2000 S70 (non turbo) threw code P0304 yesterday, now it's missing, rough idle. I pulled the coil pack and the spark plug. My question is should I assume the coil pack is firing because the spark plug is not wet?

Thanks for your help

tman53

It shouldn't have flooded, so it probably wouldn't be wet. However, the coil pack being bad should have set a P0354, which I assume it did not. It doesn't always throw the code when the injectors go, so it can't be ruled out just yet. How's your oil level, and how old are your spark plugs?

I'd switch the spark plug with a different cylinder (say #1) and the coil pack with still another cylinder (say #5) and see if the code travels, and where it goes. Assuming it doesn't travel anywhere, I'd run a compression test and verify the compression is proper. I doubt this will turn up anything but its another easy test to rule things out. Then I'd suspect the fuel injector or injector wiring. I'd probably replace the injector first, then hope I didn't have to trace the wires, but if the injector didn't fix it I'd look for a problem with the wiring.


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If you're not driving it "like its stolen," are you really driving?

Thanks for the info. What I did this morning was swap coil packs between #4 and #5 and now I get code P0305. I think that is pretty good indicator that the pack is bad, correct??

Yes, that about solves it. If you've got a junkyard nearby you can try to find one. It seems there are several cars its used on. But it might not hurt to bring yours with you to make sure its the right one.
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If you're not driving it "like its stolen," are you really driving?