I just replaced my spark plugs thinking that would fix the problem, wires seem to be good, ignition coils were replaced not long ago according to previous owner, although I can not verify that. It feels as if there was a miss fire in one of the cylinders, but wouldn't the check engine light come on if that was the case? It's a slight shake that can be felt more when I'm inside the car.
When I accelerate it kind of shakes too but acts normal after some more gas, while I'm stopped at a light or stop sign it does it intermittently it not continuous.
I'm about to take a 400 mile trip to AZ and I'd like to fix it before I take off so any help would be greatly appreciated, thanks.

 

have you checked the cap and rotor button ? 300 or 400 ?

 

Oh sorry it's a 93 SC400, one of the distributor rotors has a small crack but it's nothing serious, I just ordered a new one anyways, so is that the button you're talking about, the rotor?

 

I'll take pics tomorrow if I don't get a 12hr shift again, it's hard working so many hours and trying to fix the car. I'm also going to replace the distributor rotor, any ideas on what else to check?

 

Anybody? I didn't quite understand what you meant by "the cap and rotor button" Or how do I test the ignition coils.

 

its sounds like a fuel problem, when was the last time you changed your fuel filter?
When i replaced mine black gas came out the inlet side and yellow gas out the outlet.

 

you're describing exactly how my car was driving when I needed to replace the motor mounts. Maybe check those cuz that was my fix.

 

It's probably the motor mounts. They help reduce vibration and is a common issue with older SC's. They don't last forever but can be replaced rather inexpensively.

 

Thanks for the help I'll go ahead and replace the fuel filter first.

 

it's your motor mounts man, i'm getting mine changed in a few weeks. I changed spark plugs, added fuel injector cleaner, etc. and it just got worse and worse.

 

I've never replaced a mount and I don't have to... yet, anyway. For reference, how hard is it?