Check 996 vibration

Anyone with a 2004 996 would you please check the following on your car. When running and in neutral, foot off the clutch, gradually bring the RPMs up to a little over 2000. What I am interested in knowing is if you notice any change when the RPMs reach 2000. The change that occurs on my friends 996 is just for a second as it passes 2000 RPM and it feels like a second of slight vibration. Almost like something changes (i.e., timing, etc.) It does not affect the performance and is just in the 2000 to 2050ish range. It is driving us crazy trying to figure out if it is normal or an issues. Thanks�

I had vibration issues, including the clutch pedal, with my '99 C4 that were noticeable at the "harmonic balance" area of 55 mph in 4th. No one was able to figure it out. I have clutch pedal vibration issues with my '07 997S that are discussed elsewhere on this website, though not the vibration you describe. Try determining if there's a vibration at 2000 RPM when in gear. One wonders why Porsche has to have so many vibration issues other than to accept the usual factory blab that it comes with owning a race-bred machine.

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I have an 03, but they are the same. What you are feeling is the variocam doing its thing changing the valve timing. Search variocam and all will be clear. Perfectly normal, and it happens in gear too at about 2200 rpm.

I have on 04 C2 and just checked this out. Mine does have a vibration, similar to the feel of a rough idle, that you can feel andhear at exactly 2,000 rpm, it is steady. Smooth as silk at 1800 and 2200. Not sure this means it is normal, just that my car does do this. Don't think I would have ever noticed it if you hadn't mentioned it.

DCP ... you're spot on about the camshaft feature being the cause. I had forgotten about that.

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Actually, I think I am wrong. The varicam makes its change at 3,200 rpm, no?

Good subject. I have a 2004 996C2 6SP and have noticed the same vibration that pmkazz has described and it�s driving me crazy. I�ve done a bunch of diagnosing and still cannot pinpoint the cause. Here are some of the tests that I made; 1) swapped motors mounts from driver to passenger side 2) loosened and retightened exhaust system 3) Tested w/o mufflers 4) tried 100 octane fuel 5) replaced clutch and DMF 6) temporarily disconnected variocam timing and lift solenoid valves (i.e. basically disabling both features of variocam plus) 7) tried 0W-40 and 15W-50 weight oils 8) supported mufflers and cats with floor jacks I connected my Durametric software and checked all parameters. I did find something interesting when comparing �rough running cylinder 1-6�. I used Excel to calculate the standard deviation of the rough running values obtained from Durametric and noticed that when the vibration occurs, cylinder no.4 runs significantly rougher than the other cylinders. At the other rpms it is in line with the others. no 1 no 6 no 2 no 4 no 3 no 5 idle - 1300rpm 0.229 0.079 0.128 0.161 0.160 0.126 1300-1700rpm 0.336 0.231 0.557 0.302 0.396 0.163 1700-2050rpm 0.159 0.126 0.084 0.724 0.387 0.140 Tomorrow I plan to check spark plugs and swap ignition coils to see if the rough running shifts to another cylinder. The vibration is subtle at times but more noticeable when it is cool outside. I have observed the same vibration on other 2002 � 2004 model, 6sp and tiptronic, but to a lesser degree. I have not noticed this in 1999 � 2001 models. The later models have a different cam timing chain arrangement, intake cam advancement mechanism and intake valve lift. Perhaps the cause is due to these difference but there are still a few more things to check out. It would be great to get some feedback from other members.

I am not sure if this is useful information or not but here we go. When I initially purchased my 996 I noticed the same thing, as well as a passenger seat that was noticably vibration as well. The records that the previous owner had showed no indicaiton of the trans mounts and motor mounts being replaced throughut its 77k life so I did so. The vibration is gone for the most part but at times it seams to re-occur. I have not noticed a relaitonship between how often the car is driven, or different weather conditions or driving styles. I essentially have chalked this one up to the same gremlin that causes my sunroof to go wacky occasionaly.

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Al-x, What year is your 996? I investigated replacing the motor mounts but have been told by several technicians that the mounts seldom fail. I still consider them to be a possible casue. Had them replaced in my E430 and it made a difference.

After reading my response I noticed how terrible my spelling and grammar was, wow my apologies. Anyway it is a 99 tippy and the motor mounts were begining to show there age. The tranny mounts on the other hand were absolutely destroyed. Again this did cure the problem for the most part but it does come back occasionally. Hope this helps

DCP, your first answer was right -- about 2200 when the varicam kicks in.

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wbgordon, I disconnected the variocam plus solenoids, the one for advancing the cam timing and the other for controlling the intake valve lift and still observed the vibration at 2000 rpm. With these solenoids disconnected the hydraulic control is disabled so there is no way to advance the cam timing or change the lift.

George996, How bad is the vibration? Can you feel it through the clutch pedal? Is it only related to RPM and not to MPH?

I'm not sure I agree with the Variocam RPM activation range. It actually engages at 3300 RPM and Porsche states in the manual not to launch the care with less than 2000RPM. Please not that the Variocam activation is not progressive...it is either on or off. What you should feel when the Variocam engages is a bit a of flat spot on the torque curve and that's it. There is no vibration. I would suggest checking your flywheel mounts or your engine mounts. The Boxer engine is very, very stable in terms of vibration without the use of counter balancers. My problem with my 996 is feeling some vibration on the clutch pedal...there is no explanation for it! Go figure.

wbgordon, The clutch pedal is released and foot not on it. You can feel it just as you bring the RPM from idle and hit 2000. Then it almost feels like something changes in the engine timing or air/fuel exchange. And then it is only for a second 2000 to 2050. I would think it is the Variocam activation but george996 said he disconnected the solenoids and still notices it on his.

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wbgordon, the vibration is not that bad but now I am focused on it. There is a distinct difference when the engine is at 1950-2000 vs other speeds. No vibration coming through the clutch. As I mentioend, I disconnected the variocam timing and lift solenoid and the symptom is the same.

Don't know, George. Wish I could be more help. Keep pluggin', though, and eventually you'll find out why.

I am following up on post above about chasing down rough running. Just to recap, I connected my Durametric and found that cylinder 4 was running considerably rougher than the other cylinders at 1950-2000 rpm. It was in line with the other cylinders at lower rpms. I swapped the spark plug and coil for cylinder no.4 with no. 6 and the problem shifted to no. 6. The engine still behaved the same, vibration at 1950-2000 rpm, for about 15 minutes and then smoothed out significantly. Went for a test drive and it never ran smoother. Then I reconnected Duramtric expecting not find any roughness and surprisingly the data was the same, no. 6 was significantly rougher but the engine feels smooth as silk. I plan to replace no.6 coil and all plugs hoping the vibration is eliminated for good. Do you think that the DME adjusted for the change? Any comments?