erratic misfire?

[clauritzen]

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?

[82Stang]

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.

[wrightz28]

Originally Posted by clauritzen

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

Tune up time

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.