I have a 1998 Chevy Venture minivan with 210,000 miles. For the past seven month, the van has had a miss or stumble that occurs occasionally. It seems to happen most while traveling on the interstate as I begin to go up a grade. The miss happens only one time per hill, it is usually very strong and harsh. I can sometime cause it to miss if I begin to increase the speed as if I had encountered a hill. The gas mileage has not decreased, nor has the power of the motor decreased. No smoke at any time and the van does not burn oil. Other than this single miss every now and then, the van runs great.
Things I have replaced or checked:
Spark plugs. (AC/Delco plugs) Plug wires, twice. Last time with Delco wires.
7X crankshaft position sensor. Fuel filter. PCV valve. Checked the fuel pressure, it is in spec and seems to change pressure properly. Both oxygen sensors. Catalytic converter twice, last time with a GM converter. New battery. Rebuilt alternator.No codes are stored, the service engine light does not come on. I have an interface and can connect the OBD II to my laptop, but this does not show any problem with the various sensors, and the OBD indicates a "pass" on all onboard tests. Any ideas or help is greatly appreciated, Terry