Hey guess I know this isn't the forum for a Regal but I have a GP also. Since the Buick and GP use the same powertrain I figured I might get some help here. I have this 2003 Regal (101,000 miles) w/3.8L engine and 4T65E transmission. At first the car wouldn't go faster than 40 mph and now it doesn't even want to idle. I was told that it needed a catalytic converter so I disconnected the pipe just to see if it would idle a little and no such luck. So I am ruling a converter out. I pulled the throttle body off and the inside of the intake has melted a little. I also noticed what looked like a little bit of anti-freeze inside the intake. Would a little anti-freeze leaking into the manifold cause the car to act like it needed a converter and cause the loss in power?
Is there a sensor on the motor that could cause this problem. My 2000 GP did the same thing and I continued to try and drive the car until it started to knock. Well I replaced the engine and have been driving it since. Someone told me it needed a converter too and that tuned out to be false.
Any help would be appreciated.