I recently changed the spark plugs and car ran great for about 300 miles. It now runs rough after the temp starts to rise. I don't have any codes coming from the dash light when I do the ignition key on/off. I have checked the coil pack with multimeter and resistances are correct, spark plug wires ohm out fine and the spark plug appear to be firing fine ( no discolored or wet ones). I have checked the vacum lines and have not been able to find any leaks. I am going to check the function of the EGR valve. I think the O2 sensors would cause this also but since not getting any codes flashed at me can I discount these. Need help with other possibilities. I don't have a scan reader but I have read where AutoZone parts stores will read codes for you. Can they read the 1994 codes since they are not OBD 2.

 

The fact it doesnt run rough until it warms up will be the key. Does it ping
(spark knock) on acceleration. If it does it should be the egr. During cold operationand at idle,the egr solenoid circuit is grounded by the computer to block vacuum to the egr valve.When the solenoid circuit is not grounded by the computer,vacuum is allowed. when the temp sensors indicate that and send that message to the computer. if its too dirty from carbon it wont open enough because its stuck. need more symptoms and or informtion.

 

I do not get any spark Knock. I have pulled the EGR valve and tested, it was ok, no carbon and valve moved under vacumn and held. I have also checked the EGR transducer and it appears to be working. Seems to me I remember having a bad O2 sensor, and didn't get the code from the key. I am currently trying to get a scan tool and going from there. Would a plugged fuel filter have same effect.

The car appears to be missing worst at about 45 mph and when you accelerate rapidly. The power when accelerating is diminished, but it really bucks at 45 mph up to 60.

 

This may sound crazy to you but when you mentioned bucking and the fact the engine had to be warm all I could think about was a 91 Olds Cutlass. I changed everything but in the end it wasn't the engine it was the transmission. The solenoid (torque converter clutch solenoid) it's purpose is to stop all slippage and once the vehicle reaches about 45 miles a hour it is activated to lockup the torque converter tight to the flywheel for a 1-1 ratio. The best thing to do with the (Olds Cutlass) was simply pull the plug (disconnect the plug) on top of the transmission and it (the problem) never happened again. I know your car is not a Oldsmobile. Go to the Chysler garage and just ask one of the mechanics if this could possibly be the problem also tell him all your symptoms. Usually the garage doors are open and you can just directly talk to a mechanic. Good luck.

 

I finally found the problem. The coil pack was bad. I had ohmed it out according to the shop manual and it was within specs, but once it heated up it did not function correctly. Had to take it to a garage to finally find it but back on the road wiser and poorer.