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Gary, Buick Technician
Category: Buick
Satisfied Customers: 16877
Experience:  15 years master GM tech and mater ASE tech
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Buick LeSabre Custom: My 95 buick lesabre 137k miles when driving

Customer Question

My 95 buick lesabre 137k miles when driving in đ it will downshift and then hang in 3 gear. Not shifting Bach to 4th. Sometimes cycling the car of and coasting in N Restarting it will go back into 4th. . New ecm installed.. thanks
Submitted: 2 years ago.
Category: Buick
Expert:  Gary replied 2 years ago.
I am sorry for the long waitwhen it sticks in 3rd and you come to a stop and take off without cycling the key off when its acting up will it take off in 2nd or 3rd gear ?are there any codes set in the computer ?when this happens everything else like the blower motor ect.. works just fine ?
Customer: replied 2 years ago.
Sorry for typos. Using cell phone.. I took to a garage. They found 6 loose connections in the old harnesses that plug into new cardon ec computer with 3 plugs red,blue,white, in the harness. Changed the oxygen sensor.. the ecm is a odb 1.5v crossover car. So there weren't any codes for tranny.
Expert:  Gary replied 2 years ago.
so when this acts up and you come to a stop and take off will it start out in 1st gear ?everything else works in the car electrically just fine when it acts up ?
Customer: replied 2 years ago.
Yes it shifts up from 1st. But has stuck at third. More so when hot. Other time with a on,,off key .. it goes into 4th and I'd just fine. Didn't know it ecc controls transmission on this year. I checked the vacuum solinoid. It's ok. Unplugged the lockup converter plunge it tight.
Expert:  Gary replied 2 years ago.
at this point when it acts up what i am leaning towards is a bad ignition switch not powering the transmission correctly which will cause this issue especially that you key the ignition on and off then it will work is usually a sign of a bad ignition switch as that is the only thing you do to make it shift correctlybut we do not want to over look a basic sticking valve inside the valve body causing this issuethe best action to take is to have the transmission fluid flushed with a transmission flush machine that will clean out the inside of the transmission then remove all the old fluid then add all new fluidif it still does this the odds are replacing the ignition switch will correct this problem
Customer: replied 2 years ago.
I will get transmission flushed Next. Are there Any sensors that affect shifting, or gear selection? Thanks
Expert:  Gary replied 2 years ago.
just the speedometerif the speedometer is working and the brake lights work fine those are the only 2 inputs that could cause this kind of issueif it was any engine sensor you usually would have a code like a TPS code ect...keep in mind you can always get me back through this post for free with any follow up with this question any time even after you rate us here at Justanswer !don't forget to rate me here at Justanswer !
Customer: replied 2 years ago.
Is there a to clean the shift valves. Or drop the pan to access it. Car is in great shape. Just this new trans. Issue. The ecm fixed the stalling and mystery temp light. Was connectors.. thanks
Expert:  Gary replied 2 years ago.
the shift valves are located in the valve body behind the transmissions side cover there is nothing to access by dropping the bottom transmission panthe transmission flush should clean out all the valves and valve body just fine without having to physically remove the side cover and the valve body
Customer: replied 2 years ago.
Thanks.. a flush of fluid is next. Be in touch
Expert:  Gary replied 2 years ago.
sure thingdont forget to rate us here at Justanswer !