Ahsai

What are the cam deviations, FRA, and RKAT values on both banks?

Macster

Easy one first. When you unplug the MAF the CEL might come on and rather quickly. This is the result of the MAF being unplugged.

Just because the CEL comes on with a code related to the MAF you do not stop there.

If the engine is otherwise not exhibiting any issues you should try to drive the car again like you were driving it before and it manifested the behavior that prompted you to unplug the MAF in the first place.

It is not really a valid use of the MAF unplug test to unplug the MAF because the engine misfires at over 5K RPMs and then after the MAF is unplugged to drive the car around the block and hardly break 2K RPMs.

I note you replaced the plugs and coils.

I'll assume you used the right plugs. (I came upon one owner who used some other brand and style of plug (the center electrode was recessed in the tip ceramic.. don't ask me why I have no idea). I double checked and the plug maker's reference chart had this plug listed as being a replacement for the stock plug. Regardless, the replacement plugs proved to be so bad the owner was going to remove the new plugs and replace them with new stock plugs.)

The coils must be securely connected to not only the plugs but to the engine wiring harness.

When the old coils are removed, one should take note of the coil and its connection to the harness looking for anything out of the ordinary. Similarly when connecting the coil to the harness connector one must ensure the connection is a secure one and there is no risk of the connection coming loose.

Last but not least, IIRC VarioCam kicks in at around 5200 RPMs. The intake valve timing is retarded (which is what I recall reading but seems "wrong" to me).

If the VarioCam system isn't working right this might (I say might) account for the misfires. I was told when the VarioCam solenoid/actuator were bad on my Boxster that one symptom can be misfires as the DME adjusts fueling in an attempt to get the readings from the O2 sensors it expects. Because the VarioCam is not working right it won't and the DME can adjust fueling too far and misfires can result. In monitoring the short term fuel trims I was seeing some weird fueling taking place and told the tech about this -- which prompted him to tell me what I related above. The VarioCam solenoid/actuator failure was at that time though intermittent and the fueling didn't go off the deep end and the engine didn't misfire. In fact it ran rather well.

You can I believe view the cam timing in real time with a Duramatric. If I'm right you could use this tool, well, have a passenger view/log data, while you are driving the car and to see if you can spot anything amiss with the cam timing.

With just an OBD2 scan tool/data viewer you can view short term fuel trims in real time and perhaps spot something out of the ordinary. However, it will be more a stretch to blame the out of the ordinary fuel trim activity on the VarioCam acting up.

Other explanations for misfires can be there is an intake leak,. An AOS generally doesn't cause misfires at high RPMs but I would never rule out an AOS until I have assured myself it is ok.

There can be fuel supply problems or fuel pressure problems.

Is the air filter and intake stock? Or have you gone aftermarket? I bring this up because in some cases some aftermarket filter/air boxes interfere with air flow past/through the MAF and non laminar air flow in the vicinity of the MAF can lead to all sorts of hard to diagnose engine behavior that is ultimately traced to the MAF being affected by unsuitable air flow.

gixxe638

sorry i don't know how to check that. what are you looking for with that info timing problems?

Ahsai

You need Durametric. Since your problem seems to be only on one bank, cam timing is a strong suspect to me at least. Air leak is less of a problem at high rpm. Fuel pressure and delivery rate should also be checked regardless but it should affect both banks if fuel delivery is the problem.
Also, Durametric may retrieve other pending codes that a regular OBDII scanner may not be able to.

If you don't have durametric, at least you can check the short term and long term fuel trims like Macster mentioned.

Macster also raised some good points about MAF and aftermarket air intake but again your problem seems to be on one bank at high rpm...

trendy996

Primary o2 will also cause misfires

gixxe638

with the MAF unpluged i tested the car for miles in the full rpm range it acted the same as before no power over 5200 but no misfire codes just the MAF code
the plugs are stock porsche from the dealer they were bosch super in a white porsche box with the 996 part number from suncoast porsche. the same for the coils they were the updated coils with a 997 part number from suncoast. there are no mufflers on my car so there is easy access. All the coil that came off had small hair line cracks so i thought i had it but no change at all.

As far as the vario cam i don't know much about it or how to test it. any help in that would be appreciated.

The AOS has been upgrated to a porsche motorsports AOS about 3 years ago some custom vent lines had to be done but it all works good. The kit from porsche comes for a boxter with a new vent line that needs to be customized for the 996.

The intake is not stock it's from evolution motorsports it has been on the car for 3 years with no trouble. cleaned and oiled my fillter just befor i went to the track two weeks ago. At the track is were the problem first showed up so that is why i thought the MAF maybe the oil form the fillter got it. so i installed a new MAF from Pelican parts but no change in the car after a lot of test driving.

I'm going to look for intake and vacuum leaks is there any place known to have a problem where i should start.

gixxe638

i think you might be on the right track its never a misfire on 1, 2, and 3 do the cam solenoid good bad often.

Ahsai

However, if the solenoid is bad, it should trip the CEL. One exception is if it's intermittent then you may get a pending code but not the CEL yet. If you're driving for a track session with sustained problem beyond 4.5k rpm, I imagine your CEL would be tripped.

Durametric can show you mifire on each cylinder in real-time and it can also retrieve other codes that a generic OBDII scanner cannot. The hope is those codes will give you more clues.

Without Durametric, you can still try to diagnose it in a generic way such as checking the fuel pressure and deilvery to make sure they are in spec., checking intake air leak after the MAF but as I said before vacuum leak will not make your engine bog down at 4.5k rpm...

gixxe638

thanks for everyone's help let me just put this out there the car has an IPD competition plenum with the 83 millimeter throttle body that has been on there for one season already worked fine. towards the end of last season I started to notice a little break up on top end at the end of the track day.so I believe this problem started intermittently.

gixxe638

can you tell me your experience with the primary o2 sensor. I know my cats are not in the best shape.

XR4Tim

There's another possibility. If your cat on that side is deteriorating, it can (and will) cause misfires on that bank, and prevent revving past a certain point under load as it gets clogged and backs up the exhaust flow.

trendy996

I have had my primary o2s go bad twice. It will act the same way when your cam timing tension fails. I think you can swap primary o2 from bank to bank if you want to see if the bank misfire changes. If not it's most likely your tensioner which is a ~900 part from Porsche

fpena944

For me the solution was so easy yet ended up being difficult to diagnose because of the codes being thrown by the car.

I ended up having a clogged catalytic converter on that bank!

The way my dealer tested this was just disconnecting the cats and going out for a drive. After that the car ran perfectly fine. So I ordered up some a 200 cell x-pipe from Fabspeed and haven't had the issue since.

Unfortunately the repair did cost much more than the $300 I was moaning about in the beginning of the post but the character of my car has changed and if anything it revs more freely so I'm happy again.

Good luck diagnosing yours - it's probably worth looking at those cats and seeing if they are causing your pain as well. It appears cars on the track tend to kill the cats more often than pure street cars so yours might be doing the same thing.

Ahsai

I like this theory as well. I just had my cat broken street driving 35k miles. The cat is fine functionally (the inserts look prestine and not melted) except the element inside has broken off fmo teh canister banging on the postcat sensor creating a horrible rattling noise. Just curious if your cat element failed the same way or physical it's fine just that it's not cleaning up the exhaust. Either case, one should be able to tell by comparing the postcat sensor readings of the two banks.

gixxe638

Thanks for getting back to me i needed to change them anyway i just ordered cats and x pipe i'll let you know if it works.