boldlybold

Hi everyone, I’m looking for next steps in diagnosing this problem.

2007 Boxster S with 90k miles. I replaced all spark plugs and ignition coils about 1 year and 6000 miles ago.

I was driving yesterday close to home and noticed a rough engine while accelerating at half throttle. The engine was not fully warmed up yet. CEL came on and then started flashing. Obvious misfire symptoms so I turned around and drove back very gently. I got codes P0300 and P0303 - misfire on cylinder 3.

I’m very familiar with coil pack issues form my past driving Saabs, so I keep a spare used coil and plugs in the trunk. Today I swapped cylinder 3 plug and coils for the spares and had same issue, flashing CEL at idle, and codes. I have yet to swap the parts with another cylinder but I’m suspicious it’s not the plugs or coil given the recent replacement and swap I did today.

I am due for an oil change and low on gas (not yet to low gas light).

Any thoughts on the next steps to diagnose this issue? After doing some research, I’m seeing a lot of cars with misfires on a full cylinder bank, but not a single cylinder that is not fixed with plugs and coils. Thanks!

bluebonnet

I am fixing this myself, although I have never replaced the coil packs so am doing them as both PM and a potential fix. If it is not the coils, plugs, my next guess would be crankshaft or camshaft position sensor. Fuel injectors could be suspect.

Bad O2 sensors or a weak fuel pump could also starve fuel enough to miss on all cylinders at random.

Essentially, anything that disturbs fuel, air, or spark delivery to the cylinder would cause it to miss. Missing on multiple cylinders would point to something common to all.

boldlybold

This ended up being a wiring issue - the clip holding the connector to the ignition coil on cylinder 3 was broken, and it must have come off while driving. For now, I’ve got a zip tie around the connector and it seems to be holding. I appreciate the reply bluebonnet and I’m glad I didn’t need to go into anything more in depth!

vanlieremead

Thanks for the issue closure. We don’t get that enough.

cavediver32043

Bank 1 cylinder 3 and bank 2 cylinder 4 coil boots can get twisted when pulling back to disconnect coil connection which if not noticed can prevent the proper re-connection/ seating of coil electrical plug. The coil boots are molded and go on one way.

Corvetteboy6988

Ok, I found a little mirror for my boroscope.
the best i could tell, no scoring at least up high.
left side is top of cylinder in each picture.
i do see a streak of oil in one small spot, 2nd pic. I believe that's the valve above it that's oily too
makes me wonder if valve seals. The 1st pic is oil streak further down the cyl wall. No scoring by it unless next to or below piston.
the light band that runs vertical in each pic, which would be horizontal on the cylinder, is reflection from the scope camera.
I need a better boroscope, lol.

Would cyl 3 and 4, 7 and 8 leak more due to oil drsining more towards the back of the head because of the angle of the engine being lower in the rear?

vanlieremead

Bore scoring is seen from the bottom and not the top. One has to drop the pan and then borescope. It is often accompanied by clicking only really heard if you place your head in the real wheel well on the side of the suspect cylinder.

What year is your 987.1? If a 2005, then you are most likely ok. If later, could have an issue.

ochristofferson

If you want to fix this without the zip tie, you can get a replacement connector and a tool to swap out the leads. I broke the locking tab and although the weather seal seemed like it would hold, I really didn't want it to stay that way.
The replacement connector is a Bosch connector but has a Porsche PN: 1.928.403.110 You can find this part for about $5 online.
You'll need the special tool to remove the existing wires and then insert those crimped wire into the new coil pack connector. This is a TE CONNECTIVITY/AMP tool with part number 1-1579007-6.
This will cost you anywhere from $65-$106 depending on who you order it from. Newark seemed to have the best price.
The tool makes the swapping of the connector literally a 5 minute job - no soldering, crimping, shrink wrap, etc.
Because each crimped wire lead has 2 ears, a simple, single tool would be considerably more difficult to use.
Yes, a rather expensive solution compared to the zip tie. Your decision.