Piston Slap: The Kid's Got a Point, Dear

Sajeev Mehta
by Sajeev Mehta
piston slap the kid s got a point dear

TTAC Commentator Silent Ricochet writes:

Hi Sajeev, I am the owner of a 2002 Chevrolet Cavalier Z24 (has the 2.4L LDR motor in it) with about 128,000 Miles on it. I being a teenager, have my fun with it, but also baby it when it’s cold out, let it warm up plenty, even in the summer, and give it an oil change every 3000 Miles; no excuses. The car has a 5-speed Manual Gearbox, and I’m trying to figure out this awful noise that comes from my car when shifting from time to time. In any gear, other than first, if the RPM’s are too low for that gear (usually under 2000 RPM), the engine is kinda sluggish (that’s expected). What isn’t expected is this weird metallic vibrating sound that comes out of my car. Happens often when being in too high of a gear when going around a turn (even in 2nd gear, and I can’t put the car in 1st around a turn unless I’m doing under like 5 MPH). Pressing the gas harder to raise my RPM’s quicker does nothing, if anything just amplifies the sound, so What I must do is either downshift to a lower gear if possible, or just lightly hold my foot on the gas until I get back into my Torque band around 2400RPM. The noise can be hear well outside of the car, as I get looks from people walking by when the noise is made, and I can even hear it reverberate off the houses in my neighborhood when my windows are down. What is this noise and is it a cause for concern?

Sajeev Answers:

Being a teenager with a hot-ish stick shift car, you like to “hoon” around, right? If so, today’s is your lucky day, because you’re getting the hot-rodder’s equivalent of money in the bank: a busted component that is cheaply replaced with a go-fast part.

Pretend you live in a stereotypical 1950s TV family sitcom; your (nuclear) family is sitting down at a sea foam green dinette set for dinner. Mashed Potatoes, beef and nothing made with high fructose corn syrup. You tell Mom and Dad about the “ruckus” you make in the neighborhood, and the fun and cheap fix for it. When mentioning the fix/performance upgrade, Mom frowns. Your little brother giggles. And Dad, with a slightly evil grin says, “the kid’s got a point, Dear.”

If the Z24 makes that much of a racket around the neighborhood at low rpms, there’s only one explanation. That’s right, my guess is an exhaust issue. Loading the motor like this is known to exacerbate a loose or rusty rattle in the exhaust system. And if you live in the rust belt, you can “bet your sweet bippy” that one or more exhaust part is rusted to the point of rattle.

So here’s the advice: find a (non-franchise preferred) exhaust shop in town and ask them to look under your ride. I suspect the rattle is a heat shield on the catalytic convertor, but it could be any welded point on the system. Bad mufflers or resonators are entirely possible. And remember, if you can replace it with an OEM-equivalent part, you can do better in the aftermarket for about the same. But please, no ricer fart pipes, keep the upgrades sane.

Send your queries to mehta@ttac.com. Spare no details and ask for a speedy resolution if you’re in a hurry.

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2 of 37 comments
  • JimC JimC on Nov 15, 2010

    I think everybody pretty much whipped the noise issue. For the 2-1 downshift, yeah, don't bother shifting into 1st unless you're almost stopped. Even as late as the 1950s and 1960s there were still manual transmissions built with non-synchro first gear. Food for thought. But... Why is your 2-1 so difficult? At 128,000 miles it is worth your while to change your transaxle oil- just make sure you do it right (get the right oil, remove the filler plug before you remove the drain... just in case the filler won't budge, be careful not to underfill on the refill). That and some parts of the clutch might be wearing out- is there a freeplay adjustment on these cars? (Not all manual transmission cars have that though.)

  • MRL325i MRL325i on Nov 15, 2010

    Slightly OT, I looked at one of these today as a first car for my son. It was a 2000 Z24 with an autobox. The guy kept it in very good shape, and it had less than 60k on it. But, man, what a POS. The I could feel the frame under the seat cushion, the doors needed a good slam to latch -- just everything about it seemed bean counted to death. Maybe it is a decent car, but I couldn't get past the overall crappiness of the thing.

  • Chuck Norton And guys are having wide spread issues with the 10 speed transmission with the HP numbers out of the factory......
  • Zerofoo "Hyundais just got better and better during the 1990s, though, and memories of those shoddy Excels faded."Never. A friend had an early 90s Hyundai Excel as his college beater. One day he decided that the last tank of gas he bought was worth more than the car. He drove it to empty and then he and his fraternity brothers pushed it into the woods and left it there.
  • Kwik_Shift There are no new Renegades for sale within my geographic circle of up to 85 kms. Looks like the artificial shortage game. They bring one in, 10 buyers line up for it, $10,000 over MSRP. Yeah. Like with a lot of new cars.
  • Ribbedroof In Oklahoma, no less!
  • Ribbedroof Have one in the shop for minor front collision repairs right now,I've seen more of these in the comments than in the 30 years I've been in collision repair.