DFlintstone

Pete, I think he didn't do #2 cause he has no C-101 connector!

I wonder if it backfired out the exhaust, or back out the intake....

cruiser54

I didn't suggest #2. Only 1,3,4, and 5. Not done? All bets are off.

idahomike

Still working the tips! Working on TPS is next. But I work about 60 hours a week, and don't have a lot of time during the week to try to figure out what is going on with the Cherokee. So to be honest, yep, I am looking for help.

Just didn't see anything that looked like it might make the transmission kick up and down gears. Thanks!

cruiser54

You're seriously missing the point.

Did you read Tip 1?

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

idahomike

With two exceptions, I have completed tips 1, 3, 5 and 7. I have not been able to get to the 10 pin connection behind the drivers side headlight in front of the aircleaner housing. I have the air cleaner housing out and i think I see it. But it is below the headlight housing inside the radiator support, so I haven't Benn able to get my hands on it yet. I also need to add a cable between the neg post and the radiator support. Put a new ground cable between the block and the frame, but not the battery and frame.

As for the backfire, sounded like it came back up through the intake, but I was concentrating more on the transmission acting up, so I'm not positive about the backfire.

I was starting to do tip 6, and check the TPS, last night when I discovered the two screws on the sensor on the throttle body next to the TPS (towards the motor on front of throttle body) were loose. I tightened them up, but haven't had a chance to road test it. Anyone know what that sensor is? Off top of my head I can't remember how many wires it has coming from it - two or three? Could that have been part of the probelm? Thanks, and sorry for spelling this is being sent from my phone.

67 GMC

That's probably the IAC (Idle Air Control) valve next to the TPS. Just screw it back on at this point.

cruiser54

Possibly part of the problem. What were the results on Tip 5?

idahomike

Cruiser54 - I followed tip 5 a couple times. Each time the ohm reading was either 0.0 or 0.01. No fluctuation in reading when wiggled the wiring harness along the valve cover, and along the firewall.

I started tip 6 tonight and had time to expose the splice where the six brown/white wires join together. The factory splice seems secure, but I'm going to cut and soldier the six wires together anyway. Will do that tomorrow - too late tonight.

I tested the TPS: at idle, had 0.65v. Slowly moved throttle to wide open several times and got 4.45v every time. Readings were smooth up and down on analog and digital meters.

Any ideas? Will finish tip six tomorrow night and go for a drive. Thanks again!

cruiser54

Set TPS per my Tips. #8.

idahomike

Cruiser54 Thanks for your help!

Finally had time to complete Tip #8, and hopefully it is working. Cleaned the throttle body butterfly plate - very dirty! Adjusted the TPS as close as I could get. I could get either the three plug wire to the ECU set exactly at 17% of reference output, or the four wire plug to the transmission set exactly at 83% of reference output. But could not get them both to their proper settings.

Three wire plug to ECU: A-B = 4.86 after adjusting (and compromising for four wire plug) B-C = 0.85 (17.5% got to be close enough)

four plug wire to transmission: A-D = 4.66 after adjusting (and compromising for three wire plug) B-D = 3.75 (80.5%). I'm hoping that is close enough.

I took it for a drive an 40 miles later no problem.

Now tips 1, 3-8 are done (exempt for ten pin corrector behind drivers side headlight - cant get it out to clean it. What is it for anyway? Also added extra ground between battery and frame. So far so good!

Thanks again! Mike

cruiser54

Unless working on a shifting problem with the automatic trans, ALWAYS adjust using the flat connector and let the trans values land where they may.

The connector behind the driver's headlight is for the front lighting. They're always grungy.

idahomike

Okay, I was out of town for awhile and couldn't work on the Cherokee. Tips 1 and 3-8 are complete (except for the 10-pin connector behind the drivers side headlight). My daughter took it out yesterday, and Cherokee backfired REALLY loudly and died. It was loud enough, my wife heard it about 1/4 mile away and our neighbor asked my daughter if someone shot at her (she's from California). Not sure if the backfire hurt the muffler, but the muffler does seem louder now. My daughter said it wouldn't start until the 4th try. I worked late, and just had time to start it last night. She also said it wouldn't start for her the day before yesterday after having been parked for 5-6 days. Started right up for me, but I was not able to take it for a drive.

I'll put a timing light on it tonight and see where the timing is. I will also recheck the CPS output (last time 0.4v) and recheck the TPS output (when set last week it was 0.83v or 17% of the reference as per tip #8). Any ideas? Thanks!

*The Dude*

There is a ground strap at the fire wall behind the map sensor that connects to the back of the engine block. They get corroded and cause many issues. Check it to see if it looks questionable.


Also one on the intake that is the ground for the injectors. Make sure it is not corroded up. If you find them questionable, clean or replace them.


Hope this helps. Electrical problems are a PITA.

idahomike

Well guys, kt ended up being the TPS. Even though the old TPS tested good, and was adjusted as per cruiser54's tip #8 there must have been a sporadic short or something. changed the TPS Sunday, and have driven it about 130 miles, with no problems. Still knocking on wood, and keeping fingers crossed, but hopeful! Thanks for all your help!

DFlintstone

And the crowd Cheers! :hea dbang:

Glad you nailed it Mike! (Well, you and post #14!)