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I have a 2004 mazda6 3.0 that's misfiring on cylinder I changed coil pack spark plug and fuel injector and it still misfiring on cylinder 3 when I brought the car 3 years ago the owner did away with the catalytic converter so the car has no catalytic converter and the check engine light stays on but it flash when the engine misfire. What can be the problem
 

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I have a 2004 mazda6 3.0 that's misfiring on cylinder I changed coil pack spark plug and fuel injector and it still misfiring on cylinder 3 when I brought the car 3 years ago the owner did away with the catalytic converter so the car has no catalytic converter and the check engine light stays on but it flash when the engine misfire. What can be the problem
I would say faulty wiring or connector. I have a 2004 and I swear you have to be a brain surgeon whenever touching the wiring and plastic bits. My Toyotas never had this issue even when they were 30 years old. It is possible that you dropped compression in that cylinder as well. You can use a screw-in tester or you can disable either the ignition or the fuel and check the starter motor current waveform. You can also do this by ear if it is bad enough to have a cylinder that is not firing. The rrRrr, rrRrr, rrRrr, rrRrr, of the motor compressing each cylinder will change in rhythm as the low compression cylinder moves a lot faster. Kind of a rrRrr, rrRrr, rrRrr, rrrrr, rrRrr, rrRrr.... that's a technical description by the way.
Good luck.
 

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Have you been driving it for a while and then you had a misfire or was the misfire still there after putting everything back together?

Bad part is you will have to pull the intake again. What to check:
  • Just like DFG mentioned check that the power connection to the coil is good. They become brittle over time and don’t click in very well. I ended up small zip ties around the connector and coil after the connector clip failed.
  • Check the ohm reading on the coil with another. They should be close to each other. Don’t buy cheap coils, it’s not worth the time and effort. New cheap coils can be bad from the get go. Denso or NGK.
  • Like DFG suggested do a compression test. If the previous owner pull the cats there was probably a reason. Pull the fuel pump relay and unplug the other coils. Since the intake will be off you won’t have to worry about the electronic throttle body being closed.
A tip that I used to remove the intake. The bolts are captured in the intake but always hang up in the threaded hole fighting you to lift the intake off. I purchased some clear vinyl tubing that fit right over the flange of the bolts. After unscrewing the bolts I slipped the tubing over the flange of the bolts until it was seated on the manifold. This stops the bolts from dropping down.
After the intake was off, I would push the bolts farther into the tubing. Makes the job way easier.
John
 

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Discussion Starter #4
I would say faulty wiring or connector. I have a 2004 and I swear you have to be a brain surgeon whenever touching the wiring and plastic bits. My Toyotas never had this issue even when they were 30 years old. It is possible that you dropped compression in that cylinder as well. You can use a screw-in tester or you can disable either the ignition or the fuel and check the starter motor current waveform. You can also do this by ear if it is bad enough to have a cylinder that is not firing. The rrRrr, rrRrr, rrRrr, rrRrr, of the motor compressing each cylinder will change in rhythm as the low compression cylinder moves a lot faster. Kind of a rrRrr, rrRrr, rrRrr, rrrrr, rrRrr, rrRrr.... that's a technical description by the way.
Good luck.
Drfeelgood you was right it was a bad connector I bought a new wire harness and once I put it on the misfire stop I had a hard. time putting it on but I got there thank you
 
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