Chrysler Repair: 1999 Cirrus Engine Miss Problem: code 0300., 1999 chrysler cirrus, chrysler cirrus

Question
I have a 1999 Chrysler Cirrus LXi 2.5L that has an engine code of P0300. I believe that is an engine miss code. I did my own testing of the problem. I started and ran the engine at idle for 20 minutes and found this out. The engine runs fine, at first, but after the engine temp gauge starts to rise, the engine miss begins. At this moment, the engine tach goes up and down as the engine misses, every 3 to 5 seconds or so (a severe problem). It continues until the engine reaches operating temperatures. At that point, I hear a miss every 5 to 10 seconds, but I can't really feel it (the car doesn't really shake), the engine tach remains steady, and there is no problem driving the vehicle. When I'm driving the car and I'm in the just higher than very cold to operating temperatures, the engine runs fine at higher RPMs than idle engine speed, but the engine will miss (sputter) and eventually stall, if at idle engine speeds and in gear. Do you have other tests for me to perform or any advice for me? Thanks.

Answer
Hi Brian
I would start by testing the coolant temp sensor located near the thermostat housing at the base of the place where you add coolant to the system. It should read 9-11K ohms when the engine is cold, and then drop as the engine warms up to about 600-800 ohms when fully warmed.
Otherwise without a fault code it is difficult to identify a specific cause and the list of possibilities for the 0300 code is very lengthy involving all aspects of the engine mechanicals:
fuel pump or filter (unlikely as regards the filter), injector harness connectors, ignition coil circuit, spark plugs, mechanical problem  (compression test would probably show that), contaminated fuel, water in fuel. pcm power ground connections, injectors, restricted exhaust, intake restriction, the pcm itself, the evap emission control system, the exhaust gas recirc valve system (this is something I would certainly recommend that you check, as if the valve sticks ajar it will definitely cause misfiring. I suggest that you lube the valve stem with WD-40 and move it back and forth with the tip of a screwdriver in the slot to be sure it is moving to a dead-stop via internal spring-action); air gap at high rpm's, other mechanical (?), and damaged trigger wheel (something to do with one of the engine postion sensor (?)). The parenthetical items are my remarks.

Roland