Be aware that I have posted on this ongoing problem before. And yes, I
have
read and followed up on most (I think) of the suggestions made. Taking
it
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:

Symptoms

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.



History

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?

Ed

Ed wrote:
Has the fuel pressure been measured?
What was the reading?

Ed wrote:
I still favor the TCC theory. It's very sensitive to engine
vacuum/torque so perhaps the plus altered the operation slightly. I
don't know why you can't disconnect it for a test. Maybe it's not as
easy as just pulling the plug as on older models.

Ed wrote:
1. Fuel Pump
2. EGR Valve.




--
Thank you,


CL Gilbert
"Then said I, Wisdom [is] better than strength: nevertheless the poor
man's wisdom [is] despised, and his words are not heard." Ecclesiastes 9:16

"Al Bundy" <MSfortune (AT) mcpmail (DOT) com> wrote

Just to throw another theory on the floor, I had a '92 Park Ave that acted
in a manner similar to the OP's description. Turned out to be the TPS.
Replaced it, did a seat of the pants adjustment because I didn't have
anything to properly adjust it with at the house, and all was well. I don't
recommend the seat of the pants adjustment technique, but I was on the spot
and had to do something - got lucky. I would look at the TPS though.

--

-Mike-
mmarlowREMOVE (AT) alltel (DOT) net

Paul,

Thanks.

Not that I know of. I'll ask the techs to be sure. I have a fuel
pressure gauge myself.
Is there a test port on the Park Ave?

Ed

"« Paul »" <"=?x-user-defined?Q?=AB?= Paul
=?x-user-defined?Q?=BB?="@houston.rr.com> wrote

Al,

Thanks.

I had/have similar thoughts. That is, there are two things going on.
One, the TCC is on the verge,
and misfiring of the engine causes it to drop out, amplifying the
effect of the miss.

I have been told it can be disconnected, but the tech was reluctant to
do so as it causes the Check engine
light to stay on.

Ed


"Al Bundy" <MSfortune (AT) mcpmail (DOT) com> wrote

Thanks, Mike.

I can see the TPS causing problems while accelerating, but can't see
why it
would cause missing while driving at constant speed. But, when I get a
plan
of attack I will be going back to the dealer or an independent garage
and
will have them check

Ed




"Mike Marlow" <mmarlowREMOVE (AT) alltel (DOT) net> wrote

Thanks, Gilbert. I can see a fuel pressure issue, but how can the EGR
valve cause this? Any way
to check it?

Ed

"CL (dnoyeB) Gilbert" <Fake (AT) ThisOneIsFake (DOT) com> wrote

Ed wrote:
If EGR opens up then the fuel mixture will have less oxygen. If it does
this at the wrong time, you will loose power. It acts pretty much just
like a bad fuel pump if its sticking open. If it sticks closed then you
may get an engine knock if your computer is not able to compensate.

Note: I have had this happen twice to my car. As well as adding fuel
pumps about every other year for 10 years. The symptoms on my car were
indistinguisable. Not enough fuel vs. not enough oxygen is pretty much
the same thing. OBDII should diagnose the EGR problem though. However,
my 95 Blazer had OBDI so I can not be sure what your 95 park Avenue has.

--
Thank you,


CL Gilbert
"Then said I, Wisdom [is] better than strength: nevertheless the poor
man's wisdom [is] despised, and his words are not heard." Ecclesiastes 9:16