Broken exhaust valve

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So i have my Seat Leon Cupra for like a month or 5. It has a Golf 6 R20 engine ( engine code CDL, EA113 2.0T FSI k04 ). I was driving it on the autobahn in Germany, accelerating hard to 250 km/h, had to let go off the throttle for another car and when i went back on it, after a few seconds the power was gone and CEL starts flashing. didn't hear any pinging/detonation during the drive. Thought of a broken coil and limped it back to the garage where i work on saturdays. VAG-Com said misfire on cylinder 4, so replaced all 4 the sparkplugs and coil packs. when i screwed out the sparkplug of cyl 4, i noticed that it was in bad shape. After putting in new plugs an coils it did still run on 3 cylinders and it was still misfiring according VAGCOM. So pulled out the plugs and did a compressing test. ZERO compression on cylinder 4. Took a look with a boroscope and the exhaust valve looked broken, so it will be a head job what i'll need to be doing Any thought on what have might happened? My car was mapped 2 weeks ago, and my tuner ( a very respectable company over here ) drove more than 100 miles on the road and dyno and said that it was finetuned perfectly. Stage 2+ custom map, 367 HP/470NM Torque Autotech HPFP Audi S3 intercooler HG motorsport intake HG motorsport turbo outlet Miltek turboback exhaust with 200cells cat BSH PCV revamp kit Go Fast Bits diverter valve + Had RON100 octane in the tank, wich is the same as AKI -+ 95 Thought on this?
 
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Detonation. Someone screwed the pooch but the chances anyone will will admit to it are slim and none. I would be looking carefully at the piston and rod also.
 
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Tommiee

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Don't know yet, have to take off the head to take a good look. Trav, my company does big business with these guys ( chiptuning, DPF removal, EGR off and many other software mods ) If they [censored] this up they'll lose us as a customer probably, don't think they wanna lose that since we're bringing them a LOT of work. But ofcourse it might. I did contact them, they say that it is probably due the bad spark plug, and it would have gone too without the tuning, maybe a week later but it did. They offered to dyno and rolling road check the car again after i fixed it to exclude any detonation and lean conditions.
 
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How's your fuel system? Is it a dead head (return-less) setup? If it is return-less, and #4 is the last on the rail, start looking towards the fuel system, (rails too small, fuel pump failing or too small etc.
 

Tommiee

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Will do Rshaw125, no cylinder/piston damage was visible with the boroscope, but will only be sure when the head is off. If it is damaged, i will go the right way and will replace rings and hone. new pistons if needed.
 
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Also, how is it cooled? If #4 is the furthest from the water pump (last to be cooled) often tuners will adjust for hot cylinder with individual fuel trims. The last cylinder to be cooled (the hottest) should run a little more Fat than the others at WOT.
 
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Tommiee

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My knowledge of software tuning doesn't go that far Tman 220.. so i honestly don't know. These engines normally don't have any cooling or knock problems when tuned, they're used in the S3, Leon cupra R and Golf R20. it's basically a reinforced MK5 gti engine with a different head with sharper cams, stronger rods and pistons, k04 turbo instead of k03 and bigger injectors.
 

Tommiee

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it's typical that only Cil nr. 4 had this strange buildup on the plug, the others looked perfect. makes me thing that the plug electrode was bad for a long time and it didn't fire well making it foul. it does use some oil, maybe it'll have to do something with it.. we'll see..
 
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Originally Posted By: Tommiee
Don't know yet, have to take off the head to take a good look. Trav, my company does big business with these guys ( chiptuning, DPF removal, EGR off and many other software mods ) If they [censored] this up they'll lose us as a customer probably, don't think they wanna lose that since we're bringing them a LOT of work. But ofcourse it might. I did contact them, they say that it is probably due the bad spark plug, and it would have gone too without the tuning, maybe a week later but it did. They offered to dyno and rolling road check the car again after i fixed it to exclude any detonation and lean conditions.
"Bad spark plug" is too simple an answer.
 

Tommiee

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Agree with you there herrstig. Don't know yet if the valve is broken or burnt. A friend of mine is a mechanic and will help me pull the head and fix it. He is coming back from vacation next week.
 
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Is it possible if you tune that the gaps were played with a lot in the past weakening the plug electrode? When weakened, under high RPM it breaks off, and that little piece of metal loose in the combustion chamber could break a valve but hey, it is a guess. I would inspect the valve seat and see if it got embedded there or chipped it and the valve.
 
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Tommiee

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The german, that's exactly what i think what happened! Any suggestions what to replace maintenance wise? Valve seals ofcourse, timing belt and water pump. Any further?
 
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Detonation. It has aluminum bits embedded in it. It may well have started with the plug. I've seen exactly the same thing, melted the piston in my case. It appeared to be caused by a sparkplug, too hot and wrong style. This was back in the 60's, but still relevant.
 
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3-Way valve job (if that lingo still exists and applies to your valve geometry), machine the head flat and any PM stuff that is bothering you do it at the same time is pretty much it. Valve seals for sure. Viton does wear then you get the pita morning puff of smoke that isn't great for the CAT but you are already there, do it it is cheap as the labor is saved big time. Valve cover gasket is a no brainer but you'd be surprised that many people try to reuse it. As far as "heart surgery" is concerned this is easy stuff you didn't damage much I'd guess. It is a setback but this is nothing to worry about too much. You PM list sounds great you know your stuff, the rest is budget. If that seat accepted that hot metal nugget, the Valve will hammer away on it until it shatters. AGAIN, I am guessing.
 
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^Yes the rust is confusing to me. I am under the impression tuning would involve a lot of indexing etc so why rust. Maybe not a great tuning shop to tune on ancient plugs?? I am hoping pic city of the valve seat if it is notched or still has the plug piece embedded in it.
 
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Tommiee

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Great forum this is. Helpfull reactions! Ofcourse i will shoot some pics, i have a boroscope picture too, but it is difficult to see on a picture made of the screen of the boroscope Ignore the date, it's off.
 
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