I have a 2004 RX8 MT that's having starting issues (one coil intermittently fires and doesn't spark on start up). I have narrowed it down to a faulty ECU/PCM. All the plugs, leads, coils, harness, and grounding are all fine so I have ruled those out. What I want to know is if I can just buy another 2004 MT ECU and plug it in and have it run? Or will I need to take it to the dealer for some sort of programming. Really not sure what to do would like some advice thanks.

 

What makes you think it's related to the ecu?

 

This is why, also a mechanic had that suggestion too but wasn't sure.

 

How do you know the coils are fine if one is not firing intermittently? What procedure confirmed they're fine? It's the most common failure point, and one of the cheapest to correct.

Did you swap the coils around to see if the misfire travels with the coil?

Does yout mechanic have a history successfully fixing RX8s? If no, then start over.

 

I used an induction light on all of the coils, and one did not fire. Then I switched the connections on the back of coils to the one that did not fire and then it did fire, but the other one didn't. So the coil itself is fine. And yes, he is a rotary specialist who has been in the business for a long time.

 

You'll have to pay $200 for the dealer to marry the new ECU and your immobilizer... but this would be the first time I've heard of an ECU causing a spark problem.

 

What makes u think its not the harness? Have u probe each wire?

 

I would also recommend that you check the harness.....often the wires get brittle going into the plug a and can loose connection