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1994 BuickLeSabre V6 3.8 liters

When increasing speed the car starts shuttering. A type of shaking caused by the engine suddenly not running smoothly. This occurs most noticeably at about 50 to 70 miles per hour. ( I don't hit speeds higher than that). But I have noticed the effect at lower speeds also.

The car shutters the most when you ask for a small increase in speed or when you try to maintain speed while going up an incline. It occurs when you give it just enough gas to keep up the current speed, especially if the road is level or inclined.

Now, a most interesting thing is, if you give it enough gas, like if you’re going to pass someone, it drops a gear or changes the sound to that effect, and sounds great as it quickly accelerates.
If you ask for stronger acceleration it works and sounds and feels fine. But ask for slight acceleration, and you feel and hear the stammering.

The car idles just a little rough in park, but sounds pretty smooth in neutral. It drives pretty nice other than this.

What could this be, please.

 

what you described sound more like the symptoms of wheels that need to be balanced, or a wheel bearing. i would suggestjacking the front tires off the ground and try shaking the wheel. grab the tire at 12, and 6. then 9, and 3. should be very minimal play.


but if the wheels are ok, and you believe it to be engine related, how about a basic ignition tune up. start with plugs and wires. plugs, i would go with the delco 41-101s. or even ngk tr55 if you dont want to spend 6 bucks a plug. and wires, you can pick whatever suits you best.

 

It runs great when asked to accelerate quickly.

Doesn't that rule out the plugs and wires?


If I let up on the gas pedal, the shuttering stops right away. if I press accelerator firmly it stops right away. So, it is not the tires or the wheel bearings.

 

your methods of diagnosing are not going to rule out what is causing the problem. rough idle, and good accelleraction does not rule out plugs and wires. if you dont know the life of the plugs and wires, it may need it anyway.


as for the wheels, what you describe, is the SAME exact symptoms i have had when my park ave needed wheel balancing. but a wheel bearing is also a common problem on these H andC body platforms. thats why i suggested to changing it.

 

I have a 94 Lesabre as well, and it was doing something similar to what you describe. Ended up taking it to a shop, and it was a bad plug wire and coil pack. The mechanic said it was probably the plug wire that went bad first, but the electricity eventually ruined the coil pack as well. So a new plug wire and coil pack from a junk yard andlabor to fix the thing came to under $100.

 

I agree with Johns_79. I've had two older 3800's do the same thing, and it was the coil packs. It sounds like that's the most likely cause.

 

but if a coil packwas out and he is running on 4 cylinders, why does it accelerate smoothly.

 

I changed all spark pugs and wires.


Still the same. Have not checked the coils.


Thanks for the input.


I have read some about a camshaft position sensor being needed for adjusting the timing on acceleration and inclines. How does that seem to you guys?





Edited by: scaryslow

 

if you want to check the coils, read this http://www.bonnevilleclub.com/forum/...e=article& k=33&highlight=coil


but as far as the cam position sensor, it controls the timing of the fuel injector pulses. but, that will not cause a shutter. even if that circuit was open, the pcm will go to a default setting which will not be right, but the driving conditions are usually not even noticable when those fail. I had my buick with a loss of cam signal for well over a year, (before i eventually replaced the magnet in the cam gear), I took a road trip and still got 24 mpg with this problem. and you would have a check engine light on if that was the case.





do you notice any rattling at idle? maybe the balancer is worn. the rubber in those wear after time and can cause a shutter.

 

How do you test the coil pack?