Kris503

I own a 1990 Jeep Cherokee Laredo 4.0 Renix. Today I Decided to clean my TB, Before I started it started up fine. After I was done it wouldnt start, all lights, stereo, headlights all worked but it wouldnt turn over, and sounded as if everytime i tried it got weeker and weeker till the lights started flickering when i turned the key. then no response but the lights remained on.. Coould it be my TPS? I dont know

A little history on my jeep, have had to replace rear main seal, fuel pump seems to prime every time i turn the key (since recently I havent heard it priming) A sensor on the bottom of engine is busted, I want to say its the CPS sensor but im not sure. (I was runing with it busted but had rough idle and died on cold start Im not sure if that is part of the issue). My jeep has a push button start, and just put on a new cold air intake today. Also battery and cables are newer and clean, battery charged at 11.80 on my multimeter Key off.

Thats all the info I can think of off the top of my head, Help would be much appriciated.

OleBlue

Sounds like you have a bad connection somewhere. I would check your batt terminals first, second check all you push button start wires.

As for the broken sensor, its probably your knock sensor, the cps is on the top of the bellhousing near the driver side back of the engine.

Also possibly a coolant temp sensor, those are the only two sensors i can think of on the side of the block.

OleBlue

Hmm, also, try putting the jeep in nuetral and then starting it, could be your brake switch or nss.

Kris503

Ok thanks Ill try those, and post back if it works

cruiser54

Knock sensor is right above the oil pan, on the block, on the driver's side. It will cause zero driveability issues.
TPS or any other sensors will not cause slow cranking or draining battery.

It's back to basics as Ole Blue suggests. This is coincidence, not related to throttle body cleaning.

Kris503

I got the jeep to start thanks Ole Blue, and thanks Cruiser54 found some corroded wires, on i think the crown, or a ground for the fuel pump, havent replaced them yet but got it working.

Kris503

Have you run into any idle problems with the renix? My jeep has this problem where on a cold start it runs fine for a couple seconds then idles down, then up and down, acting like its going to die, reaching Zero rpms, studders then rises back up. any ideas what it could be?

cruiser54

Do this first:

Renix Ground Refreshing
The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, and wasted money replacing unnecessary components.
The components grounding at the dipstick tube stud are:
Distributor Sync Sensor, TCU main ground, TCU "Shift Point Logic", Ignition control Module, Injectors, ECU main ground which other engine sensors ground through, Oxygen sensor, Knock Sensor, Cruise Control, and Transmission Sync signal. All extremely important stuff.
The factory was aware of the issues with this ground point and addressed it by suggesting the following:
Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. Scrape any and all paint from the stud’s mounting surface where the wires will attach. Must be clean, shiny and free of any oil, grease, or paint.
Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Reinstall all the wires to the stud and tighten the nut down securely.
While you’re in that general area, locate the battery negative cable which is fastened to the engine block just forward of the dipstick stud. Remove the bolt, scrape the block to bare metal, clean and polish the cable terminal, and reattach securely.
Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for it’s intended use and subject to corrosion and poor connections at each end.
First off, remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Reattach securely.
Remove the other end of the cable from the rear of the head using a 3’4" socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely.
A suggestion regarding the braided cable:
I prefer to add a #4 Gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18" long with a 3/8" lug on each end works great and you can get one at any parts store already made up. Napa has them as part number 781116.
A further improvement to the grounding system can be made using a #4 cable, about 10" long with 3/8" terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. Napa part number 781115.
　
　
If you want to upgrade your grounds and battery cables in general, contact Jon at www.kelleyswip.com. He makes an incredible cable upgrade for a very reasonable price.
　
Revised 11-28-2011

cruiser54

With the engine cold some morning, snug up your intake manifold bolts working from the center out to the ends.

You may have a TPS issue also but do the ground refreshing and intake manifold bolts first. They have to be eliminated as possibilities.

Kris503

Alright thanks that I'll probably refresh those connections tommorow

Kris503

I did the ground refreshing today, did the extra modifications too. Now it doesnt seem to have a idle problem. It idles pretty high but I think it just adjusted really high, it idles around 1500 rpm. With the throttle body cleaning and now the grounds it is very responsive and enjoyable to drive.

Next Project is Fender Flares

I dont like the look and functionality of Bushwackers, Plus the Price!

Im looking for a cheap good looking Fender Flare alternative, Got any ideas?

I've heard of using garden edging, I heard thats not the best

The conveyor Belt idea seems ok but i dont know if it be sturdy

then there is the Azex from homedepot made out of pvc.

I would be cool to do tube fenders, but i dont have the equipment to do so...

has anybody tried these, or know of a better idea?

cruiser54

This should be your highest priority at this point:

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 bodyand 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

Kris503

Ok checking and adjusting the tps will definitly be my next step, i know that hasnt been given any attention, ill look into that after work tommorow

Kris503

I started testing my jeep today, I first checked the sensor ground harness as it says in your post, I got 00.0 on my multimeter, ( which was set on 20v DCV)

Second I did the Reference and got a reading of 4.88

Third I did the Output, My reading was 0.00

( The Tps torx bolts were fully secured in, and it looked like the sensor arm wasnt touching the throttle arm, im not sure if this would give me this reading)

Should i adjust the tps so the tps arm and the throttle arm are touching? will this give me a output reading?

Or does this mean i need to replace the tps?

cruiser54

Sensor ground circuit test needs to be done with teh meter on ohms.

A 0.00 output voltage is not good.