In need of some help,

I have a 2005 997.1 Carrera 4S, a month ago I went to do a normal fill-up at the petrol station and after filling up I was hit with a CEL and the car was running rough at idle but still able to run. I plugged in durametrics and pulled out the codes and had the following:

P0040 - Oxygen sensors in front of cat conv. Switched
P0300 – Misfiring checksum error
P0301 – Misfiring cylinder 1
P0302 – Misfiring cylinder 2
P0303 – Misfiring cylinder 3
P1371 – Valve lift control checksum error
P1359 – Valve lift control cylinder 1
P1361 – Valve lift control cylinder 2
P1363 – Valve lift control cylinder 3

So far a lot has been done to try and rectify this but unfortunately no success.

Notably this only happens once it reaches 90+ on the oil temp reading, before that the car will run normal.

Petrol tank has been emptied and filled a few times but hasn’t made any difference to the problem (I suspected bad fuel at first).

After erasing the codes the first time the only codes to come back out are the first 5 and not the 4 following. If the car is running with the CEL and the codes are erased the car will run smoothly again, same with if the car is switched off and then started again it will run smoothly. If you drive the car with the CEL it will also go away and the car runs perfect, it only happens when the car is sat in start/stop traffic or at idle.

Spark plugs have been changed, coils were changed in 2014 but tried swapping them to opposing banks but the fault codes still appeared the same. Also tried a new set of coils in the car and still the same problem. The bank 1-oxygen sensors have been replaced, also hasn’t resolved the problem. Any suggestion on what else needs to be checked?

I have been through many forums searching for an answer, many people have had similar codes and symptoms but until now I can’t seem to find a definitive answer to what the solution is to the problem.

Any help will be appreciated, hopefully to avoid spending more money on parts that don’t solve the problem at hand.

 

Reads like there's a problem with the valve lift on the #1 bank.

Do you hear any what sounds like lifter ticking concurrent with or shortly after the CEL come on?

A section of my 996 Turbo's DME OBD2 manual covers misfires and misfires possibly caused by a bum VarioCam Plus problem with the low/high lift lifter system.

I have a PDF of this I can email you. It is about 639Kb in size. While it is for the Turbo, there are some similarities and it might prove of some value.

The odds are you are going to have to take the car to a shop with sufficient knowledge/experience which has access to the VarioCam Plus test steps specifically for your car so the correct diagnosis can be made and the source of the problem corrected.

If it is the VarioCam Plus system the intake lifters on the #1 bank will probably have to be replaced. But let a professional Porsche tech make the correct diagnosis and tell you that.

I'd avoid running the engine any. It won't get any better with more run time.

Send me a private email if you want the above document and be sure the email inbox can accept the PDF.