Severe engine shake, but only when...

[Junior28]

My car is a 2000 Bonneville SSEi.

I only have a problem with the engine shaking when the supercharger belt is on and I really step on the gas. I can slowly accelerate just fine, but when I punch it, the engine shakes a lot and the car doesn't pick up speed.

I originally thought the SC belt may have just been slipping so I took it off and drove without it to test. While driving without the SC belt, I floored the gas pedal and it accelerated just fine, no shakes or stutters. I decided to get a new SC belt, thinking the old belt had just gone bad, but I still have the same engine shake under heavy acceleration.

Any ideas on what could be going on and how to remedy this?

[nos4blood70]

Sounds like a misfire under boost only. Might be something as simple as needing new plugs or wires, or something else ignition related. What's the maintenance history on the car?

[Junior28]

This last summer, my dad and I put ACDelco spark plugs, MSD ignition coils and Belden spark plug wires in the car. Before 2-3 weeks ago, we never had a single problem related to the engine shaking. We also replaced the front engine mount over summer. We haven't done anything to the car related to the engine (just worked on brakes, rotors, etc.) since the summer though, so the reason for the shaking confuses me.

[Junior28]

We did also replace the catalytic converter over summer. Could that potentially be the reason for the problem I'm having if the cat is clogged? That only makes sense to me if I was having issues with the SC belt on AND off though, but I could easily be wrong.

[crash93ssei]

Classic symptoms of a misfire. I believe the Belden wires have a lifetime warranty, swap them out with a new set for free, at the same time or after if the wires don't fix it, replace the plugs. If all else fails it would be a weak coil, those MSD coils you have are no benefit at all over stock L67 coils just more expensive.

[Junior28]

Sorry for the super late post. Since I last was on here I've graduated from college and have been very busy. I just want to provide an update for anyone having the same engine issues as me.

Anyway, I ended up swapping all of the coils and that completely solved my issues. A few of the 'prongs' where the spark plug cables snap on were corroded which was causing the misfire.

Thanks for pointing me in the right direction!