Chrysler Repair: 01 Eclipse Random Misfire, eclipse spyder, egr valve

Question
I have a 2001 Eclipse Spyder Gt 3.0 24 valve, 105,000 miles. It has a nasty misfire and idles terrible. When the engine is cold and on the highway it acts pretty normal. It misfires at low rpms and at idle after it warms up. The check engine light is on and the code i get is p0300 which is a random misfire. I have replaced all spark plugs and wires, distributor rotor and cap, and egr valve and at no point has it gotten even a little better. It has just seemed to get worse even after i replaced each part. I need help! I took it to a Mitsubishi dealer and got a print out of what they would fix and I have fixed all of it as described above. I have a friend that is a good mechanic and he is out of ideas. I am already out about $1000 and the car is still almost undriveable. Any suggestions would be great. Also, after i replaced the egr valve another code showed up along with the P0300 it is P0401 which is a bad egr valve code? Thanks.

Answer
Hi Greg,
I wonder about the engine coolant temp sensor might be not accurate. Does it read around 1,000 ohm when the engine is warm? If not, and it reads higher resistance than that, it may cause a too rich mixture when the engine is warm.
Getting the 0401 suggests that you might want to check the vacuum supply to the valve and also the solenoid wires to the pcm. Also notice if the valve stem is fully closed at idle/warm while the engine is missing. If not, then that is why the rough idle.
Here is a recent answer I sent about the 0300 code:

"The manual gives the following possibilities, in addition to the wires which were replaced:
fuel pump or filter (unlikely as regards the filter), injector harness connectors, ignition coil circuit, spark plug, mechanical problem (but compression test would probably have shown 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 be checked, as if the valve sticks ajar it will definitely cause misfiring). So suggest that he 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.
Many of these also might set a separate code so he might not need to concern yourself with them. But the egr valve would be high on my list.
Let me know how this progresses, please.

I was unaware that the 3.OL came in a 24-valve mode. I don't recall it being used in the domestic Chrysler line. I don't have the wiring diagrams for that if it is, unfortunately.
Roland