P0301 after sitting in the rain

[RRocket]

Car sat in the rain most of the evening and when I went to drive it I got a flashing then solid CEL. It felt like a misfire. TorquePro app told me it was P0301; cylinder 1 misfire.

I'm guessing I have a cracked/damage coil pack? And to confirm, cylinder 1 is the cylinder closest to the back of the car on the driver's side?

Thoughts before I buy parts??

Thanks!

[1dmurrray]

I had the same issue on cylinder 4. Replaced the coil. No problems since. The 4 coil was a real PITA, but doable without removing the muffler.

[Ronnie38]

I'm new to Porsche repair but from what I read, you are correct cly 1 is on the left side (drivers in US) and the one closes to the rear of the car.

If I'm wrong please jump in.

[Loren]

http://www.renntech.org/forums/tutorials/article/181-34-liter-engine-parts-locations/

[xmac]

You can test the resistance of the coilpack with a simple multimeter. With the leads on the outer of 3 pins, you should get about 0.7 Ohm.

What happens sometimes is a rip or pinhole develops in the rubber insulating boot and it arcs into the head. I've pulled coilpacks where people have tried to fix it with electrical tape but the output voltage is much higher than tape is designed for. About $15 for a new boot or about $40 for the whole unit.

[RRocket]

You can test the resistance of the coilpack with a simple multimeter. With the leads on the outer of 3 pins, you should get about 0.7 Ohm.

What happens sometimes is a rip or pinhole develops in the rubber insulating boot and it arcs into the head. I've pulled coilpacks where people have tried to fix it with electrical tape but the output voltage is much higher than tape is designed for. About $15 for a new boot or about $40 for the whole unit.

Excellent info re: .7 Ohm However, when dry they could conceivably check as "ok", but when damp is when the problem might manifest itself, correct?

As far as replacing the boots themselves....how do they attach to the coil pack?

Thanks again everyone for the excellent info.

[xmac]

Not sure if it is water intrusion nor whether this is the exact cause of the CEL. They have three protruding rubber rings that are supposed to keep the elements out, but who knows what condition they are in.

No tools required to change the boot. You need to twist at the base closest to the coil housing to get the rubber to break the seal and then it should snap out when pulling on the boot. Re-install the boot and push in until you feel/hear a click.

Also, I find it easier to disconnect the coilpack wiring prior to removing the fasteners holding them in place. Make sure you also get a solid click when reconnecting. The large rubber boots on the end of the connector get in the way and make it difficult to snap back in place. I usually peel or slide the rubber back, snap the connector in place, then slide the rubber cover back into place.

[RRocket]

Not sure if it is water intrusion nor whether this is the exact cause of the CEL. They have three protruding rubber rings that are supposed to keep the elements out, but who knows what condition they are in.

No tools required to change the boot. You need to twist at the base closest to the coil housing to get the rubber to break the seal and then it should snap out when pulling on the boot. Re-install the boot and push in until you feel/hear a click.

Also, I find it easier to disconnect the coilpack wiring prior to removing the fasteners holding them in place. Make sure you also get a solid click when reconnecting. The large rubber boots on the end of the connector get in the way and make it difficult to snap back in place. I usually peel or slide the rubber back, snap the connector in place, then slide the rubber cover back into place.

As always, your replies are excellent.

What about dielectric grease? Yes or no? On the boots only? On the connectors?

[fpb111]

I recently changed my 2003 expansion tank (Pain in the A@@) This caused antifreeze to thoroughly soak #1 causing misfire.

Car has ~55k miles so I had coils and plugs on hand to change out for 60k maintenance.

Just a note here. If you are changing the tank and plug/coil maintenance is due, do it while the tank is out, much better access to #1 from the top. Unfortunately it doesn't help #4 you still have to cuss it out & in.

I used a very light coat of dielectric grease on the boot end, orange connecter seal, and *boot sealing ribs. That made it much easier to connect everything.

To get back to my point, the coil was shorting from the first joint, where the coil "Boot" connects, across the dirty, wet surface of the coil to ground by one of the mounting screws. No cracks, no puddle in the spark plug well just wet dirt on the surface. So if you pull a misfiring coil and it looks fine except for dirt it may have been the dirty surface that caused the misfire when it got wet, clean it and check the seal at the first rubber joint.

Another interesting observation, the "boot" (extension from actual coil to spark plug) doesn't have a metal clip that snaps over the plug end. It has a spring that is pressed and held against the top of the plug by compression of the two coil mounting screws.

*http://www.partsgeek.com/catalog/2003/porsche/911/engine_electrical/coil_boot.html

Edited May 2, 2014 by fpb111

[xmac]

Not sure if it is water intrusion nor whether this is the exact cause of the CEL. They have three protruding rubber rings that are supposed to keep the elements out, but who knows what condition they are in.

No tools required to change the boot. You need to twist at the base closest to the coil housing to get the rubber to break the seal and then it should snap out when pulling on the boot. Re-install the boot and push in until you feel/hear a click.

Also, I find it easier to disconnect the coilpack wiring prior to removing the fasteners holding them in place. Make sure you also get a solid click when reconnecting. The large rubber boots on the end of the connector get in the way and make it difficult to snap back in place. I usually peel or slide the rubber back, snap the connector in place, then slide the rubber cover back into place.

As always, your replies are excellent.

What about dielectric grease? Yes or no? On the boots only? On the connectors?

Not a fan of dielectric grease there so I put them in dry. The grease will eventually make the rubber soft and spongey. I think the original intent of the grease was to make sure the rubber didn't fuse itself to the spark plug ceramic and prevent corrosion on the contact. The grease also inevitably turns into a dirt magnet.

If you carefully twist the coilpack after removing the retaining screws, you should be fine when having to remove it again.

[RRocket]

Ok..I've moved the coil pack to #6 so the next time it rains we'll see if #6 acts up