I've been fighting a ghost,(po301)#1plug misfires,can the transmission not shifting right cause misfire reading on this van?Sometimes transmission slips when taking off,and on high speed seem like it get between gears,after it sliped engine light went out/off,engine smooths out,runs good for about four days.
Transmission Shifts Hard on 2006 Chevrolet Uplander
A poor shifting transmission will not cause a misfire, particularly not on a single cylinder. A misfire on the other hand can cause the transmission to shift erratically. Single cylinder misfires are fairly easy to diagnose and should not cost much to isolate. Best is to act quickly to avoid damage to the catalytic converter.
If the check engine light flashes as you are driving signifying a sever misfire to the point of doing damage to the catalytic converter the computer in your car may put the engine and transmission into limp mode but it is unlikely this is your problem It sounds like you have a transmission problem and a valid misfire code. The misfire could be a vacuum leak, a bad injector or ignition related problem, hard to say without seeing freeze frame data on a scan tool to identify the cause of the misfire. Maybe worth servicing the transmission and see if that helps.