need a 993

Just wanted to go for a ride yesterday to start Father's Day off right when I got the check engine sign. Car started, idled and ran perfectly and still does.

I hooked up my scanner which spat out the code P0306: Cylinder 6 misfire detected.

I'd love to be to diagnose this further but am at a loss. Before I just take it to the dealer, what can I do to diagnose the problem myself.

Thanks from a budding DIYer!

OH yeah, the car is an 03 X50 with 15K miles on it if it matters

Macster

Did you wash the car shortly before you took it out for a drive?

With a misfire there's not much you can do to diagnose the problem. When my 03 misfired upon startup -- once after sitting out in the rain overnight and another time sitting out overnight in the cold damp fog -- I read the codes and talked to a tech and he advised me to clear the codes and see if they come back. I did as he advised and the codes did not reappear. I have let the car sit out a few times since in what passes for rain hereabouts and the engine has not misfired.

So my advice would be now that you've read the codes write them down then clear them and see if they come back as you drive the car as you normally would. However, you should let your favorite tech tell you this, if this is his opinion of course, of what you should do.

As for the cause.... well, with just 15K miles in all this time you do not drive the car very much and I have to wonder if you're going through gasoline fast enough. If not then the gasoline that remains in the tank gets stale.

Also, while probably not a direct factor in the misfires be aware that plugs are due to be changed on time as well as miles. Have the plugs ever been changed?

If the answer is no there is the possibility that with no plug change the coil electrical contacts -- specifically at the wiring harness -- have developed a bit of surface corrosion and this is letting one weak coil cause the misfire.

But like I touched upon above, check with your favorite tech and listen to what he has to say.

tvurt

Clear the misfire, and if it comes back, change the coils and plugs. Easy DIY on jack stands. Just count on a 4+ hours if this is your first time.

Tom

"02996ttx50

probably cracked a coil, from never having been driven.

need a 993

Thanks Macster. You may be on to something. I washed the car Saturday and then didn't take it out for a drive until Sunday morning. Atleast I hope that's all it is. Since the car runs absolutely perfectly, I am inclined to simply clear the code and see if it recurs. But your advice makes sense and I will first check with the head tech at my local Porsche dealership.

As far as driving the car, I bought it 3 years ago with 2100 miles on it so I've averaged about 4K miles a year. So while it's not much, it does get driven regularly.

Will post with a follow up.

SimonK

I have it too. It happens randomly about twice a year. If I un-hook the battery & wait 10 seconds then reconect the battery the fault clears. I changed coils and plugs and was excited as one of my coils had a crack and thought that was it. Noup it wasn't. Got it again! People have this light and it spews out different codes for differnt people. I gave up. I think if I get it twice a year and simple battery reset cures it, it can't be serious enough, so I have been living with it for the past 4 years and will continue to live with it for some more years, I bet...

Macster

I'll bet the misfire is not as random as you think it is. I suspect in your car's case it is tied to something climatic in nature. A particularly sudden change in the weather, going from say mild to cool, foggy and damp, or even a bit of rain.

It doesn't have to be much. My 02 Boxster never misfired a day in its life (now with over 268K miles on its *original* coils). I started the engine and moved the car maybe 50 feet to park it under a carport. Then I left for a week in the other car. When I got back and started the Boxster the engine misfired. The weather turned from nice and sunny to cool and cloudy the time I was gone. The misfire never returned even though the car now sits outside rain or shine.

SimonK

Actually you might be right about climatic in nature. Come to think of it, it does seem to occur when the weather changes. Why do you think resetting battery fixes it? It must be a sensor? MAF? Electronics? Nobody seems to have found a definitive fix...

tomofva

How much to plugs and coils runs and where is a good place to get them?

Macster

Resetting the battery? Perhaps you mean resetting the DME by temporarily disconnecting the battery?

This does not fix the problem. It simply erases the misfire error codes. If the misfires are due to climatic conditions they are almost certainly very short-lived misfires.

As soon as the misfires occur they stop.

The cause of the misfire whether it arises from climatic conditions or not is due to some marginal component, most likely a coil, but if it is a marginal coil it is barely marginal unless the misfires occur too often. One method I use to determine if something like this happens too often is when it happens *if* I can remember when it happened before. But use your judgement and that of your trusted mechanic.

In the case of your car, if the misfires start happening more often and it is from the same coil it might be time to replace the offending coil though I'd advise you to replace all coils on that one bank.

At least.

However, I could justify advising you to replace all 6 coils. (Unless I just replaced the coils and a new one acted up I'd replace all 6 coils.) I wouldn't fool with just one "bad" coil not even just a bank of suspected bad coils.

One justification for replacing all 6 coils is all 6 coils get installed at the same time, they all get removed and replaced at the same time.

SimonK

Ha ha ha resetting the battery? What I meant was indeed disconnecting and resetting DME.

I replaced all coils and all plugs. Fault remains. That's not it in my case.

need a 993

OP here with follow up to original post:

I think Macster was right. I spoke to the shop foreman at my local Porsche dealership who ok'd me clearing the code. It never came back. Looks like it was related to the car wash. Never actually had any problems with the car- always ran perfect.

SimonK

Does disconnecting the battery clears the code? Permanently? Or just temporarily?

wross996tt

Disconnecting for some time will clear the codes permanently. If the fault is still present the codes will return

SimonK

Hey Wross I see we are jumping forwards and backwards from forum to forum? :-).

When you say some time? How long is this. 10 seconds clears it or go for longer. Is there a difference?