Engine misfire - again but different cylinder

[Hanseman]

Dear Renntech forum,

With regard to my 996C2MY99, I recently had a engine misfire code for Cylinder 5 (with irradic blinking and then steady CEL, indicating cat damage) upon cold-start and ver short drive. However, after reading/clearing the code using Durametric the car did not report anything again for a month. I did replace the oil (no traces of coolant), spark plugs (and the coils looked good) and changed the coolant lid to the latest .02 version. Car ran good for quite some time when suddenly it has steady CEL indicating secondary air injector failure (signal implausible) although I can clearly hear the sound of the air pump running for 30s or so. Deem my surprise now that suddenly the CEL comes on again and then blinks and indicating Cylinder 1 misfire. Any suggestions as what to do? Should I replace ALL the spark coils if the CEL comes on again. Interestingly, this happens after cold-start again and just after refilling gas (which it was the first time also).

Best regards,

Hans

PS. As for changing the spark plugs: working my way by removing the rear bumper, and the exhaust system it was easy to reach all of them, just as indicated by this forum. Although the bolts on the exhaust clamps were rusted so I had to cut them of and replace with new wagon bolts. DS

[Loren]

Do you remember the fault codes from before and now?

[Hanseman]

Dear Loren @ Renntech,

The fault codes were now P0300, P0301, P1319, P1313 and before I had P1319, P1318, P0300 and P0305. Any help is good help...

Best regards,

Hans

[Loren]

P0301 Misfire, Cylinder 1, Damaging to Catalytic Converter

P0305 Misfire, Cylinder 5, Damaging to Catalytic Converter

P1313 Misfire, Cylinder 1, Emission Relevant

P1319 Misfire, Emission Relevant

Most likely causes:

- Fouled, faulty or incorrect

- Contact resistance

- Loose contacts

Have you changed the spark plugs recently?

Correct spark plugs?

Check for cracked ignition coils.

You should check the continuity of the flywheel sensor.

[Hanseman]

Dear Loren @ Renntech,

Thanks for your reply. Yes, I have replaced the spark plugs with Beru having 4 contacts (Porsche original). While doing that I did check all the spark coils for cracks and general abraision but they looked to be in good order. The coil contacts looked good and clean as well but perhaps I should spray them with Deoxit for better conductivity. However, how do I check the continuity of the flywheel sensor?

In addition, I ran the car and looked at sensor values using Durametric software and it seems that one cylinder row has a little higher values for O2 sensing...I belive it was 1.17-1.19 whereas the other side had 1.0 on idle. But values became near (if not actually) identical at 2000-4000rpm. Something related to the variocam gave a value of -2 to -3 o.

Best regards,

Hans

[Loren]

I would double check the coil packs and make sure there is not a crack in cyl 1 and 5. Also, double check the connector on the coil packs - these are easy to not get a tight seal.

The flywheel sensor is a little more of a remote possibility but you can unplug the sensor and measure the resistance across it.

[wross996TT]

My guess is coil packs cracked...

[Hanseman]

Dear Renntech,

Thanks for your advice. I'll drive the car to see if the CEL comes on again. If so, I'll replace the coil on that particular cylinder (1) since I actually have bought one for that purpose. Also, I'll put contact cleaner (DeoxIT) on the connectors.

However, I have the issue also with the secondary air injector which means that I have to replace a valve apparently. Don't know if they are connected but since the error occurs when it is cold/moist in the air on cold-start it is yet possible.

Thanks again for your suggestions,

Hans