2009 C2S 2700 RPM Thump / Miss / Hesitation - Solved...

I posted this the other day at Rennlist... thought you may be interested. I suspect I will fuel neurosis for those who have early builds of the new DFI engine or PDK.

Rennlist Thread

2009 C2 S Dec/2008 Build

Well solved is a bit strong but the issue is very much improved along with other interesting changes.

Solution: Re-flash the ECU with Porsche's more modern programming. Perform the "long version".

Problem: I get an odd thump or hesitation under mild load around 2700 RPM. It can happen at lower or higher RPMs depending on load, pedal position etc. It is more pronounced when engine is still cold. It happens in all gears. Does not appear to happen under hard acceleration. No CEL and the Porsche computer recorded no faults.

Suspect: Variocam Plus transition from low to high lift.

Advice from the 'net: Folks who have this symptom have posted that their dealers say it is normal with some cars having it and others not. Some suggested it is a "lazy" solenoid/actuator. My dealer never heard of the issue.. I was the only complainer.

Ford Engineer's Advice: Reflash the ECU. I took my friend who is a 30 year Ford engineer and now in the corporate services side for a ride. He immediately said it was most likely a software issue and have Porsche re-flash the ECU. He said the industry classifies this type of issue as "driveability". This is code for "nothing is wrong but we are going to fix it anyway". He noted Ford, and all car companies, are constantly tweaking the ECU programs/ignition/shifting maps etc. for improved drivability. Think Windows updates. The company may not issue a TSB unless it is a common complaint. If the TSB tells the dealer to reflash the ECU, the customer gets a summation of many many tweaks.

Cost for Flash Update: Zero, the dealer did this for free. While I didn't ask why but did thank them, my Ford friend noted the ECU is considered part of the emission control system and is subject to the fed mandated 5 year warranty, therefore my 2009 is still under that umbrella. I know the guys at my dealer well (scary eh?) and they doubted this flash would fix the issue but did it anyway (I did reproduce it for a tech... he didn't know what it was but thought it was the Variocam Plus transition). The tech said there are two types of re-flash: a short one and a long one. I asked him what the difference was and he said he wasn't sure but he did the long one on my car.

Impact of the Re Flash on thump: In short, it definitely changed the engine behaviour and the transition is now better masked. It is still there and when cold, is more pronounced. I get this as the software can not change the mechanism, but it can change when things occur, retard timing... etc. Before, I would press the gas, the revs would start to climb and if I was in the mid 2000s, I would then get a thump. Now, it appears the transition occurs as I press the gas so it is hidden and less noticeable. Overall I am happy with this... but I am more impressed with... read the next...

Unanticipated Changes: Wow. This surprised me. The darn thing is just smoother. The idle is way smoother. I was not unhappy with it, but it is very different and better. Before the car would shake a bit and wag its butt as I sat in my garage. Now? Smooth as silk. The engine also appears to be more responsive.... such as when I blip the throttle when I downshift. It appears to jump and respond quicker. And here is an odd one.... I think... I think.. I am getting better gas mileage. Before, computer read my average mileage was 18.9. Now after resetting the computer immediately when I picked up the car, after about 5 tank fulls, a variety of highway, dopey city start stop, etc. etc. is says 20.9/21. Will this hold as I drive more? I dunno. Ok, now for the big HP question: no I don't think so. Other minor improvements/changes... when I shut down the car, the engine would jump/jolt a bit. Now it just stops. Look, these things are pretty minor, so it is not like the car was a mess before but there are definitely differences and I like them.

Should you do this?: My car is an early build, Dec/2008 with the new DFI engine, so it stands to reason that earlier cars do not carry the improvements of later cars. My Ford friend noted that cars with a new component, like say PDK, will have more tweaks when new. All I can suggest is that if you have a 2009 and have the thump, get it. It won't make it go away but it will make it less annoying and you get other smooooth improvements.

I hope folks with my issue finds this information useful and I apologize to the dealers who may now have to deal with us neurotic owners.

PS: If you think about it, why should our car's software be any more stable than Windows or Android? Just look at the crazy stuff in the Durametric software that we can control.

Peace
Bruce in Philly

No thumps and barely perceptible at that. At first I thought it was a road irregularity on an uphill about a quarter mile from my house... maybe some of the effect is that anyhow. The motor idles well enough, although sometimes after a full drive the idling engine causes the car to have a slight horizontal shake. The '01 would do that sometimes, too, so I attribute it to a particular circumstance of fuel/air regulation, rpm, and a flat six harmonic of sorts. (Offset crankpins?)

My symptom is definite thump I and others who have it in our '09's attribute to the variocam plus lift transition. So, I have not comment on your issue..... I only play a mechanic on the 'net.... in reality, I am a dog.

You may want to talk to your dealer about this as my Ford friend used "idle when cold" as a common software programming tweak (although I don't know if he was referring to cold weather or just a freshly started engine) along with automatic transmission shifting (another common driveability complaint).

Woof!

Bruce in Philly

I think I brought this up with the dealer months ago, but they allayed my concern. If it gets more obvious before the warranty is up I'll press the issue.

Manufacturers can also use software changes to mitigate the effects of failing/poorly designed hardware.

The variable valve timing on BMWs is called VANOS. In time, the seals on the E39's VANOS hardware deteriorate to the point where there are real drive-ability issues, including a wildly rising and falling idle, to the point of stalling.

For 125 of my hard-earned dollars, the dealer reprogrammed the ECU, which significantly reduced the symptoms of the failing VANOS seals.

Subsequently, I performed the REAL fix - replacing the bad seals with new ones, available from a bright and industrious entrepreneur. [www.beisansystems.com].

BMW would have happily replaced the entire VANOS unit, for major $$$.

Software updates, to fix software problems, are great. Software updates to mask hardware shortcomings... not so much.

I'm not suggesting your problem was a hardware//mechanical problem. As computers become more and more an integral and very significant part of our cars, software fixes can indeed 'fix' the problem.

Lately been paying too much attention to the upshift reminder. That last part Thruway trip to Woodstock left soot on the pipes as GiO noted. Up in this thread I mentioned the sometimes slightly lumpy idle. Also, for quite some time, on quick high rev 1-2 shifts the exhaust would make a sloppy spattering sound, nothing like a PSE or even the standard exhaust should. This trip had a lot of hard accelerations, several to redline, and gears were held one or two down from usual. Well, nearing my destination on stop and go roads there's been no splatter, just a nice burble, especially with the Sport setting. On arrival, the idle seemed smoother, and lo and behold: the exhaust tips are as clean as when I left!

Even Porsches run better after an Italian tune up. Good for the car, good for the soul and good for permagin.

These are, after all, sports cars - designed as sports cars and they're happiest when you drive them as such. I'm sure that things like upshift indicator, Stop/Start are only designed to meet fuel economy standards, not for the good of the car.