1999 528i cylinder 3 low compression
My 1999 BMW 528i intermittently dropped its top speed to 20-30mph. Had the codes read by Advance which gave P0303 Cylinder 3 Misfire Detected, and P1580 Throttle Valve Mechanically Stuck. Took the car to an independent BMW garage. The garage replaced throttle body. A week later the car began to sometimes misfiring when started then ran rough, or started without misfiring and ran smoothly. Again had the codes read by Advance which gave only P0303 Cylinder 3 Misfire Detected. Today on the way back to the garage, the engine temperature began to climb into the red, so immediately parked the car and had it towed to the garage. The garage said cylinder 3 had low compression (20#s) which may indicate blown head gasket, cracked piston or cracked engine head. I asked them to pull the head and tell me what they find. Any suggestions?