2003 Buick Regal rough idling

STEPHEN KARANJA

MEMBER
2003 BUICK REGAL
3.8L
6 CYL
FWD
AUTOMATIC
150,000 MILES

I just got done with a head gasket job on this vehicle. And thanks to you guys with your help about how to resolve a rocker arm and pushrod problem that I had. The car drives fine as long as you"ve got your foot on the gas pedal. However when you come to a stop, it shakes and idles very rough. Has a check engine light that's on. And code is po300. Radom misfire. So far I have replaced spark plugs cleaned injectors checked for vacuum leak the only thing that I have not replaced is spark plug wires. The problem has not disappeared. What else could I be missing. And also how come it drives so well on the freeway, the problem only shows up when I come to a stop. Tell me how I can send a donation you guys are well worth it.

3 Replies

JACOBANDNICKOLAS

MECHANIC
108,328 POSTS

Are you certain there are no vacuum leaks? Also, have you checked fuel pump pressure to make sure the regulator is doing its job and not providing too much pressure?

To be honest, a vacuum leak is felt more at an idle. Once you rev the engine, the air fuel mixture isn't as off as when it idles. So, double check that and make sure the idle air control valve (IAC) is working. The IAC is responsible for maintaining a smooth idle.