pesnemesis

would the ECM cause the idle to go up and down and also cause the engine to stall?
Note: all sensors have been replaced.

go-part

It could be the ECM, its alot more likely to be the IACV though..

pwb

My ZJ did the same thing when the IAC was bad, it was running ok but after i did remove the battery for some time the ECU got reset and then i didnt know how to use the bad IAC. I replaced the IAC and TPS, still a litle problem and replaced the TPS againg and then everything was ok. I think there is a lot of bad quality parts out there, the first TPS i tried fell apart. I also cleaned my TB since it was full of "dirt"/black oil.

pesnemesis

Replaced = iacv,tps,tcs,eas,map, tested fuel pressure.
I bought a rebuilt ecm to see if it fixes it. We'll see.i'll let you know.

Willys55

you don't mention if it's the 4.0L or the 5.2L. Vacuum leaks can cause the idle to fluctuate and the 5.2L will stall if the IAC can't control minimum idle air flow. In either case it would not be uncommon for a replacement part to be faulty, i.e. the IAC or TPS that you said you replaced.

In regards to the IAC, a battery disconnect or reset min air flow and IAC relearn should be done when ever the IAC or TPS are replaced. Best way is with a suitable scanner, however disconnecting the battery terminals and momentarily touching the two cables together for a few seconds will clear all the ECM/BCM data and cause the ECM/PCM to perform the relearn, however transmission and fuel trim data will be lost doing that and it will shift funny until the TCM relearns the shift pressure points.

pesnemesis

it's a 5.2L V8, thanks for the tip!

Bustedback

The 5.2 V8 has a plate with a gasket on the bottom of the plenum, the gasket can get blown out and then you will get an internal vacuum leak. It can also suck oil into the intake and cause an oil consumption problem. The best way to check it without pulling the intake manifold off would be with a smoke machine. Pump smoke into the intake, if you have smoke coming out of the oil fill cap, you gat a leaking plenum plate. Make sure to cap off the PCV nipple on the manifold first though.

pesnemesis

will the gasket leak make the engine idle go up and down intermittently or consistently?
I do have an oil consumption problem.

dave1123

If you've got the time and a place to work, pull the intake off and check it out.

Bustedback

It can make the idle fluctuate.