[Sculler]

Okay sorry, didn't have a clue what to title this.



I've owned my 968 (92 manual coupe, 55,000 miles) since last November. I had the shop that did the <acronym title='pre purchase inspection'>PPI</acronym> do belts, & cam pads & chain. The shop in Omaha is recognized Porsche shop. Also, the car was used in DE events by <acronym title='previous owner'>PO</acronym>. It is completely stock.



When driving the car it's very difficult to be smooth as there is such a dramatic transition between on throttle and off throttle. Trying to travel at a relatively steady speed (say 35 mph) in second or third is near impossible. If you lift off throttle or add throttle just slightly the car bucks. It seems like there is either a whole lot of drag when lifting off throttle or a huge amount of slop in the drive train like really worn U joints. <acronym title='previous owner'>PO</acronym> claims no issues like this prior to sale.



Just looking for any comments? Unfortunately I've never driven another 968 so no idea if this is normal or what might be causing the problem. I have yet to find the joy in driving 968!

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[flash]

you definitely sound like you have a significant problem.



is this car a manual or tip?



do you hear any clunking on and off throttle?



have you looked at the throttle cable and verified that there is not an undue amount of slack at idle?

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[Sculler]

Flash.



Manual transmission. No clunking. Haven't had throttle cable checked so will do that. Does this sound to you like it could be a timing problem? I'm wondering if maybe the timing was not set properly when the vario cam pads and chain were replaced. I really do think that something took place when I had the work done in Omaha. The <acronym title='previous owner'>PO</acronym> was a really great guy and I do not think that he would have miss represented the car.

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[flash]

while anything is possible, what you describe does not sound to me like a timing problem.



however, check the hall sender, clean the MAF with MAF cleaner, and check all vacuum hoses. those things can make for some pretty uneven running.



loose spark plugs can too. it's very important that one actually uses a torque wrench on those.

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[94SilverCab]

My first thought was "throttle cable". Before you get all wrapped around the axle, start with the easy/cheap stuff.



JMO,



Jay

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[Sculler]

Thank you. I've pulled the car from the local dealer and tomorrow have it headed to an indie recommended here. Will share your thoughts with the indie and post progress.

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[Ryan]

Does the car have a non-stock flywheel?

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[Sculler]

Delivered car to Euro Autowerks in Rockford MI yesterday. Tim Thatcher, the owner took a ride with me and his immediate reaction was that my DM Flywheel needs to be replaced. He said there are no universal joints so driveline slop that I have between on and off throttle is most likely coming from worn DM flywheel. Tim also noticed a fair amount of vibration with hand on shift lever.


I've read most of the threads here about flywheel issues and have not found one where the complaint is about driveline slop (feels like worn universal in older rear drive car).


Just wondering if any experience here can confirm Tim's diagnosis before going ahead with $3,000 + repair? Price related to doing everything else while in there.


Car has 55,000 miles and was used for DE. Clutch, flywheel are original and clutch operates smoothly.

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[Sculler]

Re posting. Hoping to get some comments. Slop caused by worn DM Flywheel?

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[Waylander]

My coupe has done 141K just replaced the clutch, the DMF was still fine, I have seen this bucking around when the cam timing was out

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[Grandpa#3]

I find it rather hard to believe the flywheel needs to be replaced with only 55k miles. The shift vibration can be caused by a worn shift lever along with the shift linkage on top of the Transaxle. I take it you do not do any wrenching on your car but rely on shops to fix any problems on your car. The link below shows and tells how to take out the slop/vibration in the Shift Lever.

http://www.clarks-garage.com/shop-manual/trans-07.htm

Cheers,
Larry

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[bombfactory]

The 968 shift lever is notoriously 'buzzy' and the transaxle can get a bit 'clunky' (sometimes I get a light clunk sound from the rear when I put it in first from neutral). Someone not familiar with our cars (about 95% of Porsche mechanics unfortunately - no matter if they tell you otherwise ;-) could attribute these things to the DMF 'going bad', but those things are pretty robust. I'm at 130k miles, had the clutch done recently and the DMF was fine. YMMV - I hope the problem is something less expensive!

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[Ryan]

I would want to know why the problem was not caught in the PPI.

 

The flywheel could be toast at that mileage due to downshifting without rev-matching and bad driving style I guess. At this age the elastic properties could be going south.

 

Hope this is not the case (for your wallet)

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[flash]

a dmf is extremely hard to diagnose.  it requires pulling the bell housing shell off, and conducting a rebound test.

 

a dmf will not generally exhibit the on/off symptom, but rather only an "on" backlash.  it will generally exhibit a vibration.

 

the backlash, if on and off throttle, could easily be the collar from one of the torque tube bearings having slipped out of the bearing.  this happens more than you might think.

 

a bad pilot bearing can also do this.

 

there could be an input shaft bearing buggered.

 

no matter what the problem is though, things are going to have to come apart to diagnose it.

 

i would definitely hold the shop responsible for the diagnosis.  if they fix one thing, thinking it is the problem, and it does not solve the problem, they should eat the labor.  parts should still be paid for by the customer, but not with a full markup, as those parts would not need to be changed at this time, were it not for the misdiagnosis.

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[Sculler]

Well thought I would give a follow up report. My 968 is finally sorted out and drives perfectly. Tim at Euro Autowerks in Rockford, MI is responsible for correct diagnosis and completing the work. The biggest issue was an absolutely trashed DMF and a frozen clutch shaft. So I have a new DMF, pressure plate, clutch, clutch shaft, slave cylinder, engine mounts, distributor, spark plugs, & fuel filter. Both my stalling problem and driveline slop are fixed! Hallelujah. Not sure what the DMF had to do with stalling but there must some impact.


Tim found a number of issues that should have been identified with the PPI. The most significant, the trashed DMF. He identified the issue within about a mile of initial test drive. He also retrived a dropped washer down next to a spark plug and corrected a spark plug seal way out of position. I am now a smiling 968 owner.

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[KRAG50]

Good for you, I always heard good things about Tim.

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