'93 Lumina -- *sudden* jerking @ ~ 45mph, *please* help

[mickeym]

Allright, this is the background.
1993 chevy lumina (v6) has 155,000 miles and has *never* had the transmission fluid replaced;
well, we dropped the pan and replaced the filter, and therefore refilled it with as many quarts as came out. The fluid is now red, but i've read that you *don't* change the fluid since the dirty fluid is keeping it alive.

I dont know whether this has anything to do with it, but after the fluid has been changed, ~ 10 days later, the car shifts fine and all, but i'f i'm just trying to keep the speed steady at around 30mph, or 42mph, the car will start jerking back and forth, and the 'Service engine soon' light comes on, but goes away sometimes. If i accelerate a bit, it will function normaly, but just 'cruising' at the speed causes the problem.

My guess is the tranny since the fluid was just replaced for the first time. What do you guys think the problem may be?

I've read sensors or what not, i was thinking about taking it into autozone but dont know if codes can be read for a 93 chevy apv.

Thanks for any suggestions; i dont want to lose this vehicle.

[jeffcoslacker]

I think the timing is coincedental. What you are describing sounds like classic torque convertor lockup malfunction.

The TCC locks the convertor (like a clutch in an automatic) solid, so there is no slip, once the car has begun cruising at light load on flat road. The speed you indicated is pretty typical of TCC operation threshold, the jerking is called TCC shudder.

What happens is the electric solenoid that causes pressure to be applied to lock up the convertor goes bad, and starts chattering, making the TC go in and out of lockup rapidly.

It's not a huge repair, but you probably should let a shop do it, as you will probably have to drop the transmission down on one side to replace it. It is under the "pan" on the driver's side of the tranny.

I think it runs around $300 or so for a shop to do it. Not sure. It's been a while since I did one at the shop I worked at, or heard anyone say what they paid to have it done, so don't be mad if I'm wrong.

Good luck!

[jeffcoslacker]

If possible, avoid driving it over 30 mph, or try using D3 instead of overdrive, if you have the OD tranny, until you get it looked at. That rapid lock/unlock is hard on the convertor and the rest of the driveline.

Keeping it one gear lower and preventing it from going into overdrive should keep the ECM from commanding lockup (I think)

[jeffcoslacker]

P.S.

There are a couple of ways to disable the TCC so it doesn't do that, I can coach you if you want to try it. That will verify that it is actually the problem, but will make the check engine light be on constantly, and will really eat into your fuel mileage, so you don't wanna drive around like that for long.

[mickeym]

Damn, this might be since we replaced the fluid -- i told him not to do it and he did it anyways...

What do you guys recommend, should i take it in to read the codes?
Yea, its probably the torque converter, since it happens at around those speeds, as shifting is fine.

Which part is it again? And the *whole* trans needs to be dropped to replace this?

How long do you think its 'driveable' if we just let this happen?
Do you think that resetting the computer might fix it? Since we replaced the fluid, maybe it needs to be 'retrained'?

Thanks for your suggestions!


(Is it difficult to disable the TCC and enable it to check if that's the problem?)

[jeffcoslacker]

I doubt it's from the fluid change. The part is electrical, and they just go bad. Most of them went out long before yours, like 70-90K miles, so you're doing all right.

Get the code read. If it relates to TCC operation, then that nails it.

Torque convertor control solenoid, is the part we're talking about. Resetting the ECM isn't gonna change anything.

If you look at your tranny, there is an upright pan cover on the driver's side. That has to come off to replace it. Most of them you can't work on it without dropping the driver's side mount, and let the engine/trans lean down to give more access. You have to be able to support it, or things will break.

Check your owner's manual, under the fusebox section, and see if there is a fuse dedicated to the TCC. I think it will say TCC or Lockup. If there isn't anything else critical on that circuit, you can pull the fuse and that'll disable it.

If that won't work, look under the hood at the trans case. On the driver's side, there may be a 4-pin square connector going into the case, with the wires arranged like

OO
OO

disconnecting this one from the case will disable the TCC as well. Remember, you'll get lousy mileage and have a check engine light on constantly with it disabled.

I don't think you can really hurt it driving it disabled, but you will get lousy mileage.

Driving with it jumping will eventually wear out the lockup's hydraulic components or ruin the convertor itself, so I don't reccomend pushing your luck, especially with the mileage you've got.

[mickeym]

jeffcoslacker, i appreciate the effort you've put into helping out.

In addition to the problem, i forgot to mention that the car will 'turn off' when stopped, such as at a red light, but only when the fluid or car is at operating temperature, i.e when driven for ~ 20 or so minutes.
Does this change anything, or is it still most likely the TCC?

THanks

[cadgear]

Does the car die like you let out a clutch too fast? That might be the TCC locking up, hence making a direct connect through the driveline. Your foot on the brake of course prevents the car from moving, so it has nowhere to transfer power to, bang, stalled engine.

Try putting the car in neutral at lights and other stops, see if that keeps it running. As Jeff said, I wouldn't just ignore this by any means, but its not a walk in the park to replace by the home mechanic either.

[jeffcoslacker]

Originally Posted by mickeym

jeffcoslacker, i appreciate the effort you've put into helping out.

In addition to the problem, i forgot to mention that the car will 'turn off' when stopped, such as at a red light, but only when the fluid or car is at operating temperature, i.e when driven for ~ 20 or so minutes.
Does this change anything, or is it still most likely the TCC?

THanks

Like Cad said, that too is symptomatic of TCC trouble. That is the TCC failing to unlock as you come to a stop. That is no doubt what your problem is. I was gonna say that yesterday, but since you didn't mention it, I didn't want to confuse the issue with things that weren't happening, because that doesn't always happen. But when you've got both symptoms at the same time, there is no doubt what the problem is.

The TCC is disabled until the engine is at full operating temp, that's why it doesn't do it when the motor is cold.

[Marlamar]

Hmmm..Jeffco..thats comment you made about the TCC not operating until the engine is up to operating temp explains a great deal about the TCC shudder occurence in my 95-3.1. I had the exhaust manifold and a thermostat installed/changed in my 95-3.1 and shortly thereafter, the TCC shudder began occurring . Prior to the thermostat change (I don't think there was one in it before) , the engine would take a great while to warm up , ..and I never experienced the TCC shudder ...until after I had a mechanic install a new thermostat. now..It happens with regularity after I drive the car around 10 miles (the temp guage reads slightly more than 1/2 scale or normal, sometimes read 3/4 to high if A/C running and climbing hill) i bought a new TCC solenoid but have not tackled installing it..I have the 4t60E tranny and cannot see the 'pan's location you spoke of on the drivers side next to the firewall, guess I'll have to put it on ramps and take a look again.. Oh by the way, my transmission has 1st. 2nd. drive and Overdrive position on gear selector but I cannot get it to go into 1st position..like its stuck or frozen, please comment on these probs. thanks

[decollect]

[quote=

I don't think you can really hurt it driving it disabled, but you will get lousy mileage. .[/QUOTE]

Agreed, Jeffco. My '90 was bought with 256k on it with the TCC already disco'd because it had faulted long ago. I really didn't notice it since it was a 2.5 and I was more interested in just getting cheap transpo, quick. However some 55k+ miles later, some with 750 mile trips and no problems with tranny. Yeah gas mileage was down a bit for a 4 banger but was an improvement over what I had been driving so I wasn't worried too much.
Shouldn't hurt the tranny at all to disengage the TCC

[decollect]

Originally Posted by mickeym

jeffcoslacker, i appreciate the effort you've put into helping out.

In addition to the problem, i forgot to mention that the car will 'turn off' when stopped, such as at a red light, but only when the fluid or car is at operating temperature, i.e when driven for ~ 20 or so minutes.
Does this change anything, or is it still most likely the TCC?

THanks

That nails it then, it IS the TCC. What happens is the torque converter stays in "lock-up" all the way down to idle. That's bad. Since it's a direct lock-up it stalls the engine same as if you forgot to depress the clutch on a manual. And, same as the manual, when you start it up and drop it into gear it will stall if it stays in "lock-up" after the restart.

[jeffcoslacker]

Originally Posted by Marlamar

Hmmm..Jeffco..thats comment you made about the TCC not operating until the engine is up to operating temp explains a great deal about the TCC shudder occurence in my 95-3.1. I had the exhaust manifold and a thermostat installed/changed in my 95-3.1 and shortly thereafter, the TCC shudder began occurring . Prior to the thermostat change (I don't think there was one in it before) , the engine would take a great while to warm up , ..and I never experienced the TCC shudder ...until after I had a mechanic install a new thermostat. now..It happens with regularity after I drive the car around 10 miles (the temp guage reads slightly more than 1/2 scale or normal, sometimes read 3/4 to high if A/C running and climbing hill) i bought a new TCC solenoid but have not tackled installing it..I have the 4t60E tranny and cannot see the 'pan's location you spoke of on the drivers side next to the firewall, guess I'll have to put it on ramps and take a look again.. Oh by the way, my transmission has 1st. 2nd. drive and Overdrive position on gear selector but I cannot get it to go into 1st position..like its stuck or frozen, please comment on these probs. thanks

the cover isn't on the firewall side, it's the whole driver's side of the tranny. It has a cover very much like the pan on the bottom of the unit, with 15 or more bolts holding it on. The TCC solenoid is in there. There is probably not enough room to work through there with the tranny in it's normal position.

The deal with the shifter could just be the way the shift cable is indexed, there is (I believe) a simple locknut type adjustment with a sloppy hole on the cable end or the linkage under the hood. Watch which way it moves when you put it in the lowest selection, and move the cable to allow more travel. Then make sure it still engages park firmly and the pawl catches easily, so it doesn't roll away on you.

[mickeym]

Some more (bad) news...

Two days ago, we drove it, without the above problem occuring, or rather, it may have occured maybe once, i'm not sure.
But anyways, as we're just a half block away from our driveway, the car 'stalls' and cannot be turned on - so we push it to our driveway.
The battery is ok, the engine turns when we try to start it, but it won't turn on.
I'm thinking maybe a fuel pump or something? So to see if it's the fuel pump, is it a good idea to put some fuel in the carburator and see if it turns on?
Also, since this just occured, could the 'stuttering' problem that occured at ~ 30 and ~40 mph been caused by a faulty fuel pump, or does it still point to a faulty TCC?

Thanks for any additional help/info; it'll be greatly appreciated!

[mickeym]

We changed the fuel injector, but the fuel comes to the fuel injector (so the fuel pump sounds like it's not the problem) but then, the fluid fails to go from the fuel injector. We poured gas directly into the carburator and it starts up; otherwise now it just turns.

I talked to a shop, and they said ~ 7 hrs labor for replacing the torque converter, and that's $500 for it.

Do you guys think its worth investing more $$ into the 3.1L APV Van? It has 156,000.

Thanks