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Tranny/converter slip?


gr8shot

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My fiance was driving the car (96 cutlass supreme 3.1L 211k miles) in Omaha and had to put it to the floor a couple times in traffic. She complained to me that the tranny would slip and shudder before it would downshift. Then it would downshift and go like its supposed to. It has happened to me a couple times too. I can feel a shudder before the downshift. Then once it downshifts its fine usually.

 

After her trip I tried to recreate the problem and did but not every time. I also noticed a surge once downshifted at about 70-80% throttle. I drive the car 95% of the time and honestly don't think I've put it to the floor since I've owned it except this time trying to recreate her problem, so I've never noticed any problems except once in a great while a little shudder if i have to pass a car real quick on the highway.

 

Also after the good flogging, the converter didn't lock for probably 5 miles of highway driving. Then when it finally did it was a very weak lockup and would unlock very easily.

 

The fluid level is fine and doesn't smell burned at all. And I'm not sure of this is the original tranny or not, but I'm assuming it is. Do you guys have any idea what's up? Don't have the funds for a rebuild right now with a wedding coming up in 2 months. Think it will be fine for a while as long as I drive it nice? I drove it to work today and as usual it acted perfectly normal. My drive is about 55 miles one way, 100% highway driving.

 

Thanks for any help!

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not locking on the highway could have been two things IMO:

 

trans temp was too high to allow it, so the ECM disabled TCC lockup

 

or

 

you have this apparently common issue of the TCC apply piston having issues that cause lockup to fail, though normally that causes lockup to work for a while, then as the trans warms, it just fails to lock the converter.

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Sounds to me like the lockup problem was more due to the first problem. After a few miles it did lock up. And today going to work it locked up good and strong just like every other day, and held strong if I'd give it a little throttle but not enough to downshift.

 

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I've had similar issues twice with my LQ1, neither of which were actually the transmission. The first time, a crummy throttle position sensor was sending confusing information to the ECM, causing the transmission to act funny, the second time, a failing coil was causing a fairly noticeable misfire under load. Any possibility that's what's actually happening here?

 

Bump.....

 

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I suppose the tps could be a culprit. When the motor is hot sometimes it dies right away when you start it. It fires and revs to about 1300rpms then just dies. It'll start right back up and run with a touch of the throttle and the idle will smooth out after a couple seconds. Does that sound like something a failing tps would do?

 

I dont think a coil is bad as its not consistent, I'd imagine a bad coil would be noticeable each time you put a good load on the motor, right?

 

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  • 3 weeks later...

Well I'm pretty sure the studder is electronics. I took the car on a trip to Omaha and back on Saturday (125 miles each way) to pick up my 95chevy w/12v cummins project. And the whole way back it would studder and stumble when I'd put a load on the motor. I stopped once and when I'd rev it it would misfire right for the first split second then keep revving. The SES light is on as well. Ill get the codes today and post them.

 

Last night I tested the coils. Im not sure what the right way to test them is, but I went across the two plug wire connections and all 3 were about 7.5k ohms. Is that the right way to test them? I'm going to test them again when I get home today while they're hot and see if anything changes.

 

Saturday when it acted up was the hottest day of the year so far, not sure if that's relative or not. But today it was about 50* and it ran fine on my 60 mile drive to work.

 

Any ideas?

 

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7.5Kohm secondary resistance sounds normal.

 

don't suppose you want to check primary resistance?

 

also, as a quick test, hold up the brake pedal using one foot and apply a normal amount of throttle with the other at ~55MPH... i wonder if you are having the same issue i did back a few years ago.

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7.5Kohm secondary resistance sounds normal.

 

don't suppose you want to check primary resistance?

 

also, as a quick test, hold up the brake pedal using one foot and apply a normal amount of throttle with the other at ~55MPH... i wonder if you are having the same issue i did back a few years ago.

 

How do I test primary resistance? I've got a good multimeter just need to know how to test things correctly.

 

Ill have the codes read shortly too.

 

What am I looking for when I do the brake/throttle test? Just to see if it misses and stumbles a bit?

 

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testing the primaries, you would need to pull each coil pack off, you'll see 2 electrical connections on the bottom side. do an ohm check there. i can't find the spec for primaries at the moment, but it's pretty low, somewhere in the range of ~.5 ohms.

 

BTW: limits on the secondary are 5000 and 8000 ohms.

 

the brake/throttle is probably unnecessary, i thought i read it only as happening when at speed. in that case, it could have been the torque converter clutch locking and unlocking constantly.

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Sounds like an issues I was having so I'll just throw out this list of things I fixed before it went away:

Brake Switch

Throttle Position Sensor

Ignition Coils

 

I was also having some weak starts, fixed these things and everythings been peachy since:

Battery post was stripped, replaced battery

Fuel Pressure Regulator

EGR Solenoid

 

Also, here's a video of one of my bad starts - car sort of stumbled after cranking - note that I did not touch the throttle, car was ramping up the RPM's itself.

[video=youtube;VDyD4Rnjnoc]

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Got the codes. Don't know if they're related but they were both egr codes. P0401 and P1406. Egr insufficient flow and egr pintle position error. Fwiw the light was on the day before this trip so I don't think they are related to the issue.

 

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The egr issue is probably the passage in the upper intake manifold clogged full of carbon build-up. The same thing happened on my 98 Lumina with the 3.1L L82. Thought it was a faulty egr solenoid at first and mistakenly replaced it. The ses code came back and I later discovered a youtube video showing how to clean the carbon build-up out of the manifold. It seems to be a fairly common issue on high mileage L82s.

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