DESERTXJ206

IV got a 90 Cherokee 4.0l that I'm having issues with. When I originally got it had a low fluctuating idle between 300-750 rpms. Depending on engine temp. So I took off the throttle body removed all sensors including the tps and I AC. I thuroughly cleaned the TB and iac. I put it all back together started it up and it was idleing at around 1800-3000rpms. So I adjusted the tps to specs and that calmed it down to about 1500rpm. So at first I replaced the I AC and didn't change anything. Today I replaced the tps and it still is idleing high. I'm not sure what's next. I do have a bad exhaust leak at the very back of the manifold. I'm not sure if that changes things. Please help me out thanks.

Mlcantin

Have you reset the computer?

JeepDeep

Leak in exhaust manifold can mess with air/fuel ratio. RPM changes slightly with air/fuel ratio changes but not that much. Vacuum leak possibly? I would pay close attention to any possible leaks around the TB since things changed (got worse) when you cleaned all of it. Spray carb cleaner around the area while the engine is running and listen for RPM changes.

cruiser54

Did you replace the throttle body gasket?

What instructions did you use to adjust the TPS?

XJ.89.Limited

Check the lines going into the back of the air box. There should be a 90 bend and a straight bend hose up towards the top. The 90 bend if disconnected will make it idle higher. Also, a crack in the manifold or leak around the seal will do the same. If it was idling between 300-750 you should have never touched it. They aren't very high revving engines. Mine idles the same way and I never had a problem. Often times messing with the TB sensors messes it up and it takes a few times to get it back to normal. Use THROTTLE BODY cleaner whenever you clean it, not carb cleaner. I'm sure one of our resident renix experts will chime in with more info. Also, Mlcantin, you cannot reset the computer on a renix. That is why a renix is special. Welcome to the world of no diagnostic check, no idiot light, no tuning abilities, one o2 sensor, and the most confusing yet simple and reliable fuel injection system the XJ came with.

XJ.89.Limited

cruiser54 is a renix genius.

DESERTXJ206

Devided the input by output and got it set at .830. I h

DESERTXJ206

Devided the input by output and got it set at .830. If I remember according the write up I saw. I didn't clean the throttle body due to low idle it was gummed up. But didn't know about the tps until after I started looking into my issue. IV tried Carb cleaner spraying it around and have got no response. Today I replaced the tps and set it the same way I adjusted the old one. Here's my thereoy: previous owner messed with the idle set screw, I can tell cause the threads are all chewed up from like pliars, it had a much larger gap than my 88xj. So I may try to adjust that back in or bent the metal piece to (fake) the throttle body to think the set screw is in further. But it used to kind of surge before I cleaned the throttlebody, once engine was warm it would pulse back and forth at a light.

DFlintstone

Until Cruiser wakes up! 3;30 AM? I believe you want that stop so that the plate just doesn't touch the body. Not hitting, and about zero clearance.

Just in case you are looking for something to do;
That rear manifold bolt has a habit of loosening. On anything like that you NEVER want to tighten only one. It can warp/bend, even crack things. If I found that any that where easy to reach where loose, I'd pull the air cleaner and tighten them all, starting in the middle and working out towards the ends. I'd go over three times, a tad tighter each time. It's a bear of a spot to get a torque wrench on them all. Just don't ape on it. If its firm and not turning, no point in going on to break it, a REAL *****. The rearmost bolt underneath takes a little doing, but it can be done with the right extension(s?). For that very back one by the firewall I use way long extensions (18"), with a swivel at the socket. Anyway, that's a good thing to check on any old Jeep.

cruiser54

Get the throttle butterfly set first. Back the stop screw out til the butterfly is closed. Turn the screw in until the faintest of movement is seen in the butterfly. You're done.
Adjust the TPS using these instructions.


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: 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 a three-wire TPS mounted on the throttle body. This manual transmission vehicle TPS provides data input to the ECU. The manual transmission TPS 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. Adjust the TPS until you
have achieved this percentage. If you can't achieve the correct output voltage replace the TPS and start over.
AUTOMATIC TRANSMISSION: RENIX automatic transmission equipped XJs has 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—
FOR 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. 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.
If you have TRANSMISSION issues check the four-wire connector side of the TPS.
If you have ENGINE issues check the 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 04-08-2012

DESERTXJ206

Cruiser I thi nk my votages were 4.55 and 5.53 iirc. The 4.55 may be slightly higher or lower I can't remember. But I also read you want from. 825-.835 but. 830 was optimal??

DESERTXJ206

Also I think the previous owner may have damaged the screw so bad I may not be able to do those little adjustments. I saw a guy pn YouTube have my same problem and his screw was damaged so he lightly bent the throttle stop plate till it would be almost completely closed. What would you recommend?

Gee oh Dee

Get a new screw or find a good TB for sale?

DESERTXJ206

I was thinking about the new used TB idea. I'll ccgheck m local Amc 4x4 yard today.

DESERTXJ206

My jeep yard says $35 for a used TB. I think I'm going to play with mine a bit and see where it takes me. I'm tired of just throwing sensors at it.