I have a Dodge Magnum 5.9L V8 (from a 2000 Dodge Durango) that was swapped into my 2000 Jeep Wrangler TJ back in 2006. It took me a while to figure out what was specifically wrong, but about 5,000 miles ago, I suffered the dreaded plenum plate/gasket failure and got a lot of crankcase oil into the intake. I have now completed the work to pull my intake manifold and upgrade the crappy factory plenum plate with a beefy 1/4" aluminum plate from APS Precision, along with the newer design plenum plate gasket. The good news is that my 5.9 is running great now with plenty of power, no pinging, and no more repetitive P0171 "system too lean (bank 1)" fault codes.

However, I am still having an intermittent problem with a high (~2000 RPM) or surging idle about 25% of the time after the engine is up to operating temperature and I have come to a stop. I have no idea if it is the cause, however, I am wondering about the condition of the original idle air control (IAC) motor unit on the back side of my throttle body (which I carefully cleaned but did not replace). If the IAC is acting up, could that cause my intermittent high or surging idle?

If it's not the IAC, would any malfunctions with the following contribute to my intermittent idle problems?

- Intake manifold air temperature (IAT) sensor
- Throttle position sensor (TPS)
- Manifold absolute pressure (MAP) sensor

If anyone has any ideas as to what might be causing my idle issues, I would sure appreciate getting the input.

Thanks,
Don

 

yes map or tps would be my guess

 

IAC should cause the idle to be all over the place. My old 5.2 in 1996 would swing back and forth between 700-1200rpm's.

What about O2 sensor, every Chrysler product I've owned has started acting up around the 70k, 140k mileage mark.

 

Check For vacuum leaks when up to operating temperature, check IAC, and EGR valve.