My 94 LeSabre sometimes vibrates or shakes when going on the road. It does
it mostly when I am cruising at about 50 mph. It's something like an
hesitation but somewhat rhythmic. If I lift the foot from the gas pedal or
press it until the car shifts down that vibration or hesitation stops. It
also does it at lower speeds. It's not the CV joints or the computer. I took
it to a transmission place and they said it must be the engine, maybe a bad
spark plug, wire, etc. I replaced these and also switched the Ignition Units
and Coils with the ones from another Buick I have and it didn't fix the
problem. When I read the codes one tells me that cylinder # 5 and #6
misfire, #5 almost all the time. But when I check the spark at the spark
plugs it is strong and doesn't appear to miss and the engine doesn't shake
or hesitate. When cold it does it more and I can notice a vibration at idle
as if one spark plug wasn't working well, but not as if a wire was
disconnected. Compression is almost even on all cylinders except number 1
that is lower about 12%. However, spark plug number 4 looked dirty as if it
wasn't burning well, but not that bad. Otherwise the car run OK and starts
at the first time. Vacuum and gas pressure are normal. Any idea what may be
Check the throttle position sensor. And... clean the throttle body. I'd
clean the throttle body first since that requires not parts purchase. The
TPS on that motor is a bit of a pain to replace and to be done properly it
has to be calibrated when you replace it, but it's a fairly common failure
point. It's only a pain to replace because of where it's located. Requires
you to "get down under that part, and in between these two and behind that
one over there...".
Try gently depressing the brake pedal with your left foot while cruising
steadily at 50 mph. Keep the right foot on the accelerator so as to
maintain steady 50 mph. Does this scenario stop that vibration/hesitation?
Yes means the lockup torque convertor is at its critical parameters for
trying to decide whether to lock up or unlock. Often the simplest solution
here is to drive either a little slower or faster. No means this is not the
culprit & diagnostician needs to look further. s
Don't think 94 has an adjustment, but if it does, it'll be on a cable
from tranny to throttle linkage. Will have a flat metallic disc inside a
plastic retainer. (Has a tiny hole in the center of metal disc, for your
recognition). Press disc inward enough to allow you to slide the cable
further thru its retainer--lengthening its distance from tranny or
shortening it, just a tad, will alter the go-into-lockup speed. Try
lowering speed 1st.; may hafta use trial-and-error--no problem. HTH, s
I don't see any cable that can be adjusted and neither comes from
transmission. Just by touching the break pedal, even before the brake light
come on, the vibration/hesitation stops. I wonder if disconnecting some
switch at the brake pedal would do anything useful?
Hi, Alpha one, what is happening as you gently depress(or harder) the
brake is the lockup torque convertor is being disconnected--ie, car is not
utilizing the efficiency, gas mileage, lower rpm's, and cooling it receives
when IN lockup mode. It's vaguely similar to car not shifting into the last
gear, & would feel that way to a non-mechanic. On older cars, we could
cut/disconnect a wire to render lockup inoperative. I've personally not
known a tranny to burn up from any lack of cooling, but I've heard it will
run hotter. They did get worse gas mileage, but lockup shudder/binding when
approaching a stop would be elimnated.
Sorry, but someone else would have to tell you any repercussions or
method of permanently disengaging the '94. I think the method would consist
of finding proper wire that completes lockup circuit (somewhere near tranny)
when computer calls for it & cutting it. Were I to do it, I would leave it
where I could easily reconnect it if other malfunctions should appear--maybe
even splice in a toggle switch so I could engage at smooth rpm's &
dis-engage at critical/shuddering rpm-range.
Still think accelerating thru critical rpm-range more quickly could
pretty much 'hide' your problem, at least from you who happens to be the one
bothered at the moment.
Good luck & HTH. s
One more thought: talk to a tranny shop or 2 & ask. There may be a
lockup-control solenoid not properly or fully engaging which could be
replaced by merely pulling pan. If so, this may be a correct, permanent,
relatively inexpensive fix. Nothing beats doing it right! Luck to you, s.
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