jh1165

Hi everyone- just started having a new issue with my 2003 C4 S and thought I'd look to the collective wisdom here for a short list of places to start with for diagnosis. I noticed 2 days ago that the car shudders when going from stop to moving in first gear (manual transmission)- almost like its trying to stall. No problems once I'm moving a few MPH, no problems in any other gears, although I noticed this symptom in reverse yesterday as well. It almost feels like the clutch is slipping, if that makes sense; but once I'm moving I don't see the revs jump up or anything that would going along with a slipping clutch (from what I've read on that issue in general, anyway), and again no problems in any other gear. Car has 91K miles, not sure if its the original clutch or not. No change in clutch pedal feel.

I checked the brake/clutch fluid reservoir and the fluid is at the max fill line- was hoping it would be something simple like that that I could start with.

Sorry if this has been covered here before, but a rather extensive search has not yielded a thread that seems to be helpful for this.

So I'm thinking:
-clutch or related component, throw out bearing, etc?
-engine mounts?
-other bad things that I hope I don't have to think about right away

Any thoughts as for how to start diagnosing this would be GREATLY appreciated.

jh1165

Also, I recent ly changed out pads and rotors on the front (2 weeks ago). That's the only work that's been done recently aside from replacing the lower control arms on all corners about 6 weeks ago. I wouldn't think the brakes would have anything to do with this as I didn't disconnect the brake lines from the calipers, but I'm wondering now since the brake and clutch fluid are one in the same, right?

ditto

To test your clutch get on a highway at 50 mph and 5th gear and floor it. If the tach revs up initially and at a faster rate than the speedo, the clutch is on its way out. You will feel it too.

jh1165

Thanks, Ditto. Just did that several times. The revs and MPH climb steadily when I floor it from 50 in 5th gear. I also noticed that once the car warmed up I didn't feel the shuddering nearly as bad (maybe at all? I'm pretty sensitive to it at this point) in stop and go traffic on the way home.

So, maybe/hopefully not the clutch?

I read somewhere that a leaking RMS could drop oil on the flywheel and cause this, but I'd think this sensation would be evident in other gears as well.

My wrenching skills are not super strong, but I'm learning, and hoping I can try to find the culprit so I can figure out if this is just a small problem or a harbinger of something worse.

So engine mounts. Is there a way to look at these and see if they are bad/going bad?

DBJoe996

On the engine mounts, you can visually check by comparing the "droop" between the fender and left/right side exhaust pipes. If one side is lower than the other than that could mean a worn out motor mount. They can both be worn out and drooping. Difficult to say in that case. The stock motor mounts are filled with hydraulic fluid, so if it blows out entirely it usually creates a nasty leak under the car. Worn engine mounts contribute to shudder, passenger seat vibrations, and a loosey goosey feeling while shifting, cornering.

Brakes...probably not a cause. Lower control arms...hmmmm. There is a specific way they have to be installed. The inner frame bolt has to be tightened while the suspension is under load, and there is an index mark that has to be lined up. Who did your lower control arms?

I can't find the one for the rear, but here is the front:

jb1007

It may tend to shutter if you don't have enough rpms up while engaging the clutch when cold. If you don't notice it as much when warm might be just cold and give it a few more rpms.

jh1165

Thanks for the advice, guys.

DB- I just loooked at the tail pipes and they measure pretty even with respect to their distances to the bottom of the bumper. See photo below. I haven't noticed anything dripping in the regions of the engine mounts inside the engine bay or on the ground beneath the car. I can see the driver's side mount and it isn't covered in hydraulic fluid; can only see the passenger side from below but looks ok from that angle.

Greff in New Orleans, LA did my control arms. They are highly regarded in this area for Porsche service; but that was my first experience with them and I don't have any sort of comparison. But the shuddering really seems to be coming from the drivetrain somewhere as opposed to the suspension; but what do I know? If you were riding with me when it happens, I suspect it would feel and appear to you that I was a novice driver and about to stall.

The only other thing I can think to mention is that it's been raining here for the first time in over a month. I haven't driven through any deep puddles and I can't imagine a little moisture from rain on the road could cause anything along these lines.

PCAR996C2

Measuring the tail pipe "droop" in may experience isn't very helpful. I have had both of my mounts replaced and one side is still lower than the other, probably due to a misaligned tail pipe. You need to examine the actual mounts by getting underneath and checking for actual leakage.

DBJoe996

Probably a better thing to do is measure from the ground to the engine mounting plate, the big plate that runs across the engine and where the motor mounts attach.

There are three connection points for the entire motor/transmission. The two rear motor mounts and the transmission mount. The transmission mount can wear and get sloppy. If the transmission mount is not all torn up, there are silicone inserts that will beef it up.

Macster

Based on what you have posted (above and in other posts) it doesn't read like a clutch problem per se.

'course, you might want to get an experienced Porsche tech to check out the car.

As for a leaking RMS my info is a leaking RMS has never fouled a clutch. But there is always a first time. However, to know if this has occurred you would probably need to drop the transmission. That's a pretty expensive operation to do unless it is really necessary.

In the meantime, my recommendation is to do a brake/clutch fluid flush/bleed. You must be sure this fluid is not too old. "Too old" is 2+ years of service regardless of miles. I believe you are in the Louisiana area? If so with all that humidity... (Spent a summer in Lafayette LA and I still remember...)

Also, try a bottle of Techron. Add a bottle -- get the size -- the only size available? -- that treats 20 gallons of gasoline -- to the gas tank then fill up the gas tank with fuel. If you notice an improvement from the engine get a 2nd bottle and add that to the tank when the 1st fuel tank is down to 1/4 or so. Fill up the tank again.

It is recommended to then change the oil/filter as Techron can increase the level of contamination in the engine oil.

Might add that a few times I've left my 996 Turbo out in the rain it has run a bit rough upon cold start. I know some water got where it "shouldn't" because the in dash battery voltage gage read way low until the serpentine belt/pulleys dried out enough to spin the alternator. Oh, washing the car would have the belt slipping but the engine never ran rough.

My point is your car, your car's engine, could just be feeling the effects of being rained upon, unless of course you tell me the car doesn't get exposed to any rain.

extanker

dude...........have a mechanic road test your car...........................sans rain,oil leaks, gas and earth quakes

jh1165

Ok, great info here- thank you all so much.

Macster- the clutch/brake fluid is undoubtedly more than 2 years old. The previous owner had the last several years of service records (I've had the car for 4 months) and it looks like he did the basic recommended services, but no records of flushing this fluid. I'll start off with flushing the fluid.

The car was definitely exposed to rain- coincidentally the days it started this shuddering. and it's been extremely dry here the last two months, so maybe that's why it hadn't occurred before. I drove the car this afternoon and everything seems fine now- of course I'm hyper vigilant at this point, but I think everything is back to normal.

Thanks again for all of the great input.

docmirror

Not what you want to hear, but shudder on clutch engagement in lowgear or reverse is almost always a sign of faults in the clutch/PP/flywheel. It could be a slippery spot on the clutch friction disk, one(or more) of the tempered springs on the PP may be going out, bad flywheel surface condition, etc.

The shudder is the take up/slip out of the friction disk against the PP and flywheel. It's gotta come out and be examined. Sorry,,,,

relinuca

I agree with DOCMIRROR's posting, and I especially suspect a worn dual mass flywheel. The DMF seldom gets discussed on rennlist, but after replacing mine at 83K miles, the improvement in power train smoothness and clutch "pick up" was astonishing. (Unfortunately, one can only be certain as to the original poster's causes by pulling the trans and close inspection of the major components by an experienced eye.)

relinuca

dporto

^This^ and uh...Wash that thing ! Maybe it's just pissed at you!!!