alright so my completely stock 2008 cobalt l61 kept popping a cel at 33000 miles so i took it to the dealership but the cel light came off of course the day before and they couldnt detect a hard code. fml alright so i had to wait for it to come on again, next monday it came on again but i couldnt get it to the dealership til saturday. started the car up to head out and it didnt come on, took it anyway and they actually detected a code this time not sure which one, so they did a compression test and found one cylinder to be a little low and found a burnt valve in the head. my question to you guys is what possibly could cause a burnt valve because my dad thinks its from me beating on the engine. i didnt really beat on it a crazy amount and the engine only had 33000. i mean i drove spiritedly getting up to about 4.5k once or twice every trip but i RARELY took it all the way to redline or did long pulls or anything. does anybody have an argument that it was not due to beating on the engine and why? what is common with these cars that could have caused it? or am i just trying to get out of things and it most certainly could be from beating the engine? any input would be appreciated

thanks in advance

 

The most obvious answer is the fuel you used. I.E. most of us use oxygenated fuels (contains 10% or m ore ethanol) the problem lies when you have clogged injectors and a fairly high compression engine. Pretty easy to burn up a valve. IF the spray pattern comes out as more of a dribble than a cone...

There's not many other ways, and the above is incredibly unlikely, so I would say you were beating on a car that couldn't take it anymore.

 

#1 reason dirt on seat..

#2 lean running condition..

#3 timing out of spec..

 

i read up about it online and saw absolutely nothing about wot causing it either. for gas i always use the big names (7/11, bp, mobil, racetrac) but ill make sure i look for the 10% grade in the future. hopefully it isnt from the engine running lean, but hey i got powertrain for 27000 more miles haha

thanx for the help!

 

The couple of Ecotecs where I've had to deal with compression loss and misfires didn't end up having burnt valves. It was more like a valve-seat issue. Something similar to the manufacturing issues GM had with the inline 5 and 6 cylinder engines. The solution in all of the above has been a new cylinder head assembly.

What caused it? I haven't the slightest idea. Possibly what Greywolf is saying. I've seen more cases of higher alcohol content in fuel recently. GM's standard is 10% and below ethanol content unless the vehicle is equipped for flex-fuel. From what I've been hearing, the government is now mandating up to 15% alcohol content in fuel. Things may start to get interesting with all the lean codes getting thrown around.

 

well one other possible thing i was thinking was picking up deposits in the gas tank. i always drove with barely any fuel, idk why, maybe as an incentive to get good gas mileage but i would only put $5-10 dollars in the tank and run it all the way to empty and repeat. could it have possibly picked up the dirt and caused a dirty valve seat? idk, really werid. the dealership said they have never seen it on a stock cobalt...

 

While running your car low on fuel like that may shorten the life of your fuel pump, I'm not seeing alot of sediment getting through the filter sock and fuel filter. The fuel filter is external so if that's a concern of yours, maybe you should replace the fuel filter.

For something to get through the filter it'd have to be in solution with the gasoline. Sugar, for example.