Petza914

With a motor that holds 10 qts of oil, revving the engine to over 4,000 in the first minute, before the oil is warmed up and flowing well, is a great way to potentially throw a rod or score a cylinder. I'd recommend not doing that particular test anymore. Revs should be kept to 3,000 or below until the oil is up close to 200 degrees F mark.

gronkX

It's more of a quick blip over 4k while in neutral - I try not to drive it hard until it's had a bit of a chance to warm up.

gronkX

I'm still looking for some suggestions.

Quick recap:

- Purchased the car a couple of months ago
- as part of PPI, the plugs were pulled to check out the cylinders, and new plugs were put back in
- since then, on some but not all cold starts, I get 0300 random misfire, plus usually between 2-5 individual cylinders. This always happens around 60s after startup.
- the CEL did not occur prior to changing the plugs.
- I've done some additional testing, and discovered two things:
- if I blip the throttle to get revs over around 4k, even for a second or two, the CEL doesn't happen
- if I hit the sport button right after starting up, I do not get the CEL.

Do I replace the plugs and coil packs? MAF? Or could there be something else going on?

The car drives fine otherwise.

Monster231

Did you try cleaning or replacing the MAF yet? how many miles on the car? Seems like the obvious & easy next step. Even if it's not the culprit, your still probably replacing a 13-year-old part

gronkX

Cleaning the MAF is on the list. Car has 115km on it.

Z00mie

Same type of issue on a 2006 C2S, with 52K. On initial cold start rough running, CEL illuminates. When I look at Durametric data, misfires on 4-5-6 and a second code (which I cant remember). If I shut the engine down immediately and restart the engine runs normally.
I've added some fuel therapy lately, Gumout Regain, high mileage additive after reading Bob's The Oil Guy threads. Anecdotal but, my car runs smoother and hasn't since popped a code. My car also has the slow cranking issue (even with new battery) which I attribute to the bad Positive Battery Cable issue that hasn't yet been addressed in my car. I suspect that could also be contributing to the CEL issue.
Maybe the initial start electrical load is too much and the variocam system is the 'last to get a drink at the electrical trough' and/or just bad/stale fuel?

It only has done this a total of 3-4 times in the car's life...

gronkX

Update: Changed the spark plugs and coils, but did not touch the MAF yet.

Result is the same: Random misfires around 60s after the car is started, but only when the engine is cold.

Next step will be to clean the MAF.

Euro RAE

I am having this exact issue on my 997.1. As the OP stated my issue started after installing new plugs the other month. During cold startup the car starts and idles fine for the first minute or so, then it will start to idle rough and throw various cylinder misfire codes. If I cut the car off and right back on the car will then idle perfect. I have replaced the following; all plugs (Bosch), all coil packs (updated Bosch), all O2 sensors (Bosch). After reading this forum and others I cleaned the MAF sensor (looked brand new) today with some CRC cleaner, no change. Aside from this cold start misfire issue the car runs amazing. In fact with these new parts and my recent mods it has never ran better. Cold startup after a minute or so very rough idle, CEL with various cylinder misfires codes. Applying some light throttle cannot balance the rough idle out either. If I just continue to drive it drives rough. However cut the car off and right back on and she purrs like a perfectly tuned machine?!? In another post about this same issue someone mentioned lifters and/or injectors, but I can't see that being it runs perfect after warm startup. Another post mentioned the hydraulic lift solenoids, could that be it? I believe this has to be a sensor or part only utilized in the air/fuel/spark control during cold startups as all other times it runs perfectly. If anyone else has any thoughts on this issue I would love to hear them.

Petza914

If all of your misfires are on a single bank, it's the cam position (hall) sensor on that side - mine did the exact same thing and that fixed it. If on both banks, could be the crank position sensor, an intake leak or something else.

Do you have a Porsche scan tool that will let you see camshaft deviation readings on both banks. If one is showing 0s that's the bad one.

The reason this happens is that the car ignores that info during the warm up so it runs normally but then when it switches over to intelligent mode and it doesn't get any data from one of the sensors, it starts running badly.

Euro RAE

Thanks Petza914! I don't have a Porsche scan tool, although I should just go ahead and purchase a Durametric already. I do have an OBDLink tool and thus far every time I've scanned it was cylinder 1, 2, and/or 3 showing the misfire so indeed all on the same bank. Based on your advice and similar issue I will definitely check out the cam position (hall) sensor for that bank and report back.

Petza914

Here's what mine looked like when it went bad

Euro RAE

Super helpful and much appreciated! I just ordered two camshaft position sensors from FCP Euro (Bosch 0232103057) for $28.89 each. Figured might as well go ahead and replace both of them. A Durametric is certainly next on my list too. Will advise once they are replaced.

Petza914

I would just replace the Bank 1 side and keep the other as a spare, but your call. IMO, no point in replacing something that's working, as the new one has a small chance of being bad or failing prematurely. If at some point you start seeing the same thing on Bank 2, you'll know the culprit and what the repair takes.

Attached is a document from Pelican parts that shows the position of all the engine sensors.

Euro RAE

Doh, well add new camshaft position sensors to the list of not it parts. Going to take it to the dealer and see if they can offer a clearer solution as I am at a loss now. Still only misfires on cold start up, bank 1.

Petza914

Bummer. Before changing them, did you get a scan tool and see what values you were getting from the CPSs?

I don't recall...did you change the MAF. The temperature sensor is integrated into the MAF and if you're not getting an accurate cold start temperature reading, the car won't enrich the mixture during that time, and you might get misfires, but when warm, it would run better with normal fueling.

Another test would be to start it and then disconnect the plug to the MAF and see if it gets better, worse, or is exactly the same. The MAF serves two purposes in a normal 997 setup - it provides the air temperature information and the air mass information (by how much energy is required to keep the MAF wire at a certain temperature). The more air going through the MAF cooling the wire, the more energy is needed to maintain the wire temperature. These are separate wires on the MAF plug.

A temperature sensor test would be, when you first start the car after it sitting and cooling all the way down, do you get the elevated idle that should happen that eventually cycles down to the normal idle RPM. If you do, then the MAF knows the car is cold. If you don't then I think the temperature sensor in your MAF may be bad. The coolant temp sensor also reports information to the DME so if not the MAF temp sensor, that might be another one to check.

To do this efficiently though, you really need a scan tool where you can monitor these values instead of throwing possible parts at the issue to see if it fixes it.