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Fault Code P0300 - P0301

neilhazel3

neilhazel3

New member
Hi All,

I have a 2001 996 C4, the engine light came on whilst on a short journey and the engine sounded rough so I pulled over and switched off. After a few minutes I started her again and no engine light and she was running OK so took her home. A few trips out after and all was good, I was following a car one day who slowed to turn off so I slowed behind once it was clear put my foot down and the light came on and she was really running bad. I was not too far from home so finally got there. I had previously bought bought a FIXD "basic fault code reader" once I plugged it in the code P0300 came up, I looked that up to be a misfire.
Some car history:
In with Brookspeed at Eastleigh July 2019 where I had a new IMS kit fitted along with a Major service, new water pump and oil/air separator. so I do not expect it to be spark plugs causing the misfire.
October 2020 new coils fitted (all six) still the same problem
Today fitted a new fuel filter still the same problem also took out and cleaned the Mass airflow metre and tested it and that was working OK but still the engine is on running rough and misfiring.

After spending several hours looking on the Web know one seems to say any one solution. I've done the first and basic things in a logical order (I hope)

Can anyone please help with what else it could be. I live on the Isle of Wight so not easy to get to a Porsche garage.
 
Having replaced the spark plugs and coil packs, the only thing I can think of that would affect just one cylinder is the fuel injector on #1.

Here is the diagnostic sheet:

Download
 
Hi Richard,
Thanks for this, I will check our how to access the injectors and replace, this will be a job for my local mechanic "hopefully"
Regards
Neil
 
Hi Neil,
A really interesting thread. I wish you all the best in finding the source of the problem please let us know the outcome.
Thanks
Steve.
 
I had a similar problem on my C4S and eventually opted for a remap which fixed it and also a slight flat spot...happy days !
 
Hi All,
The fault finally put to bed. My local guy cleared the cylinder P0301 fault run the car again and this time it showed up as P0304 cylinder 4 misfire. He carried out all the basic checks he could and when it came to cylinder 4 coil test, low and behold no electrical feed to the coil so he replaced the coil pack connector and she is now all OK

Thank you all for your input.
 
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