please help me with my comanche

[1BADMJ]

i have a 1988 jeep comanche with a 4.0. The motor has been running good ever since i put it in. but a few months back it started to idle high when i would start it. iit would rev to 3000 and then drop back down. now it doesnt drop so i have to pop the hood and unplug the tps and then plug it back up. so....i replaced the tps and she started up and ran smooth so i thought i fixed it. the next day when i started it it reved up again.

 

and anther thing.... when i first start my jeep i can drive around town fine but as soonas it warms upi have to BABY it 1st to 4th to get moving then i can cruise back hme. or to the gas station get some food and gas, start it back up and itdrivesgreat. then it warms back up and starts spark knocking and sputtering and it pretty much falls on its face.

 

any help would be greatly appreciated. thanks!

[smuth]

is the TPS properly adjusted? IIRC they aren't just plug and play on the Renix system

[cruiser54]

Pay particluar attention to the "important note".

 

 

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.

If you see more than 1 ohm of resistance 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 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--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 11-28-2011

[Comanchero87]

:hijack:

I have the same problem when she heats up she runs like a dog....popping and loss of power under load. I don't have the high idle problem. I have adjusted my TPS but did not clean the TB before hand though. If you fix your problem make sure to post the problem and solution if possible. I have burnt harness wires @ the knock sensor and o2 sensor so am going to replace these connections and sensors. Ive been told that the renix runs in a different mode when it heats up and all the sensors come into play in this mode. So if I fix my problem I will let you know.

[cruiser54]

Which side of theTPS did you use for your adjustment? Engine or trans? If you use the trans side for diagnostics/adjustment and the engine side of the TPS is wonky, you're working with false info.

[ejndssn]

may also want to look at the egr valve on the port side of the engine :doh: driver's side i had that issue in the past and replaced that unit and all was good and back to normal.

[Comanchero87]

If the EGR is gone won't the diaphragm not be able to move freely? Or am I mixing up the EGR with something else?

[Comanchero87]

C101 cleaning/Ground harness mod/ adjusting TPS, solved the problem for me. No more high idle when it gets hot, no popping through the intake. For the people searching in the future.

[cruiser54]

Correct. Checking and rectifying the sensor ground as needed and outlined in the TPS instructions, along with adjusting the TPS makes a world of difference. The C101 cleaning can cure alot of ills by itself. These are stones not to be left unturned in the diagnostic process.