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Discussion Starter · #1 ·
I have a stock 09' Cayman S which runs rough at lower RPM ranges. I am unsure if this is a problem or inherent in the engine.

1: Car runs smooth at light throttle at all RPM and has no CEL or pending codes
2: Under mild throttle (4-6 gear), a roughness in the engine is felt at 1700- 2600 RPM
3: Under high throttle (4-6 gear), a roughness in the engine is felt at 1700- 2600 RPM sometimes severe enough to buck the engine requiring a release of the throttle.
4: Using a Bluetooth/Android OBDLink tool: under full throttle, Long term fuel trim -5% bank1, -7% bank2, Short term fuel trim -4% bank1, -5% bank2.
5: The Rear O2 sensors on both banks stay at .6-.7 under any steady state condition
6: Under a transient, The rear O2 sensor on bank 1 sometimes lags recovering from low voltage to the proper .7V by 2 seconds compared to bank 2
7: Both upstream sensors (wide band, I think), have similar readings under all conditions.
8: A small # of misfires: cyl #1 typically has 1 to 2; cyl 2&5&6 - none ever; cyl 3&4 typically 1
9: Cat temps on bank 1 and 2 are within 10 deg under all conditions

I seems like the roughness continues through all RPM ranges, but at high RPM it does have good power. I am unsure if it is the proper power at high RPM as I have only had the car for a few months but it has run great for a couple of track days (much faster than my '69).
The spark plugs were supposedly changed 10K miles ago; I cleaned the MAF sensor and changed air filter. I don't want to just change parts unless they are determined to be bad, but have considered changing 4 o2 sensors coils and plugs or changing the MAF sensor.

I would assume the car should be smooth under these conditions, but do find complaints online of low rpm roughness for DFI engines especially in 981 and 997.2.

Any suggestions or comments?

Thanks
 

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What is the maintenance history on the car? I believe the 2009 DFI cars had issues with DFI pump. Your dealer ought to be able to tell you what warranty repairs were done on to the car by its VIN.

Are you getting any codes thrown? Sometimes the coil packs develop cracks.
 

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What octane and age of fuel in the tank?


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Discussion Starter · #4 ·
No codes.

I was hoping someone would know if the above diagnostic information is within the desirable ranges (not just a range which does not throw a CEL) and if smooth operation at all RPM should be expected. I have also never used ODB data for diagnostics.
 

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Not a Porsche tech so I can't help with the ranges, but it should be smooth at all speed, except, maybe, when under full throttle at too low RPM or because timing is backed off due to pre-ignition possibly caused by poor or old fuel. Used to happen on my 73 when it wasn't driven enough.
Sorry if this doesn't help.


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Discussion Starter · #6 ·
I have put a few thousand miles on the car and refill every week or two with 93 octane, so old gas is not a problem.
It is not a problem is normal driving as the general practice is to keep it in higher RPM at anything greater than light throttle.
 

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the fuel trim difference is normal.
missfires on the cylinders should be 0.
MAF cleaning is a good idea.
you can try to switch coils (or also plugs) between "good" and "bad" cylinders to see if it is a coil thing...
 

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Discussion Starter · #8 ·
The total fuel trim bothered me(short+long); -9 and -12

I found the intake air temp is reading +25degF too high according to my Android app(if the app converts the data correctly). If this is correct, I will change the MAF. Does anyone have the specs to measure the pins directly on the MAF for intake temp sensor?

Has anyone use ODBlink on a 987.2 and measured the intake Temp? If so, is it accurate?

If that checks out, I will swap some coils.

Thanks for all suggestions.
 

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for stock intake the IAT is easily 25-30 degr C more than ambient.
with debaffle and free flow filter i see 12-15 degr over ambient.
All numbers are from OBD reader.
 

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Discussion Starter · #10 ·
for stock intake the IAT is easily 25-30 degr C more than ambient.
with debaffle and free flow filter i see 12-15 degr over ambient.
All numbers are from OBD reader.
My measurement was car cold and not started after sitting overnight. The Intake temp didn't match ambient with a difference of +25 deg. Hot, I had a difference of of +40 to +50 deg.
Which ODB reader did you use? Have you ever taken a cold measurement? If so, did it match ambient?

Thanks
 

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On a hot engine sitting in the traffic 40 degr difference is possible.
I'm always talking Celsius :rolleyes:

Never paid attention at the cold start from the overnight...

I use Ultragauge.
In the past have used Scangauge and bluetooth module+Torque app.
 

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Discussion Starter · #12 ·
I cleaned the MAF thoroughly and the car runs better with lower intake temps reported. The MAF flow rate G/sec at idle dropped from 6.5 to 4.6 and the absolute value of the sum of (short + long) fuel trim is significantly reduced.
 
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good to hear.
did the misfires disappear too?
 

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Discussion Starter · #14 ·
good to hear.
did the misfires disappear too?
The misfires went down to 1, but that during the relearning time frame of the MAF. Prior to cleaning, further testing showed misfires on all cylinders.

Clarification on cleaning: Used CRC MAF cleaner.
The initial cleaning which did't fix things was a cautious, light spray from an inch away from the MAF. The cleaning which had an effect was placing the CRC red extension tube into the MAF inlet through the plastic screen of the housing. I used full pressure on inlet and then the outlet using a slight bend in the tube. I then aggressively cleaned the temp sensor on the side of MAF.
 
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Digging up an old one: when you said rough idle, was it something you could see reflected in the tach? My tach fluxes +/- 20-40 RPM at idle. Seems like most tachs in cars are smoothed, so they are fairly steady. Therefore I am unsure if my car idles rough or if the tachs in a Porsche are sensitive with a high resolution.
 

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Discussion Starter · #16 ·
I ignore the fine details in all gauges unless they are analog with no programmed processing (like my '69 911). Porsche and many other auto makers do not let the gauges reflect reality anymore. This also can change with the exact version of the firmware installed car.
Example: If you have access to the numeric car engine temp and look at your temp gauge. It will read in the middle for a wide range of actual temps. This gives the illusion of stability.
 
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