968 Shudder on Acceleration

[Jamie '92 968]

My '92 968 (135K miles, original clutch) recently developed an occasional shudder during acceleration.
It usually happens at low RPMs (~2K to 3K) when I give it near full throttle.
The shudder is pretty strong and there is a definite loss of power.

It first happened about a month ago on the way home after spending a small fortune at the dealer for a new lower balance shaft cover seal (I believe this involves removal of the timing belt). Coincidence?? I should have turned around and taken it back, but I down shifted and the problem went away. It was OK for several days before it started to reappear every once in a while.

I'm thinking timing, fuel pump, clutch , differential, ???

I had a local shop (not Porsche specialists) take a look last week, but of course the problem did not show up for them.

Any ideas on the cause, or suggestions for diagnostic steps would be very much appreciated.

THANKS!

[flash968]

while it is possible that the belt is off a couple of teeth, it is very likely the DMF, or at least a glazed clutch

i would call rs barn - they aren't far from you, and pretty much all they do is 968s

in the meantime, are there any other new vibrations or smells?

[Jamie '92 968]

Thanks for the quick reply, Fash!
This is the first time I've posted a question on the forum, though I've spent hours searching, brousing, and soaking up great info. I haven't found anything right on target , so I really appreciate the direct response.

First... DMF? Sorry, I'm still adding to my inventory of TLA (Three Letter Acronyms).
Also, what's a glazed clutch?

I checked the web site for RS Barn. Amazing that there was a colony of 968 specialists only an hour's drive from me and I never knew it. Thanks for the tip.

As for other symptoms, the car is 17 years old now, so there is a pretty good list of things going on. Since you asked, here are some of the ones that may or may not be related.

- It's been difficult to shift into 1st gear lately, from a standing stop, when the transmission is cold (first 3 or 4 minutes of driving). After that, it feels fine. I changed the transaxle fluid last week, and that had no effect. Usually, I can find one gear that I can shift into, and after that (lining things up?), I can get into 1st.
Again, once it's warmed up, it shifts fine.

- There has been more "engine" (?) vibration lately (ever since I had the timing belt replaced last year... also a coincidence?). Feels like the balance shaft belt is off a couple clicks, but I had that checked when I had the oil leak fixed last month, and was told that it is OK. I mostly feel the vibration through the clutch pedal and shift lever. Sometimes it's bad enough to put my foot to sleep.

- The original reason I had the car in for service last month was that the oil pressure gauge stays pegged at zero when I start the car. Scary. After anywhere from 2 seconds to 2 minutes later, it will pop up to a normal reading. They replaced the oil pressure sending sensor, but it didn't change a thing. The mechanic at the dealer assured me that the engine was getting oil, and that it must be a bad gauge. Note that the warning light at the bottom of the pressure gauge does not come on, even when the gauge is sitting on zero. This might support the theory of a bad gauge.

- There is some noise evident when I hold the clutch pedal in, that goes away when I let it back out. I assume the throw-out bearing is probably on it's way out.

- I've been paranoid about the fuel pump now for a couple of years. It's making noise, but has been for 2 or 3 years now, and I had the pressure checked about a year ago and it was good at the time.

Like I said, lots of little things. I've been driving the car nearly every day since 1995 (and an 85.5 944 before that since 1987), so I'm pretty in tune with it's feel and sounds. Unfortunately, the cost of taking it to a dealer for service is killing me lately, so I'm actually afraid to have them look at it (stupid, I know). This forum seems to be a great resource to get educated and find a way to keep driving my dream car without going bankrupt or getting divorced.
Since the RS Barn is still a bit of a haul for me, any suggestions for a good mechanic closer to Delaware County in PA would be appreciated.

Thanks again for your help!

[flash968]

i'm sure pete would have a good suggestion of someone closer, but he's in newtown, so less than an hour away - he is THE guy, but as i said, he knows everybody, and if that is too far, he would know where else to go

DMF is Dual Mass Flywheel

you have a PM

[Jamie '92 968]

OK... I tried ... PM?

[flash968]

lol - no worries - private message - look up at the top right of the header of this page

[onZedge]

Originally Posted by Jamie '92 968

... DMF? Sorry, I'm still adding to my inventory of TLA (Three Letter Acronyms)...

You need to invest in a UAD.

[onZedge]

Universal Acronym Decoder

[JivenJim]

I second anything Flash or RS barn would tell you. Both of them are true friends to the 968 community. Thanks Guys.
I'm thinking possible Duel mass flywheel??
RS Barn sells a sweet aftermarket version
They'll know.

[Jamie '92 968]

Thanks guys.

If it is the DMF, are there any other symptoms I should be looking for to confirm the suspicion?

More importantly, since the problem is intermittent, is there any danger of continuing to drive the car until it gets worse, or do I risk adding to the expense of the eventual repair (or getting stranded someday)? How long do I Have?

[flash968]

if it is intermittent, i tend to think clutch disk - they will judder more when hot when they are about to fail - i would think you would smell it though if there was a loss of power

as for the DMF failure, the vibrations tend to get worse

the good news is that it is only a 4 hour job either way, unlike the 944

[rickharrison]

motor mounts? they can cause a shudder on acceleration too.

+1 on glazed up clutch disc too.

[flash968]

motor mounts usually show a vibration at idle, and the issues tend to be consistent - pretty easy to check though if you can get the car in the air

[Jamie '92 968]

I don't think it's motor mounts. I had them go on my old 944, and this doesn't feel anything like that.

The shudder in this case feels more like something grabbing and letting go at about 4 or 5 Hz. Sometimes it feels like a single bump. It's either happening, or it's not there. On/Off, not gradual.
Would a DMF feel that way?

Oh... and no smell either.

[flash968]

it could - definitely sounds like something amiss

does it do this in all gears? (trying to rule out anything in the rear)

[Jamie '92 968]

It's only happened a handfull of times total over the last month (when it started). Maybe 6 or 7 times.
I'm sure it's happened in 5th, and possibly in 3rd or 4th.

[flash968]

sure wish the car was here so i could check it out - i'd pop it over to pete at rs barn and see what he thinks - nobody knows these things better

[Jamie '92 968]

Thanks again Flash.
I've been trading e-mail with Pete today, and am planning to take a run up to his place to have him check it out.
Might be a week or so before I can make it happen, though.

Do you think it might be the LSD?

Any ideas on diagnostic experiments in the mean time would be appreciated.

[flash968]

not unless you have a clutch type (which is possible in a 92) - check the option code sticker in the trunk and tell me if it has 221

[Jamie '92 968]

There isa 220 and a 231, but no 221