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94 buick lesabre on a up hill grade in overdrive only {3th gear is ok no problem} over 50 mph rpm drops to 1200 car srarts to
stammer and not enough power tap gas pedal up an down fast
rpm jumps to 1800 a few seconds later rpm back to 1200 again
with gas pedal half way down this goes on over and over until
i get to top of grade, car will shift back and rpm pick up if i
push gas pedal to the floor, but when the cruse control is on
that doesn,t happen. car motor doesn.t increse power by is self to maintain speed and keep it there 4th gear only. 3th
gear will keep rpm at 1800 up hill and not slow down?
I search the internet for a site with the same problem but no
luck, what do you suggest for this old buick?
motor runs nice and smooth and tran shift good and smooth
like a new car buick has 200000 mles on it and drives real nice
motor serviced every 3000 miles tran oil changed and new
filter 3 times Thank youj


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contributions: 2056
Images: 37
Location: Oregon
I am not sure what you are saying.

you go up a long incline and the car isn't downshifting to keep your speed up?

are you saying that your car doesn't have enough power in fourth gear (because it did before)?

is the car shifting in and out of lockup?

You say that the car doesn't exhibit the problem using to cruise control to keep speed up when going up the same incline?

tell me what did the car do under normal conditions going up this incline before you noticed it has a problem. What is different from before?

You should probably drive up this incline that causes you the problem and graph the data to see what is happening. Could be a tranny problem. Drive it with the cruise on and with it off and see what is different.


   
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HI when the car buick lesabre 94 was working ok going up a
long up hill grade motor increses rpm to 2000 2500 and
stays there untill i reach the top and motor rpm come back
to 1800 again 65 mph, now on a up pull or on a level road
going over 50 mph in overdrive rpm drop to 1200 steping on
gas pedal rpm still 1200 step harder still 1200 if i tap the
gas pedal up and down fast rpm jumps to 1800 and back
down to 1200 again a few seconds later this go on and on
until i slow down to under 50 mph and in 3 gear rpm stay
at 1800 and every thing works ok no more tapping the gas
pedal just takes more gas to get somewhere.
when the rpm drop to 1200 going up hill car stammers
because motor running too slow to pull the load
question is what makes the motor speed up to 2500 0r
3000 and stay there in [ overdrive only] over 50 mph gong
up hill thank you hope this helps you make a better
analycis note this in overdrive only 4 gear that i have
this problem


   
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contributions: 2056
Images: 37
Location: Oregon
ok, when you go up a hill you usually give the car more gas. that uses the TPS signal. the pcm sees the TPS and MAF and should unlock the converter and downshift the trans to pull the load up the hill. That's also what your cruise control will do. It will see the vehicle slowing down and accelerate the vehicle back up to speed by opening the throttle plate. The pcm will see that just like it would see you stepping on the gas and downshift to power up the hill.

Drive your vehicle with a scanner graphing all the data and see what is happening. It will tell you what the computer is seeing and how it is responding. You could also see if there are any codes stored.


   
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HI I see what you say and and every thing works as you hsve
discribed in 3th gear about the tbs maf and computer all
working together cruse control incresing speed.
but doesn't work like that in overdrive over 50 mph
the overdrive has a mind of its own and doesn't follow the
rules as you have described.
seems to have something to do with the gas peddel by
tapping the pedal up and down rpm jumps to 1800 or more
and the car pull a grade fine, but after a few seconds rpm
drop down to 1200 not enough rpm to keep up
so what is wrong with 4th gear, when 3th is ok?
driving all over in 3th gear, is bad on gas, around town ok
can't go too fast anyway bummer 4th gear


   
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contributions: 2056
Images: 37
Location: Oregon
you should take it to a tranny shop and have them drive it. They should look at the overdrive and TCC while they drive it and try to see what is happening.


   
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