Piston Failure

Ronald Technical Support Specialist Trail, British Columbia Posted   Latest  
Question
Drivetrain
2012 Audi A4 Quattro 2.0L (CAEB) 6-spd (0B2)
P0303 - Cylinder 3 Misfire Detected
Low Compression
Broken Piston
Low Idle

Vehicle has 70 000 km (45 000 miles). Original customer complaint was check engine light on. Engine code was P0303. When vehicle was brought it was not missing and we road tested and could not make it miss. We moved the ignition coils and plugs and sent vehicle back out with customer.

A few days later check engine light returned and vehicle was running rough. Code was P0303 again but now the compression on cylinder three was close to nothing and leakage was through to crankcase. Further diagnosis resulted in disassembly of the engine to find a piston with broken ring lands. The top of the piston looks perfect. I am not sure the cause of the piston failure. Any ideas?

Vehicle was new to customer so know history. There was no indication of oil burning.

Looks like we are going to rebuild. There is the slightest of scratches in cylinder 3 bore but everything else looks perfect. The piston pieces we found so far were in oil pan and timing cover area. Before going ahead I would feel better if I knew what happened. The pistons are very thin under those lands on that side.

Thanks for any insight.

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Gail Technician
Garner, North Carolina
Gail Default
 

My experience has been detonation. So I would be looking a timing controls like knock sensors.

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Joseph Technician
Lexington, South Carolina
Joseph Default
 

Ronald, Looks a lot like low-speed pre ignition, I am by know means an expert or even well versed in the phenomenon but my guess is the engine didn't have a lot of correct spec oil in it during it's life, Although we have had a couple here that were serviced by the dealer and had the issue though at around 70-80k miles and came to us with broken pistons so I am not sure what they are using. Not…

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Randy Curriculum Developer
Raleigh, North Carolina
Randy Default
 

You’re right on target Joseph. The clue is the blown out ring lands. The root cause is not exact science but the results sure are. Correct oil formulation is the first line of defense. FYI... LSPI causes instantaneous autoignition that surpasses detonation pressures by 300% or higher. Hence the severe damage with little or no warning. I’ve seen dealers use aftermarket oil in bulk that was not…

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Scott Owner/Technician
Claremont, California
Scott Default
 

Ron stated that the service history is unknown but I would like to know the following in order to understand the pattern leading to these failures: - Oil change intervals - Fuel used - Typical Drive cycle - Service history / complaints Would these items follow your line of questioning?

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Randy Curriculum Developer
Raleigh, North Carolina
Randy Default
 

Agreed although I'd take a close look at oil type of available.

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Elias Owner/Technician
Poway, California
Elias Default
 

You may want to check and see if the pcm has been tuned...this is not super common but have seen before...good luck.

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Ronald Technical Support Specialist
Trail, British Columbia
Ronald Update
 

The consensus seems to be detonation. In looking for images of pistons with broken ring lands a lot of turbo (tuned) Subaru pistons show up. The ring lands that break are on the side of the piston parallel to the pin. I figured that would be similar if it was detonation in my case. I thought the slapping of the piston would be along the faces parallel to the pin and thus the ring land might be…

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Brendan Owner/Technician
Browns Plains, Australia
Brendan Default
 

We see quite a lot of this LSPI ringland damage in Australia, likely due to our fairly low quality fuel by Europe Standards. The worst offender I would say is the 1.4L VAG twin charge engine used mainly by VW. Sure it won many international design awards upon release, but a quick google search will show its inherent flaws with detonation - there is an extended dealer goodwill warranty on this…

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Ronald Technical Support Specialist
Trail, British Columbia
Ronald Update
 

Thanks for all the info. Did a bit of research on this LSPI. A further question I have. We are going to replace pistons and rings in this vehicle. The OE procedure says nothing about honing the bores when replacing rings. The dealers do a lot of piston and ring replacements in these vehicles for oil burning. They do not hone the bores. I am not sure about this. Any insight on the…

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