Intermittent Misfire

[JayG]

My Targa is throwing a P305 intermittently

I swapped out the coil pack and still get a MIL intermittently. It seems to happen more often at low /idle RPM.
It does clear from the dash if I click Ok with the stalk, which it did not do before I changed the coil pack. It also threw the code more frequently before I changed the coil pack.

I am pretty sure the plugs have never been changed ( I bought the car with 80k on it), and there is 112k on the clock. I was thinking that maybe from the misfire, the plug got fouled a little and driving with the plug firing cleaned it a bit

Any ideas?

[DBJoe996]

Not to be snarky, but, 112K on coil packs and spark plugs? And you wonder why you have an intermittent misfire? C'mon, time to change all coil packs and spark plugs. Just saying....

[32wildbilly]

My Targa is throwing a P305 intermittently

I swapped out the coil pack and still get a MIL intermittently. It seems to happen more often at low /idle RPM.
It does clear from the dash if I click Ok with the stalk, which it did not do before I changed the coil pack. It also threw the code more frequently before I changed the coil pack.

I am pretty sure the plugs have never been changed ( I bought the car with 80k on it), and there is 112k on the clock. I was thinking that maybe from the misfire, the plug got fouled a little and driving with the plug firing cleaned it a bit

Any ideas?

I would do coils and plugs paying close attention to the condition of all. While the plugs are out I would do a boroscope through the plug hole with the piston at bottom of the cylinder. Not to spread fear, but my issues began in a similar nature. Cylinders 5&6. Coils were cracked-plugs were fouled but not because the coils were cracked...

[02TX996Cab]

Give it the old "Italian tune-up" (i.e. drive it in a spirited manner, wind the engine out, etc.) and see if the intermittent misfire disappears. If that doesn't work, then yeah, new plugs and coil packs for all 6 cylinders.

A good thrash on the Three Twisted Sisters (FMs 335, 336 and 337 in the Hill Country south of Boerne) may be just what your car needs. They are reasonably close to you and are an absolute blast to drive. There are decent lunch joints in Leakey and Rocksprings, both of which are on this route.

An engine guru Billy and I both know and trust tells us the engines stay much happier when driven often and hard.

[32wildbilly]

An engine guru Billy and I both know and trust tells us the engines stay much happier when driven often and hard.

That reminds me I need to go do that today. Although everything around here is flat and straight...

[JayG]

UPDATE

It appears the misfire happens at idle/low rpm only

I have a code reader attached while driving and I am getting a P305 code sometimes but no check engine light on the dash

Haven't had a chance to check/change the spark plug

[5chn3ll]

The RennTech and other threads I’ve read definitely point to plugs/coils for the issue. Give the mileage, plugs seems like a cheap “throw parts at it” Hail Mary, so I’d do that and see what happens.

[02TX996Cab]

IIRC, Porsche recommends new plugs every four years. If you do the work yourself the cost is quite modest (6 plugs plus many beers, changing 996 plugs is a PITA). If you have a shop do the work they'll probably charge a couple of hours of labor plus their marked-up price for the plugs.

Changing coil packs is the opposite story; the parts are expensive but they're rather quick to change out (not a PITA). When I last changed out coil packs my Indy recommended using the 997 packs as they are more robust. I did this and have had zero issues.

[JayG]

I have ordered new plugs

Its PITA for cylinders 3 & 4

[5chn3ll]

Ain't gonna lie - I ordered coils and plugs for my 996 a few years back...got under the car...and took it back off the stands and made an appointment with my indy, who graciously agreed to install the parts I bought.