Unknown Engine Problems: Shaking/Misfiring

Recently I’ve been experiencing some intermittent engine problems, particularly when it is damp outside. The problem occurs after the vehicle has just been started for the day and I start accelerating. When I stop at a light the engine begins to shake, then when I accelerate it still feels like the engine shakes and has trouble picking up to accelerate. After driving for a few minutes the problem subsides and I don’t experience it for another few days, or until it is foggy/damp outside.

I took my truck to a garage to get things checked out but they couldn’t find any clear problems (no arced wires). Does anybody here know what that problem might be?

Vehicle: 2002 GMC Sonoma

When an engine runs rough when it’s damp/raining/foggy, it usually means the secondary ignition components are being effected by the moisture.

Depending on the vehicle, this includes the spark plug wires, distributor cap and rotor, and the ignition coil.

If you can’t remember the last time these components were replaced, that’s where I’d start.


No “check engine light” ?

No, the “check engine” light is not on.

I agree with @Tester advice. You might also look for a vacuum leak in the manifold area.

The 2.2L has an ignition module and spark plug wires. Replace wires. The 4.3L has a distributor, coil and wires. Relace all and move on.

Looks like the guys have this figured out for you. Old plug wires are usually the cause for running bad when it’s humid outside. Sometimes the heat from running the engine will bring plugs wires back to life somewhat but they need to be replaced.

“no arced wires”

Bad ignition wires can look OK, and test good on an ohmmeter too.

Would be nice to hear from OP again