97 JGC stalling - torque converter?

[kat75]

1997 JGC 4.0L. Have had problems with transmission slipping/engine stalling. I'll start at the beginning.

We would have trouble on long trips after being on the road a couple of hours (interstate, 65+mph). The engine would not stall, but we would lose power--the transmission would still be in drive but you could floor the accelerator and NOTHING would happen, tach stayed same. The first time it happened we were less than 1/4 tank on gas and thought that might have been the problem. Also seemed to help to pull off, turn off the engine, and let the car sit for 5-10 min. When this would happen, we checked transmission fluid and it was bubbly. Thought maybe the kooks at Wally World overfilled it because there was some splashed around as well. (btw--father-in-law thinks he's found the problem, we thought there might be air coming in somewhere and he found a pinhole in one hose.)

Okay, hubby and dad-in-law changed trans fluid and found some (not a lot) of flakes on the magnet. Fluid was brownish but not burned-smelling (just smelled like transmission fluid.) Didnt have a problem with the car for a good while, but we didnt take many long trips, either.

Now it's gotten a lot worse. Last night we were on our way back from family's house and was only on the interstate 15 min and it got real bad (it's started lurching and sputtering as well, and the engine cuts out.) We had to stop 2 or 3 times. After we got halfway, we get off interstate and it's 45-55 mph with stoplights the rest of the way home, and didnt have any more trouble. Hubby drives it to work, it's about 25 miles at 45-55 mph with stoplights and never has trouble with it. We never have any trouble except on long trips at high speeds. It also seems to be worse if we use cruise control and if we go up hills, but not all the time (we took a trip into the mountains, was on the road for probably 3 hours and when we started really getting into the mtns it got really bad.)

Could this be the torque converter? I have read on other posts that the engine cutting out and metal flakes are symptoms that the TC is going bad. Does anyone have any other ideas?

[kat75]

father in law says he doesnt think it's the torque converter. Does anyone else have any ideas?

[Bob D.]

I agree that it doesn't sound like the torque converter. How many miles? More miles - more likely a internal problem.
May want to flush the tranny.

I also wouldn't totally eliminate non trans related problems.

[kat75]

It's got 120,000 miles.
We're just baffled by the fact that while it's still running, driving at 65mph, that suddenly pressing the accelerator does nothing (not stalled yet) and it starts to decelerate since the gas pedal isnt registering. Putting it in neutral sometimes makes it start responding, but sometimes there's nothing we can do but coast to the side of the road and turn it off.

[kat75]

oh--btw, FIL thinks it's a coil. If it was a coil, wouldnt it just lose power, not cut out completely?

[Bob D.]

This is not sounding like a transmission problem.
One symptom - opening the throttle under load and getting no response - sounds like a plugged exhaust, usually the catalytic converter.
Do the rpms stay the same but the motor sounds like its getting bogged down?
Maybe the TPS (throttle position) sensor but I'm just guessing.

[kat75]

Originally Posted by Bob D.

Do the rpms stay the same but the motor sounds like its getting bogged down?

Yeah, I guess you could say that. Going highway speed, suddenly rpms drop (as if I completely took my foot off the accelerator) and get no response pressing the gas pedal. It will pick back up intermittently, but more often no response, so that speed drops back so much I have to pull off to keep from getting run over. Slow speeds, or short trips (no matter what speed) dont have this effect.

[kat75]

Okay, did some research on catalytic converter and TPS, found some posters that had problems similar to mine--could it be a bad O2 sensor, dirty throttle body, plugged catalytic converter (we have an odd metallic rattling noise that seems, after research, to be connected to a bad CC)?

[Bob D.]

Could be any or all of those things - but I would eliminate a possible exhaust restriction first. Any muffler shop should be able to test a restricted exhaust, sometimes for no charge.
Done properly, it requires drilling a small hole and pressurizing the exhaust.
If the cat. is really bad the catalyst material inside will start to disintegrate and the remnants will be loose and can be shaken out.
This could be the source of the rattling.
Just take it one step at a time.

[oljeeptek]

Interesting symptoms. O2 sensor is not likely. Minor metal flakes are not necessarily a cause for concern, but a lot are. If the fluid is still bubbling, its either overfilled or overheating. A slipping lockup clutch in the torque converter could indeed cause the trans fluid to overheat. Try driving around with out overdrive and see it it goes away.

You should be getting some kind of response to throttle changes however. Does a manual down shift change anything?

An electronically shifted trans should be able to provide codes if scanned. (I'm a little rusty on specific applications, sorry.)

Have you checked for any service bulletins?

[oljeeptek]

Oh yea,

Tap the cat with a rubber mallet. If it rattles its bad...

[kat75]

Thanks, Bob & oljeeptek!

Originally Posted by oljeeptek

O2 sensor is not likely.

I wondered about this. It just got inspected recently and passed emissions. I wondered if it was maybe just the one in front that was bad.

Originally Posted by oljeeptek

Minor metal flakes are not necessarily a cause for concern, but a lot are. If the fluid is still bubbling, its either overfilled or overheating. A slipping lockup clutch in the torque converter could indeed cause the trans fluid to overheat. Try driving around with out overdrive and see it it goes away.

Father-in-law did confirm that it was just a few flakes, not big ones, and he didnt think it was anything to be concerned about. I did NOT know that a bad TCC could make the trans fluid overheat!
Hubs said he tried turning off OD but I asked him, did he turn it off BEFORE or AFTER it started messing up, and he said after. I figure that at that point it's a waste of time. We will try turning off OD on our next trip. I thought about that but I'm not a car expert (obviously!) so I didnt try it.

Originally Posted by oljeeptek

You should be getting some kind of response to throttle changes however. Does a manual down shift change anything?

Havent tried downshifting but when the problem first started, shifting into neutral for a few seconds seemed to help. Now that doesnt help at all, since now, it's not only not responding, but shudders and cuts out altogether, whether in N or not.

Originally Posted by oljeeptek

An electronically shifted trans should be able to provide codes if scanned. (I'm a little rusty on specific applications, sorry.)
Have you checked for any service bulletins?

We did check for codes the "manual" way (not with a scanner) back when it first started, and it didnt come up with anything. We'll try that again and see if anything comes up.
Last time I checked the TSB's (a year ago, when we bought it) nothing pertained to our problem or had already been taken care of. I'll check when I get to work this morning and see if there's anything new that's been added.

Thanks again, all!

[kat75]

Originally Posted by kat75

Last time I checked the TSB's (a year ago, when we bought it) nothing pertained to our problem or had already been taken care of. I'll check when I get to work this morning and see if there's anything new that's been added.

This is all I could find that MAY apply to my problem.

REVISION IN DIAG. PROCEDURES AND LABOR TIME FOR RE TRANSMISSIONS
Changes have been made to the diagnostic procedures and associated labor operation times for testing and/or replacement of the Torque Converter Modulated Clutch/Overdrive Solenoids, the Governor Pressure Sensor, and the Governor Pressure Solenoid on all RE transmissions built since 1996.

VEHICLE SPEED CONTROL
SOME VEHICLES MAY EXPERIENCE BUCKING DURING WIDE OPEN THROTTLE (WOT) ACCELERATION.

[oljeeptek]

Originally Posted by kat75

This is all I could find that MAY apply to my problem.

REVISION IN DIAG. PROCEDURES AND LABOR TIME FOR RE TRANSMISSIONS
Changes have been made to the diagnostic procedures and associated labor operation times for testing and/or replacement of the Torque Converter Modulated Clutch/Overdrive Solenoids, the Governor Pressure Sensor, and the Governor Pressure Solenoid on all RE transmissions built since 1996.

VEHICLE SPEED CONTROL
SOME VEHICLES MAY EXPERIENCE BUCKING DURING WIDE OPEN THROTTLE (WOT) ACCELERATION.

I don't think the bulletins are applicable to your condition. The first relates to warranty pay rates, and if your cruise wasn't on, the second is most likely irrelevent.

After rereading all the posts above, I think you're not at a trans problem. (Unless its still foaming over).

It sounds to me like your either losing spark or fuel.

A defective ign coil can mimic running out of gas. So could a crankshaft sensor. You should also have the fuel pressure and volume checked. Fuel starvation would sometimes feel like pushing the gas is as beneficial as stepping on a marshmallow.

Does the vehicle have a tachometer? does it drop way down at the time?

I think you are at the point where some diagnostic equipment is needed. You are going to need at a minimum a fuel pressure guage and a timing light that can be taped to the windshield and monitored on the road.

If it acts up, you can narrow it down easier.

[kat75]

Originally Posted by oljeeptek

It sounds to me like your either losing spark or fuel.

A defective ign coil can mimic running out of gas. So could a crankshaft sensor. You should also have the fuel pressure and volume checked. Fuel starvation would sometimes feel like pushing the gas is as beneficial as stepping on a marshmallow.

Does the vehicle have a tachometer? does it drop way down at the time?

Father-in-law said earlier he thought it was the coil, as well (I wasnt as sure but now I have two Yea votes.) Today on the way home from work, the Jeep left hubby on the side of the road and he had to get a tow home. He said it was doing the same thing (accelerator wouldnt do anything, rpms drop to ~2000, still rolling but no response from gas pedal.) He said that it kept choking out on him. When he got off the road, when he would get it to crank, it seemed to run fine for a minute, and the tach would drop and drop til it cut out.

Originally Posted by oljeeptek

I think you're not at a trans problem. (Unless its still foaming over).

It IS still foaming over, but we'll see how that goes. Like I said before, my father-in-law found a tiny hole in one of the hoses, so maybe that's pulling air. I hope.

FIL's coming tomorrow A.M. to replace the coil...we'll see if that works.
I hope so! I do appreciate all your help.