Renix 87, AW4, 4.0, shudder, torque Conv. Lock, engine miss under low rpm load

First a little recent history. I have had this beast for 7 years now, and I have put 60,000 miles on it in that time (now at 280,000). I swapped out the AW4 recently, and the TC. I had a small exhaust leak at the flange-donut, got it fixed by a muffler shop last week (new donut), just after finishing the AW4 swap out. He used a torch to loosen the flange (so ???-O2 sensor, and wires???). Then I got it inspected (Texas emissions) and it passed NOx by just 1 PPM, but it passed. Cat is only 18 months, <10,000 miles old. O2 sensor was good before the AW4 swap.

Old AW4 was slipping badly (internal hydraulic leaks, seals too old and worn, not an electrical, TCU problem). The swaped AW4 seems to work fine, but!

Before I did the AW4 swap, I was starting to notice a little pinging at WOT, in 3rd on the freeway. ( I do not have a knock sensor, but the pinging was new, recent problem, last days before the AW4 finally died).

Now, in Park, from start up the engine runs fine, 650-4000 RPM runs fine, but warmed up idle has fallen to about 450 to 500 rpm, for some unknown reason. In drive with AC on the Idle is about 700 rpm!

I test drove it at 0-35 MPH around the neighborhood, and it was fine the first 35 miles. I test drove it first with the TCU disconnected for 2-3 miles, then went to electronic operation in Drive with the TCU connected the last 32 miles, and it seemed fine. The I took it on the freeway today after 35 miles of local low speed testing around the neighborhood, but....

Trying to get up to speed today I got a nasty shudder, like engine was bogging down, but no pinging. The MPH dash, gauge needle was bouncing +/- 2-3 MPH, no long smooth climb like before. Also the TC was always locked up when it bogged down. I know, because I have a custom power switch override, and TC locked indicator lamp, that I installed a few years back that allows me to disable TC lock up, and allows me to see when the TCU sends power to the 3rd solenoid to lock up the TC. So if I see the light come on and the RPM drops about 250 rpm, I know it locked up the TC.

I went ahead and took a 30 mile freeway, each way, test drive tonight, and discovered that if turn off the TC lock up switch and drive in 3rd gear at 45-65 mph (around 2600 to 3000 rpm), the jeep drives fine, no shudder, decent acceleration for an old tired engine, but with the TC locked up at about 35 MPH (2000 rpm or less) it is a little like riding a bucking horse (but a very much milder shudder, than a horse, LOL) at WOT and takes forever to get up to speed, and it does not down shift like it should at WOT, and the MPH needle bounces +/- 2-3 MPH.

Gas mileage since I started these tests (since I finished the AW4 swap), has been about 1/2 of what it use to be.

This may not be a single problem. I need to make list of things to check, and test. Any ideas folks??????

Besides asking the wrong person, I have never bought an automatic anything for myself since 76 and other than the 97 grand that I bought knowing the 727 and rear D35 was bad have no intentions of ever buying a auto again cept for the wife, autos are the devils spawn...
But to me, sounds like the auto tranny you swapped in has problems but first I would go over every ground you can find anywhere near where he was welding.

The other thing, if he was using an arc welding and attached his ground to the tranny I don't think thats a good thing. I have a few automotive friends/customers that we finally figured out they needed to turn off their wireless access points when they welded, arc welding screwed them up big time.

You have tested the O2 sensor recently or not?
Perhaps the knock sensor has failed.
Is this the torque converter that came with the used AW4 or your old one?

Welding on a Renix does not damage the ECU.

He did no welding, just heated the flange/pipe/manifold at the flange to get a bolt loose and the old gasket loose. He used a gas torch. There has been no welding on this jeep since I bought it 7+ years ago.

I used the TC that came with the known working AW4 I bought as a spare and stored on the shelf in 2006-07, apx.

Cruiser54, re-read my post. I have never had a working or connected knock sensor on this jeep since I bought it, and this problem is NEW!

All sensors were pretty new (less than 5 years, less than 60,000 miles), except the coolant temp sensor in the block, and all were frequently tested and working properly just before I swapped the AW4 and TC.

I have not tested anything except the drive-ability, since I swapped the AW4 and TC. Keep in mind it did pass a tail sniff, 2 speed emissions tests just last week, before I took it on the highway.

Also keep in mind that I can lock the TC in third gear at about 45 mph and goose it to near 70 mph with out the shudder, or the wobbly MPH needle, as long as I am in the 2500 to higher engine rpm range (but it does not down shift if I do it in drive, over 35 mphs).

Checking the O2 sensor wiring, and sensor is on the top of my list, as well as confirming the TPS ground, and idle to WOT data on the TCU and ECU sides.

I might add, that now that the small donut leak on the flange at the manifold to down pipe is closed (new donut) the engine is running at a lower rpm in park only, about 450 to 500, versus 700 rpm previously, and it sounds like a deep tuned exhaust like an off road racer now, which is a little odd. BUt that leak was very close to the O2 sensor, and should now be gone!!!!!!

Now I did re-calibrate the throttle body down and later back up near factory settings in prior years when I was chasing the high idle gremlins, so with the exhaust leak fixed, I may need to adjust the idle stop screw again on the throttle body one last time, and the screw on the side of the throttle body in particular, and then recalibrate the TPS, but only after I verify the O2 sensor and wiring was not buggered up by the clown at the muffler shop, and I doubt that is the problem here, except maybe for the low idle, but the IAC should be boosting the idle in spite of that, so I may be back to the O2 sensor and wires. I will definitely check for flame damage of any sensors or wiring near the donut!

A screwed up O2 signal might explain the current issues, and might be consistant with the poor power, but it acts like it is late on the timing (spark) during acceleration as well.

But I am looking for a complete check list here, and ideas of what to check (like have I changed the air filer in the last 3 years?, hmm, LOL, I doubt that is the issue this time as it is the low rpm range, shudder with locked TC, where I am having trouble, not at 3000 rpm where more air is sucked in).

Aslo, IIRC, when in 4th, then when goosed at WOT it should drop to 3rd, and from 3rd to second when goosed from cruise to WOT while in 3rd, and as I recall the TC light I have, use to show me an unlock and relock step as it down shifted, but the light is staying on and I am not getting the down shit if I am over 35 mphs.

The transmission works fine with the TCU disconnected, but that also disables the TC lock up. Since the TC lock up works fine at 3000 rpm, I am suspecting Renix engine management issues mostly. And the TC lock unlock issue I guess could be a TPS/wiring issue, which is once again a renix sensor/wiring issue.

I am wondering about the MPH gauge needle bouncing at 2000 rpm area during the shudder, as I think it sends data to the ECU and or TCU about vehicle speed, VSS? But it only does the needle bounce, and speed shudder, at WOT, around 30-35 mph, when I floor it, and when the TC is already locked up, and as I said the TC is not unlocking and down shifting the AW4 like it should when I floor it.

Thanks and please keep the feed back coming!

When you replaced the trans, did it have all the wiring on it up to near the trans dipstick?
What I'm getting at is there may be an issue with the black and the gray connectors located there.

cruiser54 said:

When you replaced the trans, did it have all the wiring on it up to near the trans dipstick?
What I'm getting at is there may be an issue with the black and the gray connectors located there.

Click to expand...

Yes all the wiring there is fine, two main pairs of conectors. In fact I fixed the lost back up lights as one pin on the jeep side of one of those 2 connectors was bent flat, sideways, by the prior mechanic that I had swap out my NSS about 6 years ago (one of many errors of his I found and fixed myself over time). I took great care in making sure both pairs of connectors were clean enough to eat off of, and that they went back together with no screw ups, dirt or binding or bent pins. I was a bit surprised at how clean, and new looking the guts of those old connectors were!!!!!!!!!!! Those weather packs are great!!!

Also took great care in cleaning, inspecting and reinstalling all the cables and sensors on the transmission, off the top of my head, the VSS/ speedometer cable, the NSS, the cable that sets fluid pressure (I forget it's name, goes from the valve body to the throttle body).

The more I think about, I had it up to 50 mph, before I took it to the muffler shop, with out today's problem (not sure if I recall this accurately, but seems like I would have done that before the emission inspection..etc), so I am thinking he screwed something up something near the O2 sensor. He did spray wd-40 (or equal) on the bolt near the O2 sensor, before he used the torch. But they should know what to use that is O2 sensor safe.

I did forget to mention that I installed I brand spanking new (from Rock auto), NSS switch on the transmission!!! It looked so perrrdy! LOL

IIRC the new NSS was one of the two connectors you asked about.

Yep, that's one of the connectors, the NSS. Have you looked to see if he accidentally melted the harness to the O2 and/or CTS sensors?

All V test data is Engine off power on data, and Ohms data was with power OFF:

TCU side of TPS:

4.67 V TCU input to TPS on TCU side, versus firewall ground
3.9 V out, at Idle
1.28 V out at WOT (I think this is too high? (1))
TPS to firewall ground .5 ohms! (power off test!, Note I get bad readings on ohms with power on)

The power off ohms test of the TCU side of the TPS seemed odd, span seemed too small (1), so I did power on V tests. I need to go back and check the isolated and connected resistances and compare to those in my old "RenX Files" thread data, but I am suspected the TPS is part of the problem.

-----------------
ECU side of TPS:
4.87 V in to firewall ground
.756 V at idle
3.35 V at WOT
.5 ohms TPS to firewall Ground (power off)
-------------------------------

Sure enough, it looks like I have another bad TPS on the TCU side!

I will recheck it, but IIRC I was only getting about 4.2 to 2.4 ohms, mounted.

http://www.naxja.org/forum/showpost.php?p=244960875&postcount=240

It drove fine initially but when it warmed up after a few minutes of driving, the tranny would no longer shift out of first (and the idle was running high). I did a little research on here that led me to suspect the TPS may be bad.

I measured the impedance on my TPS (warm) and got these readings:

TCU Side:
Pin A to B: ~6.6k (idle) to ~2.4k ohms (WOT)
Pin A to D: ~200 ohms, constant
Pin B to D: ~6.5k (idle) to ~2.3k ohms (WOT)
ECU side:
Pin A to B: ~47 ohms, constant
Pin A to C: ~2.4k (idle) to ~3.6k (mid) to ~2.4k ohms (WOT)
Pin B to C: ~2.4k (idle) to ~6.3k ohms (WOT)

It appeared I had some internal shorting and other issues, but the readings were erratic as well. This pretty much convinced me the TPS was faulty, so I decided to replace it. I bought an Echlin one from Napa for $45. Before I installed it, I decided to check its impedance to see how a new one compared. I measured:

TCU Side:
Pin A to B: open circuit, constant
Pin A to D: open circuit, constant
Pin B to D: open circuit, constant
ECU side:
Pin A to B: ~4.0k ohms, constant
Pin A to C: ~6.3k (idle) to ~2.4k ohms (WOT)
Pin B to C: ~2.3k (idle) to ~6.4k ohms (WOT)

It seemed odd to me that the TCU side measured open between its pins and a little further looking on this forum led me to this thread and Ecomike’s measurements showing the TCU side was a second reverse pot. I returned the first TPS to NAPA and got a replacement. The second unit measured:

TCU Side:
Pin A to B: ~2.4k (idle) to ~6.5k ohms (WOT)
Pin A to D: ~4.1k ohms, constant
Pin B to D: ~6.5k (idle) to ~2.4k ohms (WOT)
ECU side:
Pin A to B: ~4.0k ohms, constant
Pin A to C: ~6.3k (idle) to ~2.4k ohms (WOT)
Pin B to C: ~2.3k (idle) to ~6.4k ohms (WOT)

All seemed right with this one. Goes to show that you probably need to check a new sensor before installing it. I have a habit of checking parts most times anyways (brake cylinders, starters, alternators, etc.) before installing them on a vehicle to save possible headaches later.

I installed the new TPS. I also checked the ground wires for the ECU and TCU and found them to be floating up to nearly 0.7V. I added a temporary ground wire over to the battery negative terminal and the idle sounded a bit better, so I took it for a test drive. All tranny gears had returned. It shifted and drove fine.

Power off, TCU side of TPS, probing the TPS wire sides, I get 3.68 ohms at idle, and 3.16 ohms at WOT, so the TPS is absolutely toast on the TCU side of the sensor!!!!

I bought this TPS only 4-5 years ago, and doubt it has over 45,000 miles on it!!!! I believe it came from AZ.

I am about to loose it folks, and murder some Jeep gremlins!!!!!:flame:

OK, back the battle front. Replaced the TPS, no joy. The old TPS, it seems was OK afterall.

So going back to post number one, add the TPS is new and calibrated, and I got no change in performance. Still a miss at idle in park, not bad, but there. Idle is still about 200 rpm lower than it was with the exhaust flange donut leak. No miss at 3000 rpm in drive with TC locked. Which I think eliminates many possible ignition problems as the cause??. Bad HV wires, coils, etc usually act worse at higher rpm I think. The problem is high loads at low rpm. Also noteworthy, is it was pinging under WOT before the AW4 swap, if it did not down shift first (like from 4th to 3rd), but now it shudders, and does not ping (does not knock) at WOT, with the TC locked up. With the TC disabled it down shifts, and does not shudder, and does not ping!!!! I DO NOT have a knock (ping) sensor on this jeep!!!!

At 2000 rpm, or lower, with the TC locked it shudders with a miss and stumbles a little, if I try to accelerate at all, not real bad, but bad enough to be very obvious. The stumble is worse if I accelerate, and TC will not unlock when I accelerate,, so I now suspect a brake switch, TCU, ground fault, and possible overlaping ignition issue (plug, wire, distributor cap, rotor....?) and even an exhaust issue, as I have a loose muffler rattle, probably just a loose hanger we failed to tie down, but unknown for now exactly what may have been added to the gremlin list.

One last note. I was at 35 mph, in 3rd, shifted to 1-2 (and got 2nd), and the TC stayed locked, and stayed locked until it hit 1200 rpm, even if I had my foot on the brake!!!!! This is why I suspect a TCU-brake switch, wire, or ground problem of some sort!!! I have worked on the brake switches before, and guess I need to verify the TCU itself is grounded (had it on and off the mounting area previously). Since the solenoids are working, I think the AW4 ground is OK?

Didn't read everything but it sounds like your switch on the brake pedal isn't telling the TCU to unlock the TC.

old_man said:

Didn't read everything but it sounds like your switch on the brake pedal isn't telling the TCU to unlock the TC.

Click to expand...

Thanks. That is what I am thinking too. Especially after my last test drive results. IIRC the switch removes the power signal to the TCU and grounds the leg to remove any residual voltage (capacitance). So I think I need to check grounding too. IIRC I noticed a .2 volt reading on that line in the off position about 2 years ago, but it was not causing a problem at the time.

Do you know if the TC is suppose to unlock immediately when the brake is applied?

to the best of my knowledge, yes it should. That is one test to determine if it's working-- constant 55mph and tap the brake should give you a 150-200rpm increase when it unlocks.

Shorty said:

to the best of my knowledge, yes it should. That is one test to determine if it's working-- constant 55mph and tap the brake should give you a 150-200rpm increase when it unlocks.

Click to expand...

Mine seems to be a good 300 rpm change between locked and unlocked at higher speeds (about 50 mph) and rpms (3000 rpm in 3rd). I used my over ride toggle switch I installed about 3 years ago to test it today.

As I recall it use to unlock almost instantly before I did the AW4 swap, so I will dig into there later today when it cools off.

The second pair of wires on the lower brake switch (this one has cruise control, with an upper switch), had a broken wire. I fixed it, but it changed nothing.

???

I cleaned the inside of the cap and rotor, both were covered with a fine layer of copper/zinc oxide (brass) dust. The engine runs better, about a 35 to 50% improvement. O2 sensor data seems pretty normal, tested good.

I ran a vacuum gauge test, and the engine vacuum is great, no sign of low compression or burned valves, or vacuum leaks, so I will check and clean the spark plugs next!!!!!!!

Still have a major ground or related issue on the TC lock up it seems. Still is not unlocking when I hit the brakes!!!!!

Cruise54, are you sure the upper brake switch is not the one that signals the TC to lock, or unlock when cruise is installed?

My brake lights work (so I know the brake switch, lower one, works) and has worked, as it just passed safety inspection a week ago.

No, I'm not sure. But, AMC always used the other terminals for cruise control. I'll bet the brake switch signals the TCU whether or not the vehicle is equpped with cruise.

Well interesting events on this since my last post. I fixed the broken wire on the brake switch, wire 4 of three (dual wire set on the bottom switch, it also has a cruise switch up higher), but it did not seem to solve the problem.

Then I checked the Cap and Rotor, and their was a fine dust, brass oxide, all over the inside (HV short?), so I cleaned it and sanded the tips flat, and it ran (the engine) a whole lot better, but the TC still did not unlock and the AW4 did not down shift at WOT over 30 MPH like it should. I parked it for two weeks, and I guess it decided I was pissed and now it works!!! LOL

:clap:

Had this beast since 2004-05 or so, and this is the first time I finally felt the 4.0 and AW4 all working properly with real power!!! Seems I am no longer
hasta

arty:TIME!!!!

What is interesting is that with my TC lockup LED light, I can see it unlock and relock in just about 0.5 seconds (FAST!!!) as it shifts down to the lower gear when I floor it. Also I can for the first time cruise at 35 mph in 4th gear, at 1200 RPM, if I get to 40 mph first, get into 4th, and then just let it slow down to 35 mph and cruise!!! No bucking, or shudder now!!!

Lastly, it does not unlock the TC when I apply the brake, it waits until vehicle speed hits 25 mph, and 1200 rpm, and then unlocks the TC, and the engine rpm drops to 750 rpm right away, but it runs smoothly slowing down or speeding up slowly or at WOT now!

No doubt I still have a sleepy gremlin lurking (I think?) but for now it is most promising to have this 87 Waggy acting like new again!

Update: On my 87, I changed the plugs, rotor, cap and air filter in my 87. Found a funky electrical connection on one injector, this week, took it for a test drive today. One interesting note, it was driven the last 18 months or so with two different single platinum tip brands of spark plugs. 2 were Autolite and 4 were Bosch. The Bosch still looked brand new-clean, the Autolites had some carbon fouling, they were on the front two cylinders. The Cap and rotor were on their last legs, wires were still good, not very old yet. Idle has dropped from 750 to 550 for as yet unknown reasons.

Mike-you mention the metallic dust under the distributor cap. Did you by chance try to wiggle the shaft? I noticed the same thing earlier this year with my '96, at a little under 160k miles. The shaft was loose in the body of the dist., and the rotor was tearing into the contacts in the cap. Both had been done at 150k. I replaced it with a rebuilt, and so far, so good!

I wish I had knowledge of RENIX, but alas, our oldest is a '92. But, the problems you're having sound exactly like the same demons I was fighting in my '96. When the trouble started, though, I had the luxury (?) of having the CEL tell me that the TPS was on its way out. I was climbing a rather steep hill on I-81, at 65MPH, and the HEEP skipped a beat, but kept running fine. I finished my errands, returned home, and read the code. Over the next 15 months, I went through a new one-a Standard brand, and four used ones out of the JY. They all exhibited different symptoms, like stalling at red lights, idling nicely then trying to pull through a red light, stalling or racing while driving along, or the tranny shifting erratically while cruising along or at speed on the interstate, with the TC dropping in and out of lockup. The various TPS's would behave OK at first, but over the next few weeks or months, would start mis-behaving. The one that's in it now was, ironically, the oldest one, with its donor car having the most miles.

Somehow, I think the TPS may be the root of your problems.