[plano-doug]

How does the bottom of the #1 plug well look? Is there any oil down there? The 1.8's are prone to valve cover leaks which allow oil to seep into the well and short out the coil, which can damage it, as well as causing a misfire.

As I recall, the gen1 1.4T valve cover gaskets are prone to doing that, too. (Hopefully somebody with one will chime in here.)

When you swapped plugs and replaced the coil module, did you notice any oil on the #1 boot?

Doug

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[plano-doug]

But how many for #1 cylinder, intermittent causing the coil to burn up. It is possible the injector could be bad too. Only has a P0301 code.

The injector may cause a misfire, but will that kill the #1 coil?
That said, inspect the wiring at the #1 injector to be sure it's not damaged.

The other thought I had is, maybe the #1 plug is somehow bad leading to misfires and coil failures. Maybe there's a hairline crack in the ceramic, for example. Try swapping plugs 1 and 2, and see if the misfire moves.

Lastly, inspect closely the wiring going to the coil pack. I can see how a damaged wire could cause misfire, but not sure how that would kill the #1 coil. Nonetheless, make sure the wires are not damaged at the connector.

I've seen someone get a bad coil module right out of the box, but you've replaced it twice now, right? So I'm thinking the problem lies elsewhere, but I'm about stumped.

Doug

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[plano-doug]

How about compression?

I'm sure that can cause a misfire. But it won't kill the coil, right?

Doug

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[plano-doug]

How do we know the coil is dead?

What we know is the cylinder isn't working. For whatever reason. Dead coil is being assumed.

Good point.

The OP, Abo1775, after replacing the coil module, did say "Been driving perfectly fine for almost 3 weeks, and again started missing on cylinder 1." So that makes me think the #1 coil is indeed bad.

But maybe not. He can ohm out the coil - if #1 is shot, it should have decidedly different readings than the other 3.

And that may steer us elsewhere, such as to a bad connection on the coil module. Maybe plugging in a new coil module restored a poor connection, but now it's worked its way open again, after a few days of driving.

Thinking out loud...

Doug

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[plano-doug]

I was having the same issue as the gentleman & i noticed quite a bit of oil residue on my plug & in the well. Do i have a valvke cover leak you think?

Probably.

Doug

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