Changed the plugs and wires last night. (Had to get intimate with my Bonnie, my forearms are sore) All plugs had good color but worn out. #4 and #6 wires were in bad shape where they attach to the spark plug. Will post results after test drive.

Replaced plugs and wires last night. Just test drove the car and still have the surging but seems not quite as bad. Definitely more power but surging occurs anywhere from 45-60 mph and at approx 2000rpm under load. When I hit the gas the tc unlocks from OD and all is well. Didn't have the problem in 3rd gear but test drive was only 15 minutes. Still have several items to check/ change

Rechecked coil primaries, tested ok. I had my meter set to the wrong scale (DUH) Pulled the EGR, pintle moves freely, FPR checks ok. So I have yet to check numbers 2,4,6 injectors and harness, MAP sensor (why not), fuel pressure at rail, blocked cat, change FF and O2 sensor (last resort).

Let's assume for a moment that the transmission valve body in my Bonnie is wearing out the TCC bore. Shouldn't the computer still generate a trouble code? Would a shift kit alleviate this? That problem as I understand should have fixed on 2000 and newer Bonneville's.

Update- Changed Fuel filter, Fuel pressure checks ok 42psi at idle, raises and lowers with throttle input. That just leaves the o2 sensor, map sensor, blocked cat or possibly a pcm wiring problem or a transmission problem.

If anyone has Ideas or thoughts as to what might be going on or what to look at next please speak up.

My car has this exact same problem. I recently changed the MAP sensor (because it died, not to fix this), and the surging remains. It's about $40 at AutoZone; save your money.

Replacing the O2 sensors may not do anything, but they should be replaced every 60,000 miles. Avoid Bosch.

Thanks for the feedback. I'm beginning to think that I have a tranny problem because the engine runs so smoothly. It acts like the TC is trying to unlock when the engine is under load and needs to downshift. When I push the gas pedal down some more it drops in to a lower gear no problem. I'm still going to check out a few more things on the engine but I need to find someone with a tech II so I can look at the tranny specifically when I have the surging.

Yeah, you'll need that or any scanner that checks TCC parameters — mainly slip. Advance doesn't have anything that fancy (to borrow, at least).

Well it's official, the Torque converter is T/U...

If the torque converter is bad and you need another one, I have 2 stock stall converters sitting on the shelf.

How much shipped to 98258? PM with reply.