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This question already has an answer here:

I drive a used 2009 Toyota Matrix S (80k miles), and this is my first manual transmission car so forgive me if I'm describing something obvious and pedestrian here.

Recently, I've noticed some odd behavior when letting the clutch in to start from a stop: although everything is fine and smooth when I hold at 2000 RPMs, if the RPMs drop to 1300-1600, the clutch pedal will judder for a second as if I'm lugging the engine, until the clutch fully engages. However, I've never seen the engine lug over 1200 otherwise, even under heavy acceleration in 5th.

Worth noting is that this only happens when I'm accelerating and engaging the clutch relatively hard - one of those "oh shit, the light turned" situations we've all had. I don't experience this during light acceleration at all, and my solution when I need a little power from a stop has been to just peg the engine somewhere between 2000-3000 RPMs and slip the clutch a lot.

Now I'm no mechanic, but my instinct is that this is somehow to do with the added strain on the clutch. I'm not dropping it, but I wonder if the heavy load is accentuating some sort of mechanical warp or weakness, courtesy of either the previous owner or a long service life. I'm guessing the solution either way is "be nicer to your clutch."

But, I'm still curious: Why might my clutch be pulsing under heavy loads?

marked as duplicate by tlhIngan, Bob Cross Jul 28 '18 at 12:08

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • Welcome to Motor Vehicle Maintenance & Repair! How many miles are on the clutch (is it the original clutch)? Do you ever do any "spirited" takeoffs in the car? If so, what's the frequency of it? – Pᴀᴜʟsᴛᴇʀ2 Jul 27 '18 at 15:11
  • I'm pretty sure this is the original, so that would be 80k miles on the clutch now. And I'd certainly be lying if I said I hadn't done a couple of "spirited" takeoffs with my new used car, but those were a few months back, and numbered on one hand. I can't, however, speak to the driving habits of the owner before the 75k mark. – Chris Brace Jul 27 '18 at 15:18
  • Browsing more, I think I may have found a potential answer to my own question: link – Chris Brace Jul 27 '18 at 15:24
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I don't really know the etiquette on this, but I think I'm going to answer my own question here: based on another question from this very exchange, it seems that this judder/bounce/pulse is a known feature of many drivetrains at low RPMs and medium-high torques, occurring due to mediocre clutch finesse and the lack of oscillation dampening in the drivetrain serving to create stable oscillations at low RPMs, no clutch damage required. As Caius Jard said there,

hitting the right frequency at the start and maintaining a little bit of motion input will keep things bouncing

My specific case actually matches almost perfectly to OPs there, as this became most noticeable this week after a couple of particularly wet, rainy days. I'm not sure whether this actually influences the clutch as much as OP claims, but it certainly fits the profile.

Anyhow, since this question is essentially a duplicate, I'm going to accept my own answer and move on. Please let me know if there's anything else I should do with this question - like I said, I'm new here!

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