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Discussion Starter #1
Hello all

Fiat 500 sport 2012 running on 3 cylinders, throwing P0304. 50k miles on engine.

Compression check on in cylinder 4 is 200psi
tested all coil packs - from the 1-3 pin, all reading 0.7 ohms
plugs look ok.
Swapped cylinder 3 coil pack and plug to cylinder 4, same code fault on cylinder 4
spark plug in 4 is wet, so its getting gas.

next step is to swap injectors. how about the wiring loom failing?

Any other ideas?

Thank you.
 

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You have oil on the valve cover especially nearest the battery? There's an o-ring where the pcv box attaches to the valve cover that leaks oil into the spark pug holes. Try replacing the o-ring too. Hopefully the oil has been changed regularly. The multivalve cylinder head is very dependent on clean oil.
 

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Discussion Starter #3
Thank you very much for the reply.

There is a little oil on the plug, but the plug is still firing (pulled fuel pump fuse, and observed spark plug sparking). I also swapped coils and plugs from a firing cylinder, but still #4 is not firing.


Is the problem with the oil fouling of plugs? Or something else related to the multiair system?

My next step is to remove the intake and swap around injectors (yikes, removing that looks like a task).

Thank you all for any help.
 

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Discussion Starter #4
concluding this post.

I swapped plugs, swapped injectors and was still getting a misfire on 4. The plug was wet with gas, so I thought I had good injector. I checked compression which came up strong on 4. I bought a new injector for 4, thinking it might be clogged or not spraying correctly.

To get at the injectors you need to remove the intake manifold. There are three bolts on the top, and four on the bottom. To get at the bottom bolts you need to drop the starter, and even then its a real bish to get at them. I can not imagine doing this without having the Car in the air. It took me about 3 hours to get all the bolts off, really tight conditions.

Anyway, it turned out to be a bad injector, problem solved.
 
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