TC problem perhaps? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1987-1991 Parley with regards to your 1987 to 1991 Bonneville, Olds 88 or Buick Le Sabre Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

Reply
 
 
 
Thread Tools Search this Thread
Old 03-11-2006, 11:07 PM   #1
JB
Junior Member
Thread Starter
 
Join Date: Nov 2005
Posts: 7
Thanks: 0
Thanked 0 Times in 0 Posts
JB is on a distinguished road
Default TC problem perhaps?

Heres the situation. While driving my 1990 Bonneville LE, the RPM at a given speed has recently increased over what it formerly was. ie, at 55mph, it used to run about 1600 RPM, and now seems to run about 2000 RPM instead. A couple of nights ago, when driving home from work, i was driving with the cruise control set, and the RPM jumped up while driving on a flat piece of road, and it never came back down. It doesn't seem as if its shifting down, so am I looking at a TC problem. This problem has brought decreased gas mileage, which is costing more all the time it seems, and I would very much like to get my 5-8mpg back.
JB is offline   Reply With Quote
Old 03-12-2006, 03:19 AM   #2
Senior Member
Posts like a 4 Banger
 
Join Date: May 2004
Posts: 124
Thanks: 0
Thanked 0 Times in 0 Posts
T-Keith is on a distinguished road
Default

Get to a steady speed around 55. Without taking your foot off the gas, tap the brake pedal lightly. You should see a slight jump in RPMS. If not, try pulling the pedal back with your foot.
Two likely causes: The brake switch, which disenguages the TCC when you apply the brakes. OR, the TCC solenoid. The first is an easier fix, the second requires removing the side of the tranny case and axle. It'* actually more common that they lock up, especially on the TH125s.

-T
T-Keith is offline   Reply With Quote
Old 03-14-2006, 10:55 PM   #3
JB
Junior Member
Thread Starter
 
Join Date: Nov 2005
Posts: 7
Thanks: 0
Thanked 0 Times in 0 Posts
JB is on a distinguished road
Default

Ok, I got up to about 60, hit the brake with my foot still on the gas and the RPMS didn't climb, jsut slowly fell with mph. I gave it more gas, and it eventually downshifted. What does this tell me?
JB is offline   Reply With Quote
Old 03-14-2006, 11:13 PM   #4
Senior Member
Certified Car Nut
 
Join Date: Oct 2003
Posts: 19,756
Thanks: 0
Thanked 0 Times in 0 Posts
1993 SLE is on a distinguished road
Default

Quote:
Originally Posted by JB
Ok, I got up to about 60, hit the brake with my foot still on the gas and the RPMS didn't climb, jsut slowly fell with mph. I gave it more gas, and it eventually downshifted. What does this tell me?

if you are going 60 mph and it TCC lockup, Pressing the brake will unlock the TCC, thus causing the RPM'* to increase
1993 SLE is offline   Reply With Quote
Old 03-15-2006, 10:27 PM   #5
Senior Member
Posts like a 4 Banger
 
Join Date: May 2004
Posts: 124
Thanks: 0
Thanked 0 Times in 0 Posts
T-Keith is on a distinguished road
Default

You shouldn't hit the brakes hard enough to engage them, but it'* sounds like the TCC is not locking. The first thing to check is the switch on the brake pedal.
T-Keith is offline   Reply With Quote
Old 03-15-2006, 10:29 PM   #6
BANNED
 
Join Date: Aug 2002
Posts: 0
Thanks: 0
Thanked 0 Times in 0 Posts
banned3800 is on a distinguished road
Default

The Cruise control does function as it should then?

Almost sounding like a bad TCC solenoid

__________________
Best Car Insurance | Auto Protection Today | FREE Trade-In Quote
banned3800 is offline   Reply With Quote
Old 03-15-2006, 10:40 PM   #7
JB
Junior Member
Thread Starter
 
Join Date: Nov 2005
Posts: 7
Thanks: 0
Thanked 0 Times in 0 Posts
JB is on a distinguished road
Default

Yes, the cruise control works properly. Is the brake pedal switch going to be under the pedal in the car? Hopefully thats all it is and not the solenoid.
JB is offline   Reply With Quote
Old 03-15-2006, 10:41 PM   #8
Senior Member
Posts like a Turbo
 
Join Date: May 2005
Location: Fredericton, New Brunswick.
Posts: 380
Thanks: 0
Thanked 1 Time in 1 Post
Timothy's Buick is on a distinguished road
Default

This sounds like a stuck open thermostat. I mean, you were driving on a flat road, with lots of air flow going through the rad, cooling the coolant down, then because the thermostat is stuck open, all that cold coolant rushes in and out of the engine before it can even warm up. This gives the ECM a low temp reading, which definitly keeps the TCC from engaging. I remember last september when I had to change my thermostat, because the TCC would not engage.

To tell for sure, hows the dash temp reading?

If the brake switch was bad, then wouldn't the cruise not operate, as well as the stop lights?
Timothy's Buick is offline   Reply With Quote
Old 03-15-2006, 11:02 PM   #9
Senior Member
Posts like a Turbo
 
Join Date: Feb 2006
Posts: 220
Thanks: 0
Thanked 0 Times in 0 Posts
NCCamper is on a distinguished road
Default

I am going to say its the TCC solenoid, and not the thermostat. Only reason why is that I have the same problem, and the car was running cool, so I put in a 195 thermostat. But I still have the TCC problem. It works fine if it'* cold outside, but if it warms up outside, and the car has been running 15-20 mins, the car drops out of OD and the TCC unlocks. Too bad, because I really dont want to get into the TCC solenoid, but I have no choice. While I am at it, I will probably change the spring that smooths out the 1-2 shift. It gets kind of clunky shifting when the OD/TCC problem occurs. :(

Good Luck with yours!
John
NCCamper is offline   Reply With Quote
Old 03-17-2006, 12:26 AM   #10
JB
Junior Member
Thread Starter
 
Join Date: Nov 2005
Posts: 7
Thanks: 0
Thanked 0 Times in 0 Posts
JB is on a distinguished road
Default

I can pretty well garuantee that it isn't a thermostat. The car heats up quite well, as I still have the winter cardboard in front of radiator. The temp gauge usually gets about 1/4-1/2 the way, never farther than that.
JB is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Electrical Problem Perhaps?? BigP81 Everything Electrical & Electronic 3 08-17-2007 04:48 PM
A good place to buy your next, bonne, perhaps? impatient99 Lounge 2 04-09-2006 01:08 PM
Perhaps some math genious can help me... rjolly87 Lounge 21 01-31-2006 06:59 PM
perhaps a little extra feature would be cool. rjolly87 Forum updates and suggestions 16 04-14-2005 08:37 AM
Perhaps my funniest find on the interweb yet... PG-13 SSsuperchargedEi Lounge 15 08-26-2004 11:23 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 06:53 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.