2000rpm Idle - 89 Comanche 4.0

[jon1998]

My Jeep idles at 1500 rpm cold and 2000 rpm warm. It runs pretty rich and is very slow. I have replaced the IAC valve, MAP sensor, CTS sensor, tested and adjusted the TPS sensor, cleaned the grounds near the dipstick and on the firewall, and cleaned around the butterfly valve in the throttle body. I have also checked for vacuum leaks in the brake booster diaphragm and the check valve, and the vacuum lines themselves. I have sprayed starting fluid where the intake and exhaust manifold attach to the block and it did not make the idle go up or down. I have checked vacuum with a vacuum gauge which said the vacuum was good. I am completely out of ideas. It's probably noteworthy to mention  bolts on the exhaust manifold were loose (I tightened the loose ones down, but it didn't change anything), could my problem be a vacuum leak at the manifold gasket?

[onlyinajeep726]

It's possible, but if you've tightened the bolts and sprayed fluid on it with no difference in RPM's, it doubt that's it.  Make sure you tighten all of them, the bottom ones especially.

[omega_rugal]

you either have a small, almost unnoticeable manifold leak somewhere or the O2 sensor is failing...

 

mine was idling out of control and turned out to be the TPS even it was reading fine last time i tested it...

[cruiser54]

How did you adjust the TPS?

 

Ever check the resistance in the sensor ground circuit?

[omega_rugal]

loose the bolts and move it all the way down...

[jon1998]

Thanks for all of the replies, 

I adjusted the TPS by taking the reference voltage of the flat connector and twisting the sensor so that the output voltage would read 17 percent of the reference voltage. I also tested it by measuring the output voltage as I moved the throttle; the number climbed gradually. I'm pretty sure I haven't checked the resistance of the ground circuit.

[cruiser54]

Thanks for all of the replies, 

I adjusted the TPS by taking the reference voltage of the flat connector and twisting the sensor so that the output voltage would read 17 percent of the reference voltage. I also tested it by measuring the output voltage as I moved the throttle; the number climbed gradually. I'm pretty sure I haven't checked the resistance of the ground circuit.

REALLY worth doing!!!!

[jon1998]

I am still pretty new to fixing anything on my jeep, especially when it comes to electrical stuff, how would I check the resistance of the ground circuit?

[MeanLemons]

Tug on the ground wires and see if it comes loose. Lol just kidding.

[cruiser54]

I am still pretty new to fixing anything on my jeep, especially when it comes to electrical stuff, how would I check the resistance of the ground circuit?

http://cruiser54.com/?p=44