A little back story, bought a 90 XJ 4.0, it had an issue with stalling immediately after I would start it. Turns out the TB needed to be cleaned which fixed that issue. Now after cleaning the TB I have a very high idle when the engine warms up. I thought at first maybe I messed up the IAC as I cleaned that too. Went out and bought a new IAC and no difference. I have checked for vacuum leaks by spraying TB cleaner and placing my hand over the TB (the engine did die). I have tested my TPS which seemed to be working correctly, I had a smooth transition of readouts on my voltmeter. I unplugged the MAP sensor and the engine drops to a rough idle and almost stalls (I hear this means it is working correctly).

I checked the screw in the TB and it is flush with the wall of the TB. There is a small gap in between the wall and plate of the TB and if I press down fairly hard to close this gap the rpm's do drop but it still idles high.

I do not have a tach (only idiot light gauge) so I cannot say how fast it's idling but I'd guess 2k+ (high enough that I can release the clutch and go through 1st and 2nd gear without touching the gas pedal).

I could use any suggestion.

 

Do a search in CF for "high idle", you'll get a bunch of posts to look at, remember the search funtion is your friend. This is a common problem with these motors. Getting intake cleaner in the tps will kill it, and just because its giving you voltage, doesn't mean its the voltage the motor/AIC/ECM needs (1/100th of a volt can make a difference!). When I first got mine, I had to replace the AIC motor, TPS, and replace the intake/exhuast gasket, because a couple of the bolts had backed out. Now I idle at 850-900 when cold and about 550 when warm.

 

try and look again for cracked vacuum lines if not connect your ohm meter and read the tps 3 wire circuit black is ground lead and the grey wire should read around 5.0 the blue wire in proper calibration should ready 4.15-4.2..good luck