Hey guys. I have an 09 SS/TC —> LDK that recently threw a cylinder 3 mis while driving on the freeway at ~85mph. It runs 50/50 E85 and 91 gasoline.

I did a comp test on it: cylinder #1: 130, #2: 130, #3 0!, #4: 145
I did a leakdown, which showed pretty much nothing. Cylinder 3 has 10% leak, all other cylinders less than this.

under the hood, the engine sounds fine. Doesn’t sound any different than it ever did. Down by the exhaust pipe, it sounds like trash. It’s almost like a sputtering sound but loud, maybe like a diesel truck. It intermittently puts out grayish white smoke. Not really blue and not black.

At first I thought maybe valves, valvetrain worst case rings, but after not getting a whole lot in the leakdown idk. Anybody have ideas or more diagnostic I can do myself before taking it in to a shop?

should add that I’ve replaced the spark plugs and coil packs already.

 

That is odd. I'm not even sure where to start on that one. How many times did you run the compression test on #3?

 

We ran it 4 times. A solid 0 every time. And the ONLY code it has is for the cylinder misfire. I can’t imagine fuel being the issue for one cylinder having NO compression. I buy from a reputable vendor. But I may drain the fuel lines and refill just to see what happens.

 

Remove the valve cover and make sure the rocker arms didn't fall off. Normally it takes a money shift to make them fall off, but I'm sure load and higher rpms could cause it as well. If the rocker arms fell off on the intake side it would register a 0 psi on compression but pass leak down.

 

I didn’t think about that, an easy thing to check for, too. I will check that, thanks for the suggestion!

 

Interesting. I've had them come off on the exhaust side, but that was actually because my lifters collapsed since the spring pressure required to open the valve is so much higher.

That was also at 8200-8300 rpm.

 

joys of LNF life, one or two money shifts or bounce off the rev limiter and it heads out. Normally you can push them back into place without removing the cam.

 

White smoke = coolant in combustion chamber
Bluish smoke = oil in combustion chamber
head gasket?

 

+1

That does make sense. Would explain why 0 compression but passes leak down.