Be aware that I have posted on this ongoing problem before. And yes, I
read and followed up on most (I think) of the suggestions made. Taking
from the top:
This is regarding our 1995 Park Avenue, 104,000. I call it the Herky
Jerky problem. Here it is in a nutshell:
While driving at constant speeds there will be a slight hesitation, as
if the engine had died for a couple seconds. I call it the Herky
Jerky. At the present the symptoms are mild and intermittent. At its
worst, it will occur much more frequently and with more severe
hesitation, but still not all the time. When it's that bad the
symptoms can be stimulated by accelerating on a grade, e.g., going up
a freeway interchange fly-over.
This has been going on for several months.
Some reading on the Internet (alt.auto.gm) led me to believe it may be
caused by a failing torque converter clutch (TCC). However, others
said the same symptoms can be caused by the engine missing and
recommend changing the spark plugs and wires. I did that and it seemed
to help. However, the problem then reappeared so I took it to the
independent garage that has been doing repairs and maintenance on the
car for the last several years. They replaced the air mass flow sensor
which seemed to help. However, the symptoms returned in a day or two,
or more likely had never really gone away. In fact, it started
exhibiting the hesitation so severely that the car was hard to drive,
feeling like it might not make it through the intersection when
accelerating from a stop. The garage then removed all the plugs and
did a compression test and inspected the plugs. The compression test
results were fine, but the #1 plug was fouled. That plug was replaced,
with remarkable results. The car ran perfectly for several weeks.
However, the old symptoms then began to reappear.
Today I took it to a Buick dealer that serviced the car when it was
still under warranty. I was usually happy with their work, but they
are too far away to be convenient. I did this because the independent
was clearly floundering, and I had heard the dealers had better
scanners to hook up that could read recent events, i.e., not depend
entirely on the problem presenting itself while the tech was driving
around with the scanner hooked up. Well, that turned out to be in the
fond hope category. The tech, who said he had 34 years experience,
drove it around for a while, but "could not get it to happen enough to
get a good reading." The dealer wanted to keep it over and give it
another go tomorrow. I declined, thinking it may be best to keep
driving it till it gets bad enough that it's easier to diagnose. I'm
also thinking maybe it's time to take it to the tranny shop. I had it
there once early on, but it would not do it for him in his test drive.
It's been about 70k miles since the tranny was serviced, so it might
not be a bad idea in any case, and maybe it will fix the problem.
OTOH, the fact that changing the plugs and wires had such a dramatic
effect tells me that it probably an engine problem, perhaps
stimulating the TCC to flip in and out.
So, there you have it. What would you recommend at this point?