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Severe Engine Shaking 2500-3000rpm on hard acceleration

 
Old 08-26-2014, 12:07 AM
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GregL
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Default Severe Engine Shaking 2500-3000rpm on hard acceleration

I could really use this forum's expertise!

I recently purchased a 997.1 Turbo. I've noticed that the engine has a heavy shake when accelerating hard (with boost) between 2500 and 3000rpm in any gear. When no boost is registered there is no shake. The shake is very obvious in the steering wheel and most obvious in 6th gear mainly because you accelerate through that rpm range the slowest in 6th. However you can feel it in every gear. The shaking is pretty severe.

I had the tune checked by a local shop and they said the tune is good. A guy at the shop also test drove the vehicle and noticed the shaking as well.

The spark plugs have been replaced and regular maintenance has been completed recently and that hasn't helped this issue. The engine computer isn't throwing any codes.

Does anyone have any ideas of where to start looking for the cause of the issue?

Thanks!
Greg
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Old 08-26-2014, 04:27 AM
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Clutch issue > maybe a dual mass flywheel failure...
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Old 08-26-2014, 08:50 AM
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Interesting. I just had a sachs 2.5 installed but kept the stock flywheel as I was told it's in fine condition. However since the clutch install I've had a very severe gas pedal vibration, it seems to get worst as it gets closer to 3.5rpm's. And when I give the car hard acceleration, the entire center console shakes. Not trying to hijack the thread but figured we could be having a similar issue, maybe my clutch isn't seated correctly?
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Old 08-26-2014, 09:46 AM
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My initial thoughts would be clutch, or engine mounts, based on the limited information. I would not waste time checing things like the tune, etc.. That is likely NOT going to cause shaking.

Another possibiliy is tire balance and/or worn suspension parts, but sounds like you ONLY get it during hard acceleration which leads me to think Clutch or Engine mounts (or possibly tranny mount).

Good luck,
DC
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Old 08-26-2014, 02:47 PM
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With the amount of low RPM torque that this engine makes, replacing a clutch without replacing the dual mass flywheel (over 50K) miles is a risk... The risk is the monies you have to spend to go back in to install a new one.
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Old 08-26-2014, 04:02 PM
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GregL
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Default Power Delivery Shudder

Thanks everyone for your responses so far. I have more information that may change your thoughts.

I took the car out for another drive and I would now describe the problem as shuddering of the power delivery from the engine. It is definitely not a mechanical shake from the wheels, it appears to be coming from power delivery from the engine. It is a HIGH-TORQUE->LOWER-TORQUE->HIGH-TORQUE->LOWER-TORQUE fast cycle that gives the car a good shake.

Once the car reaches about 3kish rpm or so the delivery is smooth all the way to redline. The problem only seems to occur with high boost. 0.5bar boost still gives smooth power delivery through the 2500-3000 range. So it is basically a problem when I WOT.

The car has 54km (34k mi) on it. It has a tubi style exhaust and BMC airfilter but otherwise stock. The turbos do woosh a bit when accelerating in the lower rpms (2500-4000) which may be a problem? Also my cold start warm up RPM is 1.9k for 30sec before dropping to about 900rpm. Not sure if this is related at all.

Today my car threw a CEL: P1372 Valve lift control, above limit value
Note:
- For this diagnostic, the cylinder preceding in the firing order can also be affected.
- If misfires are entered simultaneously (P0300 to P0308), these must be worked through first.
- If only valve lift errors are entered, please also check the cylinders preceding in the firing order.
Example: If the valve lift error for cylinder 4 (bank 2) is entered, the mechanism of the valve lift switching of cylinder 2 (bank 1) is also to be checked.
- Valve lift error detected via evaluation of rough running, similar to detecting misfiring.
- Parity check errors during valve lift control only entered together with cylinder-specific faults.

Possible fault causes
- Valve(s) of a cylinder stay jammed in large stroke
- Valves of different cylinders stay jammed in large stroke (parity check error)

This was triggered when I was driving 90km/hr at 2.7krpm with 50% throttle. There were no misfires recorded. Not sure if this is related to my problem.

Does the engine computer change how it operates the engine at WOT starting at 3000rpm? I'm confused about how power delivery could be smooth 3k+ rpm WOT but 2500-3000rpm it shudders.
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Old 08-26-2014, 04:47 PM
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How often do you change your engine oil?

Plugs were changed when?

The valve lift solenoid might be failing OR this is the beginning of the dreaded camshaft sleeve failure.

You have two major intake valve cycles taking place. The low lift/high lift inlet tappets are closing and your vario cam module is advancing the intake camshaft. The shutter is due to engine timing being controlled, one side of the engine bank is working one is not.

You should take the car into the shop to check the solenoid, and connections. BTW, when have you washed your BMC filter.. With this engine I wouldn't be running one. The stock filter is large enough to handle the CFM's on stock turbochargers.
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Old 08-26-2014, 05:09 PM
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Hey Kevin. Thanks for your thoughts!

I bought the car 4 weeks ago and it came with the current modifications. Unfortunately I have no information on previous service records. Last week the car went in for maintenance. The engine oil, oil filter was changed and new spark plugs installed. The mechanic said the engine sounded like it was running well. I don't believe the BMC filter was washed on this maintenance and I have no idea when it was last washed. Do you recommend I install a new stock filter or just wash the existing one?

I've got a service appointment booked for a week friday (first available spot -- argh). This is my DD, do you see there being a large risk if I continue driving this vehicle moderately to and from work?
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Old 08-26-2014, 05:38 PM
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I'd replace the BMC with the stock filter.

This is an important issue. I'd take the car into your Porsche dealer. Have them provide you with a loaner car/rental car.
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Old 08-26-2014, 07:12 PM
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Thanks Kevin, much appreciated!!
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Old 08-27-2014, 12:31 AM
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Greg. Interesting, please keep this post updated. Reading this makes my mind wonder... I have noticed intermittent clutch since I tuned my car which I expected eventually. It subsided and now does something similar, almost seems like a clutch slip yet doesn't. I notice primarily in 2nd under roll on with decent boost. Car is a little "lurchy" like a "slip->grab- slip" condition. Turbos woosh like you stated. I don't have the heart to stay in it so I usually feather off throttle and it stops yet under still decent acceleration. If I keep out of boost all seems pretty well. However no shake of my center console occurs at any point...I self diagnosed that it's clutch related and recently slipping, I figure it's time anyways, I anticipate it to fix my issue, but now I wonder if it could be something else?

Like the 2nd poster, it's being recommended that I should be able to do the sachs 2.5 (ordered and install appt Thursday) and considering the 30k miles the stock dmfw "should" be fine.... I kind of 2nd guess it all right now as a result if this post and the comments. I am getting plugs done at the same time just for good measure and that they have not yet been changed and I think is recommended at 30k. Hmmmm thanks
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Old 08-27-2014, 02:25 AM
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One must be careful with your clutch components and install. There is NO factory Sachs Stage XYZ or Stage 1, 2 and 3.. What one shop or person calls a Stage 2 might not be what another person calls it. Regardless, If you have a slipping clutch and you install a new disk and new pressure plate on the OLD dual mass flywheel, you risk engagement shake and shutter. Flywheels that are older than 50K miles are going to fail. Please realize that the flywheel has a rubber center. The rubber gets hard and fails over time, the friction surface heats and checks, very similar to a worn brake rotor. The dual mass flywheels are inexpensive when compared to going back in and spending labor dollars to get it fixed.

Second note, the factory clutch disk, has a sprung center. This absorbs the shock when you shift. It decouples the transmission/engine. The dual mass flywheel is the second line to prevent harmonics. With many of the kits sold, many are sold with a solid non sprung disk. If you do not install a new dual mass flywheel, and have less than a stellar surface, engagement shake and shutter will occur. Many times the new clutch disk will require miles of service to wear in, similar to just installing pads on old rotors. In extreme cases, the disk will slip. For car that are not tracked, I recommend the sprung disk, not the solid disk. The sprung disk will absorb a lot of the shock from when you shift, and have those rough starts in first gear. Additionally the sprung disk with shield the dual mass from excessive wear. Please realize that the dual mass has wear limits for rotational movement >>greater than 10mm left and right, total of 20mm movement requires replacement.

Third note, Stage kits have different pressure plates sold and packaged. For the 997TT, I recommend nothing less than the Sachs Race Engineering plate ending in 764.. Not the 752 plate. In extreme racing conditions modified plates can be used.

Pick you components wisely, you are the one driving your car.. The Sachs pressure 764 pressure plate, stock 997TT clutch disk and new dual mass flywheel will restore your clutch to better than stock and will hold 90% of the tunes with stock or GT2 turbochargers (a drag car is a different story).
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Old 09-13-2014, 03:31 PM
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GregL
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Hey Guys,

I'm happy to report that the dealership I bought my car from kindly diagnosed and fixed the issue for me. They reported that a VGT actuator link came off so one of the turbo vane's weren't being adjusting. They said its possible with the wheel off to check if the turbo actuator link has fallen out of place. This fix has resulted in a dramatic increase in power and fun. Thanks so much for your advice on this issue. Hopefully someone else finds this useful in the future.

Cheers
Greg
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Old 09-13-2014, 07:02 PM
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I'm surprised that didn't throw a CEL code?
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Old 09-13-2014, 07:47 PM
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GregL
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I wish there was a proper engine code. It would have saved a lot of stress.

For the first 20 days of driving (almost every day) no codes thrown despite obvious power delivery issues. Eventually under a certain condition when I was driving aggressively it threw code "P1372 valve lift" which I believe gets triggered from an engine vibration sensor. At least having "a" engine code will get the porsche mechanics something to go off versus I'm sure we've all experienced the mechanic saying: "Yes sir, I agree what you're experiencing is abnormal but the engine isn't throwing any codes/misfires and says everything is running as intended so we can't look into this any further".
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