Recent posts concerning misfires once again leave me scratching my head concerning my '09 C2S. Since new it has exhibited a slight "misfire" when passing through approximately 2600 rpm. At times the misfire is barely noticeable, but at other times it is fairly pronounced. As it only happens when accelerating through this rpm range I am lead to believe it is not ignition related, which leaves the variocam as the prime suspect in my mind. Took a drive with a dealer tech and the diagnostic computer hooked up, but it threw no codes. Tech also said that the minor "misfire" was normal, and of course "they all do that". I am trying to determine if the variocam system is capable of being adjusted to eliminate this problem.

 

I have a 2008 BMW 535 with DI and my car has had occasional "misfires" since new. The car now has 45,000 miles. Actually, I believe these are not ignition misfires but actually fuel injector misfires. It can happen at idle, while accelerating or while cruising. No faults are recorded for the dealer to notice. You indicate that it only happens when passing through approx. 2600rpm so perhaps it is the valve timing or lift changing modes.

 

Do we know what triggers engagement of the more aggressive variocam profile? Is it based purely on RPM?

 

Here's a link to Porsche's info. Doesn't go into any significant detail though.
http://www.porsche.com/microsite/tec...lectedVariant=

 

runner1021,
Check out the thread "Fuel pump failure 3800 miles". Your stumbling at 2600 RPM might be related to a fuel pump issue. A couple owners seemed to experience this before the common 2009 DFI fuel pump failure.

 

i had misfires in 3cyl when i was in trip.then i changed all plugs ,coils and the problem remained only in startup!
then i changed variocam sensor (the car has two in each block for low and high rpms).
finally was the variocam sensor of one block in high rpms!

 

I had a similar issue with one of my vehicles, the problem ended up being spark related - it simply ran too rich in this power band and the spark didn't work. Changing plug leads and working on the tune-up, running slightly leaner, fixed the issue.
This may be completely different, but I know the hesitation as you accelerate, its the same thing, and it always occurred in a certain rev range.

 

Hi, sorry to dig up this old thread.

iliasgk74 - did the problem happens consistently at certain RPM?

To OP - was the cause of the problem for your case related to the fuel pump or variocam?

I'm experiencing this very similar issue, the engine hesitates at about 1200RPM. It usually happens (or more noticeable?) when I press the gas panel harder, and I don't notice this if I press down very gently / slowly. it can happen either when the car is idle or accelerating from stop, no issue when cruising as its above 1200RPM.

 

I think what you are encountering is the VarioCam Plus system transitioning from low lift to high lift. This happens around 1400 rpms which is sort of close to 1200 rpms that you report in your post.

With my 03 Turbo to avoid this -- actually to avoid triggering the low lift switchover -- I keep rpms above 1400 unless I'm getting the car moving from a dead stop. This means among other things this means when I hard accelerate I start from above 1400 rpms.

 

I have the same issue.... I suspect it is with the earliest builds.

I have an appointment with my dealer tomorrow, Tuesday to flash the ecu as I suspect this issue was corrected in software. I will start a post in a few days to inform of my findings.

I have a 2009 C2S with a build date of 12/08. What is your build date? Check the plate on the door under the latch (not the chassis jam, but the door).

My dealer does not believe the ECU flash will fix the problem, but then again, he never heard of anyone complaining about this.

I too believe it is the variocam system. If the flash does not work, I may just replace the actuators myself when I do a spark plug change in a few weeks. The actuators, one for each bank, are located between two spark plugs and can be easily accessed with the exhaust removed as when changing spark plugs. The actuator is about $150 each from Pelican or other Porsche parts suppliers.

I have tons of data on this, check your PM and we can communicate off line. I find this really annoying.

Why do I suspect a software change? I had my friend, a 30 year Ford engineer and now service zone manager and we took a ride. He immediately suggested software and then told me how Ford addresses this stuff. First, if this issue was new to the dealer, they would plug in a device into the OBDII port and let you drive with it for a few days. Then, when you experience the issue, you press a button and the device records engine data for 30 seconds prior and 30 seconds post your press. The dealer then uploads this directly for Ford in Michigan where it is reviewed by engineering. This is their OASIS system. Then, if appropriate, engineers change the programming and the newest builds get the updates. The dealer will then be asked to flash your ECU with the updates. My friend also noted that TSBs may not be issued yet there may be many tweaks to the engine mapping. Therefore, he told me to ask the dealer to reflash the ECU. So.... appointment tomorrow, Tuesday. We will see.

I corresponded with another Porsche indy, who thinks it may be a "lazy actuator" but he recommended collecting engine data (like Ford would do) using the Durametric tool... that I don't have.

Again, check your PMs and we can communicate off line. If there are others out there having this issue with a 2009, PM me and I will build an email list. Please note your model and build date.

Peace
Bruce in Philly