Ok so i feel like a total noob! I replaced my IAC, TPS, and redid all my grounds per cruiser54's writeup. And even added 3 extra grounds. So voltage at both is 4.98 and if it idles up i can unplug tps and it drops. Oh tps was set wth snapon scan tool to spec but cnt remember what spec was....i think .840ish? But today i had the tps unplugged and it did the high idle thing so i unpluged the iac no change. Could i possibly have a voltaage issue to iac that will hold it open? I test the voltage and its 4.98 always but dont know what makes it adjust the idle. Help!! Ive used multiple iacs with the same issue after a day or 2.

 

Did you replace the throttle body gasket?

 

Try setting the TPS with my instructions on the flat 3 wire connector.


RENIX TPS ADJUSTMENT
Before attempting to adjust your TPS be sure the throttle body has been recently cleaned. It's especially important that the edges of the throttle butterfly are free of any carbon build-up.
IMPORTANT NOTE: With the Key OFF, and using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS. The letters are embossed on the connector itself. Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it parallels the valve cover and also over near the MAP sensor on the firewall. If you see more than 1 ohm of resistance, or fluctuation in your ohms reading, some modifications to the sensor ground harness will be necessary. The harness repair must be performed before proceeding. I can provide an instruction sheet for that if needed.
MANUAL TRANSMISSION:
RENIX manual transmission equipped XJs have only a flat three-wire TPS mounted on the throttle body and it provides data input to the ECU. It has three wires in the connector and they're clearly embossed with the letters A, B, and C. Wire "A" is positive. Wire "B" is ground. Key ON, measure voltage from "A" positive to "B" ground by back-probing the connectors. Note the voltage reading--this is your REFERENCE voltage. Key ON, back-probe the connector at wires "B" and "C". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For example: 4.82 volts X .17=.82 volts. Loosen both T-20 Torx screws attaching the TPS to the throttle body and rotate the TPS until you
have achieved your desired output voltage. Tighten the screws carefully while watching to see that your output voltage remains where it is supposed to be. If you can't achieve the correct output voltage, replace the TPS and start over.
Sometimes, after adjusting your TPS the way outlined above, you may experience a high idle upon starting. If that happens, shut the engine off and reconnect your probes to B and C. Start the engine and while watching your meter, turn the TPS clockwise until the idle drops to normal and then rotate it back counterclockwise to your desired output voltage.
AUTOMATIC TRANSMISSION: RENIX automatic transmission equipped XJs have a TPS with two connectors. There is a flat three-wire connector, same as the manual transmission vehicles have, and it is tested the same as the manual transmission equipped vehicles, as outlined above—FOR ALL ENGINE MANAGEMENT RELATED ISSUES.
However, the automatic TPS also has a square four-wire connector, clearly embossed with the letters A,B,C, and D. It only uses three wires and provides information to the Transmission Control Module. THIS SQUARE FOUR WIRE CONNECTOR IS USED FOR TRANSMISSION/SHIFTING RELATED ISSUES ONLY. Key ON, measure voltage between "A" positive and "D" ground. Note the voltage. This is your REFERENCE voltage. Back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be eighty-three percent of your REFERENCE voltage. For example 4.8 volts X .83=3.98 volts. Adjust the TPS until you have achieved this percentage. If you can't, replace the TPS and start over. So, if you have an automatic equipped XJ your TPS has two sides--one side feeds the ECU, and the other side feeds the TCU.
FOR AUTOMATIC TRANSMISSION RELATED ISSUES: Check the square four-wire connector side of the TPS.
If you have ENGINE ISSUES check the flat three-wire connector side of the TPS.
For those with a MANUAL TRANSMISSION--the TPS for the manual transmission XJs is stupid expensive. You can substitute the automatic transmission TPS which is reasonably priced.
Revised 09-22-2012

 

Yeah gaskets are new. I rebuilt the motor like 6k ago. This has alwaysbeen kind of an ongoing problem even b4 the motor. Ill mess with it and itll go away for a month or more. But now everything is brand new a few times....i just want to get to the bottom of it. Ill set the tps again, ive done it cruisers way and with the scan tool. But ill give it 1 more shot and cross my fingers! Ill report back to...thanks guys

 

Where did you buy the TPS from?

 

Last one came from napa. First 2 were from oreilly [schucks].

 

Did you do the sensor ground TEST as described in the TPS instructions?

 

I did a few times. But im goin out here in a few, after it warms up to freezing and pull everything off and start from scratch. Ill post a few pics and descriptions of what im doin and u can correct me if needed. Do the iac and tps work in conjunction, as in one will automatically adjust to the other? Im just curious. Oh i forgot to add earlier, the tps and iac have their own ground, and the 02 and stuff is on another.

 

Possible vacuum leak?

 

Ok so i went and started from scratch....grounds are good as tested per cruisers write-up. Tps adjustment-input voltage was 4.95v so 4.95x.17=.8415 so set to .841v. Ran awsome until operating temp was reached and idle slowly started creeping up to 2.5k rpms. Shut off and restarted, instantly shot up to 2.5k again. So per adjustment procedure adjusted tps clockwise until idle dropped to normal....but it never did. Unplugged tps and idle dropped too normal. The one thing i did notice was the port for the iac sounded like a jet engine so placed my finger over port and idle immediatly dropped to 500 rpms. So reset tps and started guess what....high idle again! No vacuum leaks. Is there a reason the iac pintle would be stuck in the open position? It is also brand new 2 times from napa. Im open to suggestions now. If i unplug the tps it use to idle low but was plenty driveable but now it will idle down and then on the next startup will shoot up to 2.5-3k. So i think tps is not it. I have 1 iac that the pintle is stuck with the port closed off and the idle is low but ok. Like 7-800rpm. So possible problem with electrical at ecu? But im on ecu #2. What tells the iac how much air to let bypass? Long winded i know but ive been f'n with this for years and itll go away for a while then come back. And ive ran new grounds, pigtails, ect ect. Theres just something controling the iac thats messed up i think?!?!

 

Power brakes? How they working? A bad diaphram in the booster will do this also.

 

Cruiser54,

Maybe he has grounding issues like you helped me through. Check for resistance in the sensors. You may have to open up the wire loom and cut and solder the 5 horrible factory grounds for all the major sensors.

 

I wonder if someone messed with the butterfly stop screw on the throttle body at one time. It should die when you cover the air hole for the IAC.

 

Possibly. The TB is a used one that i got from a running crash jeep like 2 years ago. I did notice the silicone is gone off the set screw. Ill reset it just in case. And whe i block off the iac port it will die sometimes, mostly i can keep it running by allowing some bypass of air. The grounds in the harness are redone and soldered and a 5th wire from that to chassis ground.

 

The screw I'm referring to is on the passenger side and is allen head in a recess.