve) on the throttle body.