erratic misfire?

I have a 91 PA which currently has a AC Delco replacement motor in it with about 90K with about 230k on the car. Lately when driving it will run fine for a while and then later on will start to shudder/jerk like it is missing on a couple cylinders. If you put your foot to the floor it will kick down and take off and seem fine, but back at cruising speed of 65-75 it will start to shudder and jerk occasionally. The plugs, wires and O2 sensor have about 50K on them. Anyone have any ideas?

Hello,

Are you able to scan this vehicle for codes? Any Advance Auto parts will do this free. Possible causes include the plugs(sometimes will develop spark shutter from a bad plug making one think it is tranny related), possible burnt wire causing arcing, bad coil/coil packs etc. These are some things I'd check starting with the tune-up first, especially making sure the plugs are good. Many times the hard to solve problem turned out to be something simple for me.

Good luck.

The plugs, wires and O2 sensor have about 50K on them. Anyone have any ideas?

Tune up time :thumbsup:

I am by no means a expert.But please trust me when i say,If your car still runs rough after you tune it up.Please get it scanned.If you get any codes,and I mean any.Such as Knock Sensor,etc. Automatically REPLACE the CAM SHAFT SENSOR.
Reason is, I went through all that you are going through.After2 mechanics and 300.00 later the CAMSHAFT SENSOR was the culprit.
And I was getting all kinds of codes.But it was due to the CAMSHAFT SENSOR.
P.S. You might even get a code for the crankshaft sensor,but replace the camshaft sensor first.It is cheaper and easier to replace.