I would atleast give that TPS test a shot, just need a multi meter to test any sensors on a Renix. Your call, hard to judge how bad of shape its in over the internet.

The chevy fired up first try after its usual winter sleep. Drove about 3 miles to fill it up, took 29 gals of fresh fuel. Drove it another 10 miles to get lumber. While waiting my turn to load it died, started right back up, drove back home. About 2 miles from home, getting off freeway it felt like it wanted to die and did a stop signal when stopped. Fired back up and had to give it gas the rest of the way home to keep from stalling. Get back to it a few weeks later it wont start at all unless i put gas right down airhorn. Thought for sure Fuel issue or the ignition module in distributor. It will idle now because I have it turned up to about 900rpms( a rough idle) and off idle no studdering/hesitation, freeway speeds, up to 80 or so, it runs strong. When adjusting after rebuild it would not smooth out. Got a set of plugs next to try, but off idle it purrs. I was not an english major, excuse the long sentence.

Things done so far

dropped tank...looks good new tank of gas
igniton module replaced
new fuel pump
added external inline fuel filter
rebuilt carb
cap n rotor good

 

If you don't do the grounds per Tips 1 and 5, testing most of those sensors is a total waste of time.

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, failed emission tests, and wasted money replacing components unnecessarily.

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.

For those of us with Comanches, it’s very important to remove the driver’s side taillamp assembly to access the ground for the fuel pump. Remove the screw holding the black ground wire. Scrape the paint from the body and corrosion from the wire terminal. Reattach securely.

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 03-04-2013

Cruiser’s Renix Sensor Ground Test


This sensor ground circuit affects the CTS, TPS, IAT, MAP, ECU and diagnostic connector grounds. It’s very important and not something to overlook in diagnosing your Renix Jeep as it is common for the harnesses to have poor crimps causing poor grounds. If any or all of the sensors do not have a good ground, the signal the ECU receives from these sensors is inaccurate.

Set your meter to measure Ohms. Be sure the key is in the OFF position. 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 runs parallel to the valve cover and also near the MAP sensor mounted on the firewall. If you have an 87 or 88 with the C101 connector mounted on the firewall above the brake booster, wiggle it, too.

You want to see as close to 0 ohms of resistance as possible. And when wiggling the harnesses/connectors the resistance value should stay low. If there is a variance in the values when wiggling the wires, you have a poor crimp/connection in the wiring harness or a poor ground at the engine dipstick tube stud.

Refreshing of the dipstick tube connection is covered in Tip #1, and the sensor ground upgrade is covered in Tip #6.

On 87 and 88 models, you could have a poor connection at the C101 connector as well. See Tip #2 and Tip # 27.

Revised 11/01/2014

 

Well the one that is valve cover to drivers side fire wall is not there, the bolt for the firewall is not there even. But all the connections it listed....well they are not good looking

 

Fix them.

 

Got all the grounds replaced that I could find in the engine compartment. Haven't test drove it yet but I'm going to this weekend. If it still does the stupid tranny problem, I'm just gonna swap trannys (it came with a new one when I bought it). I was told by my mechanic that it could also be the shift pump in the trans. So instead of taking the tranny out and replacing the pump I'm just gonna put the new one in and call it good. Hopefully that does the trick. And if not, we'll gonna have to dig deeper. Cruiser54 that wiring guide you posted really helped. And thanks to the rest of you for advice also, I'll keep ya updated