rough idle

[Silversage]

hey guys, i have a 2000 NM pajero exceed 3.5l Auto its having a idle problem only after it has been sitting for a while 4+ish hours.

When i start it it turns over fine first go, but then the idle surges really bad it goes up and down from like 2rpm to 900 rpm (sometimes stalls) this will last around a minute then its fine, except its acceleration does seem a little sluggish.
i can make the problem seem not existent if i apply a small amount of constant gas, it all runs smooth, take my foot off and like crap again, but only for a short while

What i have done so far with no fix.

Changed Leads, Valve cover seals, tube seals, spark plugs, Cleaned the air flow Sensor (off the air box), Cleaned the throttle body, Changed air filter, fuel pump tested

i really dont think it is fuel related, more so air or air/fuel mix

Only other things i can think of changing is:
O2 Sensor
Step Motor
or maybe a vacuum leak?

whats your thoughts?

[woody]

Mine does a similar thing when starting from cold but only for a couple of seconds, then it runs fine

[dolphin]

sounds like the main ECU is having troubles reading an Engine Idle setting,this is why your getting the up / down rpm,s. i would have said maybe a Vacume Hose Leak but if this only occurs after the said 4 hours of sitting i doubt its a rubber hose issue.
you need to check firstly the 2 x units which are positioned on the main throttle body, both have plug in wires attached and are sort of servicable unless there day / s is numbered. start with cleaning up the inner plug fittings firstly to these 2 x units [ idle speed and stepper motor ] just to make sure all connections are nice and clean then disconnect the main car battery for 30 minutes so the ECU can re adjust any issues and see how things go. don,t worry we will get your engine idling like a rolls.

[Silversage]

Well i have Cleaned the Step motor plugs, and Reset the ECU, still runs like a bucket of shit when i start it.

Also today seems the problem evolved, i can now (not always) stall the car by turning the air-con on if idling

[christianungapen]

Hey I'm having the same problem did you resolve it?