01 Mazda 626 2.5 misfire code

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#1
I have a misfire code consistantly on one cylinder. I have put in new plugs and wires, cleaned the coil pack (for tracking), checked the ohmeter rating for each bank on the coil (all 13.75), swapped plugs to check for a faulty plug. On cold start (heated parkade so not really cold) it starts with no problem but when put into gear I can feel the hesitation or miss. This is not enough to trigger the check engine light. On load such as going up a hill the light starts to flash and then stays on steady when under low load. The light either flashes or stays steady depending whether under load or under no load. When warmed up and under hard accelleration it may stumble a bit - or not. Very frustrating. Any suggestions out there?
 

Paul

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#2
Start with the code number,which one?
 
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#3
My reader indicates P90302, 1of 1, Mod #10, Cylinder 2 Misfire Detection. Reader is OTC 3408 if this helps. One thing that I had forgotten to mention is under partial acceleration up a shallow hill I had some backfiring, or at least the car was backfiring!
 

Paul

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#4
You really need a scan tool for an in depth diagnosis.I would take a look at the fuel injector and its wiring for cyl no 2 to see if its doing its job.What led up to the problem?Did this occur suddenly or was there some other problem as well?
 

fix_it

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#5
I normally don't work on too many imports, but I would look at the spark plug wires. You probably have a bad one on the #2 cylinder. You did not say that you checked them. Use an ohmmeter and check the resistance of the wires. The longer the wire, the higher the resistance can be, but I'm not sure the exact spec. I'd thinlk they all should be close in value. If you have an open wire or one with very high resistance, I'd replace the whole set. This sounds to me like a secondary ignition problem.
 
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#6
I know I'm a little late getting around to responding. I found the problem after doing a little sleuthing and trying out hunches. First, on distributorless ignition the plug wires can be swapped on the coil module side to side. i.e. on the mazda 6 there are three rows of two and each row is interchangeable. By swapping the wires on the module and running the engine I got a misfire code for the other plug. Therefore the module had to have a dead or dying cell. So, put in a new coil module and of course put the wires in correct location and it runs perfectly. Just thought the information might be handy. I'm quite sure this setup is the same for other distributorless ignition systems. Sure gives confirmation on the problem before springing the dollars for an electrical part that is normally non returnable.