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