Piston Slap: Earth Dreams of Carbon Buildup?
TTAC commentator KCFlyer writes:

Dear Sajeev,

I have a 2015 Honda Fit LX manual, purchased new. From day one I noticed a slight momentary hesitation under moderate acceleration when the engine was cold. I took the car to the dealer after a few weeks but they could not duplicate the problem. I dropped it off again and left it overnight, hoping a cold engine would allow them to experience the issue. No luck.

Fast forward 57,000 miles. Same problem persists and is reported to dealer via phone several times. The check engine light comes on. Dealer says the code means an #3 cylinder misfire. They say the fuel injectors are clogged and charge $1,300 to replace all four injectors. Honda of America throws in $1,000 of goodwill money because fuel injectors are not covered by the 60,000 mile powertrain warranty.

Two weeks later light comes back on. Same code. This time another dealer pulls the head and finds carbon buildup on all four piston heads. They clean up the engine, clean the throttle body and declare the vehicle fixed. Total charges paid for by Honda of America under goodwill claim except $217 for the throttle body cleaning. That was yesterday and I will know within days if the original problem persist.

Tech rep was awesome. He recommends I get the fuel injectors and throttle body cleaned every 30,000 miles. My question, what caused the carbon buildup? Does the buildup damage the engine even if later cleaned up? Should I dump the Fit? It is an awesome commuter. I average 44 mpg summer and 39 winter.

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Piston Slap: Bustin' Carbon Down Mexico Way!

TTAC commentator cacon writes:

Hello Sajeev,

I’m a long time reader, but not much of a poster. Anyway, I currently own a 2009 SEAT Leon (bought new, I’m from Mexico if you wonder how I got this car), which is basically a 5th gen VW Golf in drag, 1.8 TSI engine and 6 speed manual, 32k km in the odometer (about 20k miles) almost 100% of city stop and go traffic. Currently, there’s nothing wrong with the car, but today I took it to the dealership for the vehicle emissions tests (all good) and looking at all the services that they provide I found this: Engine Carbon Build Up Cleaning with Hydrogen, so I ask the service representative what it was, in he basically told me that a machine is connected to the fuel system of the car and they feed it with hydrogen and keep the car running for about half an hour, and that should remove all the carbon build ups in the system.

Reading this and other forums I learned about the propensity of major carbon build in the valves, regarding the direct injected engines, so I found this interesting. Googling this cleaning system, I rapidly found about it: OxyHydrogen Engine Carbon Cleaning, although I just barely read about using it in scooter engines.

Then it came to me!! Ask Master Sajeev about it!! So I’m wondering if you ever heard of this system and if it’s really effective in removing carbon build ups, or if it is a bad idea to ever think about it. Dealership charges about $50 to perform this service by the way….

Saludos desde México!!
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