Blinking CEL with codes P0300, P0301, P0304

I've had this issue a while ago but resolved after changing sparks and oil, but it has come back for some reason... 2001 996 Cabriolet with ~61K on the odo it was fine this morning going into work...Started engine this afternoon, engine immediately rough idle, with blinking CEL. Was told by Porsche Dealership (master tech) if and when this happens in neutral to increase RPMs for about a minute or so and then turn off engine and restart. Did that a couple of times and engine refresh and idled smoothly again. CEL remained on and lit but no blinky Pulled codes with generic scanner P0300, P0301, P0304 I was told by Porsche Dealership (master tech) that it could be a "sticky" lifters... He said they are very small and could be gummed up etc... Any ideas? Thoughts? Suggestions? Much appreciated, Happy new year! (way to start it out for me with this issue!)

Misfires are often caused by faulty coils. The most common problem is that the coil cracks allowing moisture in affecting the spark/continuity. If the problem is a cracked coil(s) they may act up worse in humid or wet weather, after a carwash, etc. You might want to have a mechanic physically look at the coils. If the problem continues and the same codes appear again and again, I think this points even more strongly to the coils on the cylinder(s) that the codes relate to.

You say:- Was told by Porsche Dealership (master tech) if and when this happens in neutral to increase RPMs for about a minute or so and then turn off engine and restart. Clear the CEL now and it should stay off. I can't imagine 3 coils all cracking at the same time.

I've not much to add beyond what others have said. While the zero lash valve adjusters are "small" you would have to be really really really bad at oil/filter servicing to have these gummed up. And I think the engine would have fallen prey to other problems arising from lack of oil/filter servicing before the lifters got gummed up. Most often coils are at the root cause of misfires. And blinking CEL is a sign of rich misfires which points more towards a spark problem and not a lifter (cylinder filling) problem. Has it turned off colder and damp where you are? Did you leave the car out in the weather? Otherwise "good" coils can act up, cause misfires, when it turns off damp or the car sits out in the rain. Sometimes even a wash with not enough driving afterwards to dry the engine is enough. Unless you have been a real skinflint with the oil/filter services my WAG is the coils are nearing the end of their life. While it is natural to doubt more than one can crack at the same time, they all are exposed to the same elements and can develop cracks over time that can then result in misfires under some conditions. IOWs, simultaneous misfires is not out of the ordinary. My advice would be to consult with a trusted Porsche tech about this. But I have to tell you if he comes back with gummed up lifters as an explanation I would have some doubts about this diagnosis.

Clear the codes and monitor the car before you start replacing coils, then check to see if the misfires are on the cylinders. I had misfires this year after winterising, and it was down to using non oxygenated fuel, once I was back to a few tanks of premium the misfires cleared and never returned

Yes, thanks all for the advice.. Just FYI Hurdigurdiman, it was only TWO cylinders misfiring P0300, P0301, P0304... P0300 is just a generic misfire code the P0301 and P0304 are specific to cylinders 1 & 4 misfire. Also Macster, yes I'm very sensitive to the nature of this engine and religiously change the oil every 5K or sooner (stuck with Mobil 1 0-40 but that's a whole other topic ) So the advice I've got so far most lead to what you are all saying coil packs, sparks or both. So going to do a complete service. Have a few questions if you can all help out See at Pelican Parts and ECS Tuning Coil Packs Choice of: OEM, Beru, Hamburg Technic and TPI Spark Plugs Choice of: OEM(Bosch), Bosch, Beru, & NGK Too many choices, just want to go with most reliable and cost effective. Suggestions please? Also, should I replace the sparkplug tubes(and O Rings) while I'm there?

I cant speak to the brand of coil to use. I just purchased the Bosch spark plugs for my Cayman and they were the exact same plug that was in there from the factory. I personally believe that if they are "OEM" they are fine (plugs and coils both). Others prefer that the parts come in Porsche labeled boxes because there is no uncertainty as to the suitability or quality.

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Both of my cars have had plugs changed more than once. In all cases I use, have the tech use, what the parts manager shoves over the counter. IIRC in all cases these were Beru brand plugs. In the case of the Boxster I once let the plugs go nearly 100K miles and while the tips were eroded the plugs were working just fine. I would not recommend one let the plugs go past their change by miles or time, but I'm just saying the factory plugs have considerable margin. I can't imagine any other plug bringing any more to the table. With the Turbo the plugs get changed more often. This is typical of turbo-charged engines as these engines are harder on plugs. So far neither engine has required new coils, but both are getting close, and in fact next time I have the plugs changed for either engine new coils will be installed. In short, my recommendation is to just stick with OE plugs and coils. I get a 15% PCA membership discount on parts which helps cut the cost of using OE parts.

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Beru = OEM for coils Personally I prefer NGK as it seems to run smoother. This is based on my experience running both Yes def replace tubes/o-rings while you're in there. I rolled the dice myself and bought 2 tubes only to use if any came out cracked. I ended up only needing to install new o-rings only in my case as the tubes looked new still.

I replaced my plugs and coil packs with Bosch last year. No issues and I'm pretty sure there was an improvement in performance (most likely because my old coils were done). I bought a kit from ECS Tuning that included both plugs and coils at a great price.

Hamburg Technik is a company based in Germany BUT sell chineese knock off parts. Be very careful as they makes you think you are buying German made parts. I don't beleive in changing spark plugs based only on age. Mackster does but I don't.

Since I have a misfire and Cylinder 1 & 4 and have to get to both sides.. It just makes sense to replace sparks and coils since Ill be doing the work to get in there to look at 1 & 4. I ordered the OEM Bosch plugs and OEM Beru coils. Since I've never replaced coils and sparks were replaced about a year or so ago (currently 60K on the OD) I also bought a few replacement spark plug tubes, only to replaced if I see signs of oil seepage. I heard the tubes are a PIA to take out and put in (along with the whole replacement of plugs and coils)

FWIW I actually enjoyed replacing my plugs and coils. Getting the exhaust out takes a while but it is pretty straightforward. The rest of the job is relatively easy especially if you aren't in a hurry. The best part of the experience was driving the car afterwards since it ran noticeably stronger. At least I'm pretty sure it did :-) I didn't have tubes to deal with on my 02 though.

No need to remove the exhaust when changing the coils and sparkplugs. At least on 3.4l

In either case the service is still a PIA but results are clearly noticeable and clears up the misfiring and codes

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+996 No need to remove mufflers on a 3.6 either. I did mine about 3 weeks ago with just removing the headers.

+996 +997, I've done them on both and can verify without a doubt no need to undo any exhaust. It is fiddly work to say the least and is something that cannot be rushed. Just make sure you have the correct size (length) socket extensions, wobbles etc to get into the spark cylinders tight weird angles. Other than that, have a good supply of beer, music and buddy to hang with.