I am dealing with Cylinder Misfire p0300/P0302/P0304 codes on my Toyota MR2 Spyder and trying to get to the bottom of the issue.

Here is what I have tried so far:

  • Changed all 4 Spark plugs
  • Changed all 4 Ignition Coils
  • Checked wiring that goes into ignition coil
  • Added fuel system cleaner to the gas

So far no success.

Can someone point out what could be causing the problem, what additional tests I can perform to narrow down what part is likely causing the issue?

1 Answer 1


Instead of replacing more parts, it's time to start diagnosing. Because you've already replaced some parts we will have to diagnose a little out of order. The next thing to do is a compression test.

If that passes the next step is to confirm replacement parts are good. First swap plugs 1 and 2 and swap plugs 3 and 4. If the codes don't change, the plugs are good.

Repeat this process with the coils and then injectors.

If all this checks out we can then check the signals to the coils and injectors and check to confirm the injectors are doing what's commanded. That should keep you busy for a little while.

  • Thanks for the comment. I have already done the swap part and code stayed the same. I will do compression test. I am yet to get to the injectors as I am not confident enough to take them apart but I will do that. Can you please explain what/how to check signals to the coils and injectors?
    – Asdfg
    Jul 21, 2022 at 0:47
  • I use a fuel injector tester. These can be found online for rather cheap. There are also troubleshooting trees found in the service manual for your specific vehicle.
    – Jupiter
    Jul 21, 2022 at 11:51

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