Diagnosing Clutch Shudder / Hesitation When Pulling Away
 

Hey all,

Hoping someone has some good pointers for an issue I've been having on my '00 S with ~41k miles. The last three weeks or so I've been having what seems like a minor hesitation/sputter/bucking when pulling away in first gear. Almost like a misfire stutter, except no codes are pending or stored. I'm led to believe this is actually more of a minor clutch shudder as I've had a few more severe cases when letting the clutch out a bit faster where the car bucks and shudders more as I'm pulling away.

Some notes:

• This started happening as the weather got cold, although FWIW I think this is coincidental.
• This seems to go away, or at the very least is heavily minimized, once the car has warmed up. Recently I've been only doing short drives to and from work, ~5 miles each way, so it's been noticeable. A longer drive today and other than leaving my house I didn't have much of an issue.
• The clutch operates smoothly otherwise, no issues upshifting or downshifting into any gear.
• The clutch isn't slipping in 5th or 6th with my foot to the floor (or in any other situation)
• 9 months ago I dropped the trans to reseal the IMS (improperly installed seal from previous owner) and replace the RMS. I have little reason to believe oil is getting on the clutch and then burning off as both have fresh seals less than 2,000 miles ago and the bottom of the bell housing where the IMS/RMS leak manifests is bone dry. I left the flywheel, clutch, and pressure plate alone - the clutch was pretty new (3 years and <10k miles or so?) but I do not know about the flywheel. It may be the original.
• I do occasionally get some squeal when operating the clutch a lot (e.g. three point turn). Sounds like a belt squealing. I assumed this was the throwout bearing which I replaced when doing the IMS/RMS seals. Perhaps foolishly I did not replace the bearing's guide tube. If relevant, my car does have the upgraded 987 clutch fork.
• Brakes and fluid were bled 1.5 years ago when doing pads and rotors, but I did not bleed the clutch specifically when doing this.

What should my next steps be? Reading up on similar forum posts tells me this might be a failing dual-mass flywheel, but I'm not sure why that would improve as the car warms up. I have no problem dropping the transmission again over the winter but I'd love to not if I don't need to. If there's something I can do to diagnose the issue further before just throwing money at it (those DMFs aren't cheap!) I'm all ears.

Have you tried to isolate the issue to engine vs clutch? If you let the clutch out while the engine is idling, and then accelerate, does it happen on clutch engagement or is it on acceleration?

Fairly certain it's clutch. It's definitely happening on clutch engagement although revs do play into it. I had a bad MAF sensor this spring that caused some lag on hard acceleration but I replaced that with an OEM MAF. This feels more mechanical than that did - especially if giving it some revs for a harder start, I get more of a 'bucking' until the clutch seems to grab and then everything is perfect until I have to go from a stop again.

My 98" Boxster has done the same for years (96,000 miles).

I notice that the clutch engagement is much more "touchy" the very first or second time I start driving after its been sitting overnight or a few days. IF I "baby" and very easily engage the clutch and throttle the first time or two....no shudder and everything is fine afterwards.

I'm always a smooth and easy clutch operator and never press the car or track it. Could it be the clutch sending me a message?, maybe, but for now I'm not going there.

This may have nothing to do with your problem, but have you checked the engine and clutch mounts? I had some of you symptoms on my 924S when the tranny mounts gave up the ghost.

I'll have to check on these next time I'm under the car - the trans mounts seemed OK when I removed them doing the last service but I didn't explicitly check them. I suppose there's always the chance I goofed on something when putting them back...

A bit embarrassed to be making this post, but I think I've solved the issue...

Other than an oil change I didn't have much maintenance to do over the winter so I didn't tear into the car. Driving it some more this spring I started leaning more towards a MAF (or other air) issue. The transmission feels great through the rest of the gears, and if I let the clutch out slowly I had no issues but the engine seemed bogged down for a second or two before 'catching up' to the gas pedal. This doesn't really lend itself to a transmission issue, so this week I finally found some time to dig into the engine bay and take a look.

My plan was:

1. Remove and clean the MAF. I replaced this with a Bosch unit last spring, so I was hopeful this wasn't an issue.
2. Remove the throttle body and clean it
3. Perform the throttle position calibration / relearn

When I went to remove the throttle body hose clamps they were... already loose. I forgot to tighten two of them last time I was in there. Talk about a silly mistake. I still cleaned the MAF and throttle body as well as performed the throttle position calibration, but I'd put money on this being the issue. The car was either getting or losing air in between the MAF and the intake, and the 'clutch shudder' I was feeling was just a jerky start due to the engine not knowing what to do on more aggressive starts.

At least it was a cheap fix :)