Muad'Dib said:
When the engine is cold, or only been running for a few minutes the idle when in gear is actually slightly better when its fully warmed up. (Still not quite where it should be) It seems to be about at the first line if its warm or hot.
Could this be caused by a faulty 02 sensor. Ive changed it already about a year ago, but ive always been conceared about it for one reason or the other. I think because when i purchased it, the counter jock pit his fingers on the end of it...
I imagine any oil from his fingers has burned off by now. See what the input voltage to the three pole connector TPS is (should be around 4.6-4.8, most are). And then test the ground for resistance. See what your low voltage reading is throttle closed both to the TPS ground and chassis ground (back pin connector with the connector connected). The TPS adjustment is usually set up to the transmission side, the input voltages for the ECU side come from the ECU, for the transmission side from the TCU, sometimes they don't match very well. Just to see if anything is seriously out of wack. It's possible the ECU side of the TPS is way out. The ECU side of the TPS grounds through a few splices and ends up at the dipstick holder, as does the tranny side of the TPS, but the tranny side follows a different path. Check the ground rings at the dipstick holder for corrosion (oil and grease) and put them under the main ground cable.
There is an opening on the top of the TB, that goes from top to bottom, with the idle air bypass screw in the middle. It's possible it's gummed shut. If you have to remove the bypass air screw, count the turns, so you can install it back in the same position.
Block off all of the vacuum taps on the intake manifold and see what happens. The vacuum taps are all off center, so this can bias the O2 sensor readings.
Pull a couple of plugs, after a drive up the interstate at around 2000 RPM, this is usually the leanest running part of the RPM band and an indicator of the O2 function. Light grey (to off white) is good.
Double check your intake manifold bolts and the TB hold down bolts (the gasket shrinks).
Check the harness where it runs from the front of the fuel rail down the front of the motor. Hard to see in there, you may need a flashlight and a mirror. Mechanics have a bad habit of rerouting the harness after they do an exhaust manifold change or even a water pump change. The harness cooks on the exhaust manifold.
It may not be just one thing, it may be much like mine was and a bunch of small stuff, that added up to a really crappy idle.
Pull your MAT sensor out and clean the gunk of the end, carefully.
The reason for the laundry list is, this is what I did and noticed steady improvements at most every step. Mine idles great now, though just a touch low, around 500 RPM.