I have a 2007 GS350 which intermittently runs rough with engine misfires after a cold startup. After the cars been sitting for a while then driven, the RPM's will drop from 600 to 500 or so and fluctuate when idling in gear.

I've seen the GS300 has a CSP program for carbon buildup and a piston ring repair. Has anyone had the same issue with a 350?

 

When was the last time you replaced spark plugs and air filter? If you haven't I would do so

 

The air filter is new. I dont think the plugs have been replaced yet. I doubt it would be the plugs though, wouldnt it have a misfire all the time then? This is a pretty intermittent problem.

 

Nope plugs can give you a misfire and clear up. Are you getting any check engine lights? You may aswell do a top engine cleaning, and cleaning of the throttle body. Those do get dirty! That too can cause a misfire at start up.

 

when I read the title "misfire" I think of the 350 right away. But I see your sn is 430, I want to check it out cause mine is GS430 too. Now I see it is actually 350.

Goodluck buddy.

 

The problem seems to be getting worse, the car acts an awful lot like the 300's with the bad piston rings. This worries me.

 

Replace plugs, top engine clean, and clean throttle body. When I pulled my throttle body out it was filthy.