For the past 6 years or so my Bonneville has stuttered/shuddered/bucked while applying light acceleration to maintain cruising speeds and most noticeably while climbing slight hills. This appears most prominently around speeds of 40-50 mph, and is slightly noticeable at speeds above or below 40-50 mph. However, during the occurrence there are no obvious spikes or fluctuations in the tachometer readings. Fuel economy is unchanged since purchase; 20 city, 28 highway. The car has 108k miles and no substantial fluid leaks.

To date the following things have been done to the vehicle:

1) New plug wires
2) New plugs
3) Ignition module and coil packs checked. All found to be within normal range. Coil packs tested at 5.2-5.9 ohms.
4) Complete rebuild of transmission
5) Fuel injectors cleaned
6) New tires
7) New front brakes
8) Total car alignment
9) PCV replaced
10) General maintenance (fluids, filters, belts, etc.) performed on schedule
11) Diagnostics performed twice by certified technician with no fault codes or malfunctions detected.
12) 2 alternator replacements
13) 1 water pump replacement
14) MAF replaced/serviced

I would appreciate any advice/suggestions to help fix this very annoying problem.

Well two things not on your list are Fuel pump and PCM!

94 H bodies were known for PCM problems,

I'd also try cleaning the throttle body if it hasnt been done in a while, common problem, and should be removed from car, with sensors removed. Use a spray cleaner that indicates throttle bodys on it. If that doesnt help, check your fuel pump pressure as suggested.

Ok, I checked my paperwork and discovered the PCM has actually been replaced twice; the first time in 2001 after it stalled and quit during driving, the second time was 5 months after the first fix when the car was running rough. So I guess the question is, if it is the PCM again, is it just a coincidence that the PCM has gone bad thrice or is there an underlying problem that needs to be addressed? It seems odd to me that we'd need to put three PCMs in the car in less than 2 years.

Thanks in advance!

If it were me (which I know it isnt) I would still put forth some effort to try and eliminate other minor possibilities before buying parts to replace a problem I'm unsure about, it can get expensive chasing a problem. Clean the throttle body, and check fuel pressure, and change fuel filter. My .02

Hey I have 93 Bonneville with the same problem. Very confusing. I have checked fuel pressure,cleaned throttle body and have maitained the car. Still does it. Now does yours do it all the time or whenever it fells like it. Mine does it whenever it feels like it. Sometimes I can go two days without any problems then it does it. I have owned alot of GM cars and I have never had one do this. If you have any ideas or you fixed it let me know. Thanks :iceslolan