I have a 1998 Buick Ultra with 103,000 miles. Problem is @ around 3000 rpm just as the transmission shifts up the car starts to shutter. After upshift car runs smooth until next upshift. Sometimes I get a code 0304 (#4 misfire) when this happens. Also engine will not run over 4000 rpm. At 4000 rpm (whether in park or driving)car starts to misfire severly. Have changed plugs,plug wires and (1) coil pack for Cyl's 1,4. No change. Any help???

One thing to remember here... The module uses a drive transistor to operate the coil. If it does not operate the coil, th3e same misfire will occur. Food for thought. Ray

[QUOTE=RABarrett]One thing to remember here... The module uses a drive transistor to operate the coil. If it does not operate the coil, th3e same misfire will occur. Food for thought. Ray[/QUOT

Where is the drive transistor located ?? And is there one for each coil pack?? After changing to new plug wires it has become less frequent but the car still jerks (and code 0304)sometimes when it upshifts, and still nothing greater than 4000 rpm's. Also, how many times must the computer sample a fault before setting a code ???