HELP - I get a strong shaking ~3,000RPM

[bishopfredpickering]

I've got a '97 Cobalt 23LS with the VP 7.4GL DP - only ~170 hours. It cranks fine, idles fine and then I get a pretty strong engine shake around ~3,000RPM, but absolutely no shake until then. I've recently had the plugs, carb and distributor cap replaced.

I suspect two possibilities - fuel issue (failing pump, restriction, water in gas) or EEM issue (bad module, bad sensor(s), corrosion on a sensor, etc.) that's kicking the engine into SLOW mode. Seems like SLOW mode engaging would gradually reduce the engine speed w/o the shaking? I realize I'm screwed if the EEM itself is bad as this is out of production.

Any ideas?

 

[bishopfredpickering]

Should also point out that compression has been checked on all cylinders and tested good. The shaking happens when I rev the engine in neutral or when the drive is engaged, so I'm leaning towards an engine issue rather than drive.

 

[Bondo]

I've recently had the plugs, carb and distributor cap replaced.

Ayuh,..... Welcome Aboard,....... I'd suspect the previous work done,.....Verify, before movin' to other causes,....