Check Engine Light - OBDII code P0306 ***UPDATE***

Hey guys, I need some help. I got the CEL, the other day and stopped by a local shop I use (dealer closed on Sat.) to hook up a OBDII scanner and get the code. It was P0306 - Misfire cylinder#6. They assumed it was just a coil pack so ordered one, and a plug, and changed it for me. Problem is,...that didn't correct the problem!!! They took the parts back off and said it'll need to go to Porsche, as they didn't know enough about these cars and weren't going to waste my time and money. So, anyone "been there..done that" with code P0306 -misfire? It actually still runs pretty normal, just the idle is kinda rough. I've only driven it to/from shop (gingerly) which is about a mile away, though. BTW, the CEL is solid...not blinking.

The connectors on the coils are really tough to go back on. I would bet that the connector just needs to be reinserted so it clicks. This happened to me and the idle was rough too.

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Thanks.....I called the mech. about the connection and he assured me he had it tight and heard/felt the "click". He actually fitted it twice. The coil pack wasn't cracked and no oil was found at pack or plug. The spark plug wires were good and he also checked sensors. That's why he was lost at that point and recommended me just to take it to the dealer. Some reading on Renntech, suggested the same as you. Some other possibilities may be injectors or even an air leak. Those seem to be long shots, as the P030x misfire codes always appear to be coil/plugs. And there is a known history of failures on the coil packs. My car has 41,000 miles. Could it be something major? Anyone?

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If check engine light *not* flashing odds are misfire can't be too bad. This doesn't mean the underlying cause anything to ignore. Niew coil pack new plug didn't fix the symptom. I assume the error code was cleared after new coil/plug installed? You'll need to be able to not only read the error codes but look at OBD II sensor data in real time. For one thing I'd like to know what the long term fuel trims look like. If injector leaking engine controller will go lean on that bank. Another possibility tht can produce a mild misfire error code is a burnt (usually exhaust) valve. A compression test, perhaps a leak down test called for but not before eliminating as many other sources of this symptom as possible. If you take it to a dealer tech can turn off spark/injector to each cylinder in turn and note the effect this has on engine rpm. The weak cylinder will have the least effect on engine rpm cause it contributes the least to the engine's output. Another possibility is cylinder developing a crack around top of cylinder and it is just bad enough to cause misfire but not bad enough to make its presence known. The state of the plug from the suspected cylinder can tell a tech something. And if crack suspected a compression test or leak down test of the engine cylinders is probably called for. You can also have oil analyzed to check for presence of coolant chemicals in oil. Given the possibility of severe engine problems I'm reluctant to advise much self-diagnosis, but one possiblity is if engine continues to behave otherwise is to run a bottle or two of Techron through gas tank -- follow Techron instructions -- to see if fuel injector or valve or combustion chamber deposits accounting for misfire. I like to change oil/filter after using Techron. Regardless of what you do, my advice is if at any time engine's condition worsens -- it exhibits any untoward behavior -- to shut off engine immediately and without ever starting it again have it flat bedded to dealer for more thorough diagnosis. Sincerely, Macster.

Thanks for the reply, Macster. First thing is that the shop did not clear the error codes. Is that important, seeing as the problem is not resolved? They removed the new coil/plug and put the old ones back. Also, I forgot to mention they did check compression, after the coil/plug didn't work, and found no issues there. So, it (hopefully) may be the fuel injector, at this point. I like the idea of running some Techron, to see if it may only be a dirty injector, or something, but hesitate to run the car that many miles with the CEL (although, it's NOT blinking), to get 2 bottles through the system.

The light will stay on even if you fix the problem. You have to erase the code to get the light to go out. If they erased the code/light and then after the new plug/coil pack it came back on thats different. Their discomfort on working on your car should tell you something!!

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If shop replaced coil/plug and expected light to go out on its own stay the heck away from the shop. Never use it again for anything. You need to find a shop that knows what it is doing. When in doubt you can just take car to dealer and ask the #6 coil pack/plug be replaced. Unless other plugs new though you might to replace all other plugs. Ask before you turn over car if the error code can be erased. Get it in writing and be sure the erasure noted on the receipt you get after the job done. After coil/plug(s) replaced and error codes erased drive the car and see what turns up. You can still do the Techron thing if you want. Unless the car driven regularly chances are it has some deposits. If car driven regulary you might skip the Techron treatment. Up to you. I was able to view a Boxster engine head disassembled on work bench at local dealer the day. An intake valve spring broke. Anyhow, looking at combustion chambers and was amazed at how little build up in the combustion chamber there was. Upstream of chambers intake valves were clean too. Asked tech about the car and he told me the car has around 65K miles on it, owned by a woman, and she drives the car daily. She also takes care of car. Sincerely, Macster.

I should clarify....the error code (P0360) WAS cleared after the coil/plug replacement. It's just that CEL came back on, and they received the same error code. At that point, they realized it was more than just an easy coil/plug replacement. They did check the compression, for me (which was fine) and stated perhaps it was an injector issue, but didn't want to begin speculating and called me suggesting I just "flatbed" it to the dealership. Upon arrival to pick it up, I started it and the CEL was NOT blinking. It had the same rough idle, but figured I could drive it home, which is only a mile away. He did asked me at that point, if I wanted the error code cleared, to come back and he'd take care of it. I assumed his thoughts (as were mine) were to leave it on, for the dealership, if it were to be towed. I do want to say that both the shop and I were in agreement that a qualified shop or the dealer would be the best idea, for this car. I've known these guys for awhile, and they've always worked on my domestic vehicles. It was simply that I went to them to use their OBD-II reader, and when the code indicated misfire, neither of us felt apprehension for doing a coil/plug change out. It's just that I wasn't that lucky, on this one!

5 bucks they replaced the pack on the wrong cylinder

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Error code was P0306 = cylinder #6 They replaced the forward most (i.e., towards the front of the car/back of engine) on the passenger side. Is that not the #6 cylinder?

Hey guys, just to follow-up on the CEL/Misfire I had,....it turned out to be a stuck lifter on Cylinder #6. The mech. did state that the oil looked a little dirty. I found this strange as I know the oil wasn't that old (don't have the exact mileage, in front of me). Anyway, it got a oil/filter change while there. Mech went with the Porsche recommended 0-40 Mobil 1. He stated the trouble with lifters was the main driver behind Porsche's switch to the lighter weight oil. Anyway, a whole lot more $, than a coilpack.....but at least she's purring like a kitten again!!! So, heed those CEL's,....you never know!

Thanks for the update. Hopefully that will help someone else in the future. I can't wait until a certain "someone" reads about the use of 0-w40 (a.k.a. "Mobile water"). It should be fun!

I had that same issue about a year ago. They replaced a lifter under my CPO.

Did you have 0-40 in the car when the CEL went off? What did you put in there now? I had P0301 blinking on my car after a spark plug change. It flashed twice I shut off the car right away. Started it up again,CEL was solid. Stupid Coil Pakwas loose. It was making a clicking sound even thought it wasn't seated right. Funny thing when I took everything apart again,and actually lifted the little sleeve/cover and watched it seat on the ignition coil it didn't make a sound. Cleared the CEL started it back up and was good to go.

just a fyi before you just replace the coil pack you (or a good tech) should switch the suspect pack to another cyl and see if the code follows. no use buying a part that you might not need.

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I dont want to lose it.