Bruce In Philly

2009 C2S Coupe approx 30K miles.

Odd, I get a miss when accelerating slightly when the engine is cold. It appears to be around 3200 RPM but I am not sure it is dependent on RPM. No lights.... no other symptoms.

Do misses register in the computer? Any ideas or anything I can check myself? I have an OBD2 reader but I haven't popped in on yet.

Peace
Bruce in Philly

neanicu

It might not necessarily be a miss you're feeling...I've read something here about a hesitation when the engine is cold...Variocam?(described as normal)...can't recall...
OBD2 is not going to help much if no CEL is set,a durametric or Porsche's PIWIS might tell you more.
A very small vacuum leak could lead to the same symptoms.
Check your air filter and make sure it's clean and most importantly,while you're there,pull the Mass Air Flow Sensor and clean it using special MAF cleaner.

vexed

I get it too, cold engine partial throttle. After doing some reading here I believe it is normal.

dbv1

It's not. I get no hesitation at all at 0F when the engine is cold. neanicu's on the money about the possible causes.

anewman

I have experienced the same minor hesitation/miss/skip (what ever you want to call it) this a few times this week during engine warm up. happens for only an instant during acceleration from coasting, with the engine in the range of 2500-3000 rpm. Not sure if it is related to the warming Spring temperatures, bad gas, (possibly the gas stations is switching from winter to summer fuel mixture ???)

CORSASCHNELL

Have you always had this issue or you are getting this hesitation/miss recently? If just recently then there is something wrong.

Bruce In Philly

Sorry it took me so long to respond, I was out of town.

I think it just started happening about 1 month ago.... but I am not sure. The car was new to me in February this year so I may be only now, getting sensitive to it.... or not.

When I was referring to "cold" I was only referring to start up, not cold weather. I did it today when ambient temps were about 67 degrees F.

The hesitation or whatever, happens mostly at a lower RPM than I had posted previously... it appears to happen in the upper two thousands, but does not seem to be at a hard point. It only happens under mild acceleration pressure when cold.

After much forum searhing etc. Some are suggesting that I should clean my MAF... others are saying it is the Variocam doing its thing and is "normal" adding that it is not the same on all cars. This not the same on all cars is a little odd to me, but OK, maybe.

This from a poster here on RennList:

"I had this on my 997.1 and notice it on my 991 C4S which I have had for two weeks. It is very noticeable to me, slightly more when cold.

On my 997.1, I took it to the dealer a few times and they said it was the variable cam adjustment that takes place at around 2,800/2,900 RPMs. The reason I took it in more than once is I couldn't believe it was that noticeable and was convinced it was a defect with the engine, eventually accepting their explanation. I had hoped it would be improved on my 991 but after driving it, I think it is about the same.

I'm a little surprised that Porsche hasn't done a better job with their variable cam system. I accept it as a somewhat weak feature of an otherwise great car."

Link to thread

So, I am going with the Variocam theory although I will pull the MAF and clean it for nothing more than something to do. I have been to very very dusty and dirty places lately so I feel a need to check the airfilters.

Peace
Bruce in Philly

Macster

Before I go on you should consider having the car checked out by an experienced tech. No need to book a time slot you might see if the SM would ok a tech ride with you or drive your car and of course be sure you can reproduce the behavior or tell the tech how to reproduce the behavior.

While I suspect the behavior is normal I'm not at the car.

So, no CEL? No other symptoms?

Have you tried a different brand of gasoline? Premium of course?

In the meantime, my thinking is the VarioCam Plus system is at fault. Under DME control the intake valve timing is advanced/retarded to reduce emissions, meet the torque demands of the driver, and so on.

(Variable -- low or high/full -- valve lift is part of the VarioCam Plus system too but I do not believe valve lift is involved in this case.)

This intake valve timing adjustment is ongoing and as seamless as it can be but it could be you're just driving the car in a such a way that you are encountering this being activated then deactivated.

Thus you might consider just changing how you drive the car a bit.

I mean let us consider this. The car is a high performance sports car. Not too many years ago it would have been considered a supercar.

That Porsche has made it rather well behaved, reliable, clean, fuel efficient, tractable in a wide variety of conditions yet deliver considerable power at high revs just speaks volumes about Porsche's engine develop.

But there's no such thing as free lunch.

You have developed or perhaps a better way of saying it is fallen into a driving style that just brings out the worst in the VariCam Plus system.

If I'm right then a change in your driving style might be the solution.

Nothing dramatic.

I know for instance with my Turbo the valve lift is reduced at low rpms at around 1400 or 1500 rpms. To avoid excessive wear and tear on this hardware I spend as little time at those low rpms a possible.

When I start from a stop I manage to get the car away with just over 1K rpms and then accelerate up to a speed that when I upshift has the rpms above that 1400/1500 area so the low valve lift system doesn't get activated every shift then deactivated when revs climb.

Perhaps you just need to be a bit, just a bit mind, heavier on the gas pedal and run the engine up a bit higher before you upshift.

You can check the air filter of course for being too dirty or having a tear or being installed incorrectly, etc.

You can even clean the MAF. It is is dirty -- it won't be -- the real problem is how it got dirty, not that it is dirty.

You can try a bottle or two of Techron use according to instructions to see if injector/valve/combustion chamber deposits are interfering with proper combustion and causing the symptom you are encountering.

Bruce In Philly

I will talk to a tech. I have an interior part on order and it should be here in a few weeks.... I will stop by then. That time will allow me to make it reproducible... maybe.

Bruce In Philly

Spoke to the tech at my local Porsche dealer today.
He said it is "most likely" the variocam. I think he said the transition is 2200 but will vary higher depending on loading. He then asked if I experience it in 2nd or 3rd gear... not sure why. I rarely experience it in 2nd but do in third.... all doing about the same MPH. I can get it to hesitate going up a hill near where I live so repeatable. I told him that when I am accelerating quickly, as I would be doing if in 2nd gear, I rarely if ever get it. When is 3rd, I am taking my time and can get it to occur.

We didn't go for a ride nor did I book service time.... I need to go back in a week or so to get my windshield replaced from a stone chip/crack... I will talk about it more then.

He suggested I stay in lower gears at low speeds to avoid a noticeable transition. Apparently, he doesn't get complaints about this.... but then again, I am hyper sensitive to any tick or bump outa my cars.
So, as I sit writing this with a few months of experience with this issue, my belief is that is the variocam system in transition. I am not happy about this but I also don't want to spend out of warranty money chasing down a "design feature".

Peace
Bruce

anewman

my car (08 C2S with 60K miles on Odo) does exactly the same thing as defined by Bruce so I am deeming this "as designed". Dealer said they could not reproduce it, and that it is likely variocam at work, and had no concerns what soever.

Misdirection

Interesting discussion. My 09 has a slight shudder with similar parameters as is described above. I always assumed it was a lack of refinement in the new electronic "throttle" system.

CAVU

Has the car had its 4 year major service?

Bruce In Philly

No it has not had a major service.

I got it to do this hesitation thing in 6th gear. I was cruising along quickly.... in the 80s I think, pulled off of the gas (left clutch engaged), drifted to about 70, and accelerated... not hard but smoothly. At around 75MP and 2800 RMP, got the solid shift in engine output.

I think I am going to have to live with this. I am surprised the tech was not getting complaints about this?

Marc: I think you nailed it in that my driving habits are exposing this and therefore must change a bit. Since I am now paying close attention to this, I find I float the RPMs in the 2300 to 3500 quite a bit. Seems that is where I do all my around town driving.

Peace
Bruce in Philly