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'86 Buick Century, torque converter not locking up
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hrc200x
Novice
Feb 1, 2008, 4:31 PM
Post #1 of 10
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'86 Buick Century, torque converter not locking up
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Car is a '86 Buick Century, 4 cyclinder engine, 3 speed tranny (th125?). From what I can tell driving it the torque converter isn't locking up. Would like to fix problem to increase fuel milage. Blue plugin on front of tranny is plugged in. Trans fluid is nice and red. Thats basically all I've checked so far. Car had been sitting probably 6-8 years and started once a year just to circulate fluids.
Things I should check:
Is there a way to test a brake switch? I think its located by the brake peddle?
Adjust kickdown cable? how?
Any fuses or relays to check?
Do temp sending units play a part in lockup?
I drove a '85 Century up until a few weeks ago when it died. Had this car as a back up so am retiring the '85 and going to use this one. The '85's TC wouldn't lock until about 3 miles after leaving home and that was after warming up a bit in the yard. This would make me think to check temp senders on the '86. Also on the '85 cruising along 55mph slowly put on the brakes the TC would unlock. Maybe on the '86 the brake switch is mis adjusted or bad. Does this same switch unlock TC and put on brake lights?
Need some ideas while the weather is still warm here in Minnesota.
Thanks.
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hrc200x
Novice
Feb 2, 2008, 10:11 PM
Post #3 of 10
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Re: '86 Buick Century, torque converter not locking up
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Thanks that helps a little.
"If the lockup fails to engage, there will be some slippage and fuel economy will drop. Causes here include a bad lockup solenoid, incorrect sensor input information to the transmission controller or PCM (typically a speed sensor) and hydraulic control problems."
Where is the lockup solenoid located and how to test it?
This model might be to old to have a speed sensor?
Don't know what hyd control problems are.
I think the 3 or 4 things i mentioned in the first post might be easier to try to troubleshoot first, just am not sure they could be part of the problem or not. Thats what I'd like answers on. Anyone know of any more good auto help web sites?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Feb 3, 2008, 4:03 AM
Post #4 of 10
(2434 views)
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Re: '86 Buick Century, torque converter not locking up
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Use a test light for brake light switch.
The TC lock up is more likely load dependant than temp. Load is greater when cold and fluid is thicker. Changing trans fluid would likely help. THAT'S A LONG TIME TO LET A CAR SIT so expect some troubles,
T
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hrc200x
Novice
Feb 13, 2008, 3:08 PM
Post #5 of 10
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Re: '86 Buick Century, torque converter not locking up
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Does anyone have a manual for this particular car? I looked under the dash at the brake switch. It appears there is two, one mounted higher than the other. I took out the lower one. It has 5 electrical prongs total. One group of 3 that is about 1/2 way down the switch off the side, and the last group of two prongs that are off the end of the switch. The 3 prongs on the side all ohm fine, the two on the end don't ohm at all. I took the black plastic cover off the switch and it appears that the 2 prongs on the end should ohm when the switched is pressed in. Tried bending the innards of the switch to make somthing work and it wouldn't go. Headed to NAPA in a few seconds to make sure the right switch gets ordered.
Would be nice to find someone with a manual so I know if these two prongs that don't ohm are even for torque converter lockup?
The brake lights did work before I started this project.
It is different than the '85, I pulled the 85 switch out to hoping to just swap, but different ammount of plug-ins.
(This post was edited by hrc200x on Feb 13, 2008, 3:52 PM)
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way2old
Veteran
/ Moderator
Feb 13, 2008, 4:54 PM
Post #6 of 10
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Re: '86 Buick Century, torque converter not locking up
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Click here and see if this site is of any help. May not help, but it is free and has a lot of information. Good luck.
Being way2old is why I need help from younger minds
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hrc200x
Novice
Feb 14, 2008, 9:42 AM
Post #7 of 10
(2407 views)
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Re: '86 Buick Century, torque converter not locking up
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Thanks, That site helps a bit, the wiring diagram was nice, but kinda vague. It showed only two wires going to the brake switch, and I think I have 5. But the two it did show went to the tranny, so I might be in luck.
Whats the correct way to adjust the kick down cable?
I pushed in the button, moved the cable down, let go of button, gave it full throttle and nothing adjusted. Pushed the button, moved the cable up, let go of button, full throttle, and nothing happens. Is the whole button mechanism supposed to move when you slide, or just the cable?
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hrc200x
Novice
Feb 14, 2008, 12:30 PM
Post #8 of 10
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Re: '86 Buick Century, torque converter not locking up
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Just took it for a test drive after new brake switch and I don't think it helped. Car is really quiet (unlike my old one) so hearing shifting/lockup is hard, but I"m pretty sure its not locking up.
Tried adjusting kickdown cable, brought cable all the way up, held button in a bit, moved throttle to full and it seemed to adjust its self, just needed a hand by me pushing in the button a bit. Still don't think that worked either as going along 50 or 55 mph kick down throttle and it stays in drive.
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hrc200x
Novice
Feb 14, 2008, 2:25 PM
Post #9 of 10
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Re: '86 Buick Century, torque converter not locking up
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There is no check engine light on, but I figured for the fun of it I'd get the codes and see if there are any, to my surprise there was a code 21. Is code 21 - Accelerator Pedal Position 1 Circuit High??? Where do I start looking to troubleshoot code 21?
I also adjusted the kickdown a little tighter than the spot it sprang to on its own and now 45/50 kicking down will drop it to 2nd gear.
Update: cleared the code and drove car a bit, code didn't come back, so must have been an old one. I'm kinda leaning towards the TCC solenoid being bad, but just wondering if there is a way to test the two wires going into the front of the tranny to make sure I'm getting power to lock TCC? Should it have power all the time, or just when around 45mph when TCC should lock?
(This post was edited by hrc200x on Feb 14, 2008, 8:52 PM)
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hrc200x
Novice
Feb 25, 2008, 6:58 PM
Post #10 of 10
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Re: '86 Buick Century, torque converter not locking up
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Since my last post I've replaced coolent temp senders, they were used ones from a car that lockup did work on. Put in a brand new TCC solenoid, and it still didn't help, while out today I pulled over and tried pushing really hard on the plug in on front of tranny, till thumb hurt. Drove awhile and 50 mph to my surprise TCC locked up. But ended up kicking out in less than a mile. Pulled over, pushed on plugin, lock up worked, but kicked out. Did this whole routine a couple more times. Last time it kicked out I turned around and headed home with out pushing on plugin and lockup worked. Either it was coinsidence or the problem is in order to get lock up the car needs to come to an almost complete stop.
Seems I just got as close as I've ever been to solving the problem. Hopfully soon.
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