Piston Slap: Playing Super Breakout by Itself?

by Sajeev Mehta

Updated: May 16th, 2014 Published: January 23rd, 2012

piston slap playing super breakout by itself

C.V. writes:

I am a mechanical engineering student looking to learn how to work on cars.

My friend has given me the opportunity to take his 1988 Mazda B2200 extra-cab 5-speed. When I drove it, I saw why. The catalytic converter has broken off, and apparently pieces of it are in the exhaust. Would it be possible to just replace the catalytic converter, or should I replace the whole exhaust?

Also while driving it, there is a weird problem. About 10 or so minutes after startup and driving, it starts bucking back and forth as if I was engaging and disengaging the clutch. Any idea as to why that is happening? Theoretically the truck could drive even with this problem, but I don’t think it’s safe or good for the truck. What should I do?

Sajeev answers:

It wasn’t long ago that I was an mechanical engineering student looking to work on cars. Hell, it’s way more fun than a semester of Thermodynamics, Solid and Fluid Mechanics! So what’s my advice? Join the Society of Automotive Engineers (SAE) as a student and join the local chapter in your college. The SAE chapter at the University of Texas changed my life, in a good way. And if you don’t have a chapter? MAKE ONE!

Oh wait…you wanted advice on the truck, not your career. My bad.

The first problem is pretty easy, replace the convertor. Or not: eventually the loose bits of honeycomb inside will stop playing Super Breakout with itself, exit stage left, and it still might pass an emissions test. If not, any exhaust shop can slap in a new one, and I just Googled one for $270 that’s a direct replacement. I am sure you college kids use Google all the time, why not for a sweet little truck?

The second one is usually a combination of a poor gear change technique and a lack of fuel. Or maybe too much fuel. Does it buck less if you give it more gas and take more time to let out the clutch? Problem solved. If not, I’d recommend rebuilding the carb, seafoaming the motor (at your own risk, see YouTube for reasons why), and testing the fuel pressure. Actually not in that order: start with fuel pressure, then maybe learn how to work on a carb.

Or convert it to a later-model EFI setup! Or even better, LS1-FTW!!! You are an engineer for a reason!

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

#B2200 #CARB #CatalyticConvertor #Efi #Engineering #Ls1-ftw #Mazda #SAE #SuperBreakout

Sajeev Mehta

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3 of 12 comments

Greaseyknight on Jan 23, 2012

The bucking almost sounds like the exhaust pipe/muffler is clogged with bits of the catalytic converter, and is creating alot of back pressure. We had a Nissan Quest that did something similar when hot, it got worse to the point where it wouldn't move. Took the exhaust apart and cleaned all the pieces out.

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- Fincar1 on Jan 23, 2012
  
  +1; same thing happened with my 1999 Accord when it had 150k or so miles on it. It had given a check engine light that I ignored because of a year's worth of spurious indications before that.
  
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Millmech on Jan 23, 2012

I had a Nissan truck, 1983, with a carb; anyway, that + a number of other 80s vehicles would "jerk off" if trying to coast with ANY amount of throttle. The only way to coast in gear smoothly was to take foot OFF the throttle. Having said that, something made the converter come apart; better find out what.

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