My 997.2 C2S has around 1600km on it now and for some time it's had a very minor but irritating hesitation at 1500-2000 rpm.

It mainly happens when you've backed off, say coming into an intersection in 2nd or 3rd, and then ease back on to the throttle. Has anyone else experienced that? It's what I'd call a 1/2 missfire - sort of like the ignition missed one spark and recovered.

It's also got one slightly noisy tappet or injector which you can clearly hear at idle. I'm wondering if this is related, or if this is typical of the DFI engines.

 

I have exactly the same hesitation problem but on a 997S.1 Haven't a clue yet what it is....

 

Thanks Ian - I was wondering if it's a characteristic of the DFI engines related to them going lean on the overrun but if you're getting the same thing maybe not.

My 08 C2 didn't do it.

 

Mee too have that very thin hesitation between 1500 - 2000 RPM when hitting the gaz pedal. Any conclusion on your side?

 

7200 miles on my 997.2 C2S. When the engine is initially cold, there is a definite hesitation. I've "fixed" the problem by waiting 20 secs of so and (maybe) let the high pressure fuel pump stabilize - seems to help. The car sounds like a little like a diesel on start up - not a pretty sound coming from the DFI. Everything smooths out at operating temperature

 

I feel it at around 2800 rpm at partial throttle. I have convinced myself it is the variocam in action.

 

Mine has 4200Km and I don´t have any hesitation at all, it has lots of low end torque available withouth any flaws.

Engine sound at idle while cold is not very refined for such high end sports car, this is proper from every new generation DFI engines, the M5 is even worst. Anyway, it gets better when reaching normal operating temperature.

 

I also have hesitation at that RPM range and have read/heard it is the DFI - I didn't have any hesitation on my 997.1. It is only at partial throttle.

 

The hesitation I was experiencing when opening the throttle at around 2000rpm seems to have been down to lambda sensors. It took a local Porsche specialist with 20 years Porsche motorsport experience and a full factory PIWIS (with full Porsche Technical backup) the best part of 2 hours to find what was happening. No fault codes, just an aged and slightly out-of-calibration sensor.

Replacing both pre-cat lambdas solved the issue.

As an aside, I'm rapidly starting to learn that these cars don't throw fault codes until something very major is wrong. Sensors (especially MAF/Lambdas) can be far enough away from spec to have the car running like a dog, but without throwing a code. Cursory use of the PIWIS just to look for fault codes will not find the majority of issues that can cause the cars to run less then optimally. The PIWIS is capable of reading every conceivable operating parameter in real time, but without someone who REALLY understands engines (mechanically) and the DME systems (in real depth) to interpret what they're seeing, most faults will never be found.

 

[quote=J.Seven;2539979] I don´t have any hesitation at all, it has lots of low end torque available withouth any flaws.

quote]

Ditto .

 

Same here on a 997s.1, just a slight hesistation on low rpms. The hesistation occurs more often when the engine is relatively cold. You guys think this is normal?

 

Try to get MAF sensor out and clean it as a first step. I did it together with plenum install and my low rpms improved - even on idle it started working smoother and without any rattle, also quite noticeable when I have to go 4-7 mph in bad traffic.

 

Thanks for your response, I will keep this in mind.

 

HI aggie,
i have that tappet noise at idle u are talking about.
not a big deal but

 

I am told that "tappet noise" is really the DFI engine's high pressure fuel being injected into the cylinder-head (unique to the new DFI engines).