I have a 06 ss Monte Carlo 5.3 with about 90k miles I'm getting a misfire cylinder 4. Good plugs, coils, plug wires, and good injectors. So what should I check next? My engine light flashes when I accelerate it smokes white at idle after about 10 minutes of driving. Hoping not a blown gasket.

 

White smoke is water/anti-freeze burning off. I would advise taking the plug out of the #4 cylinder, see what it looks like. It may tell you a big clue to what's going on. You can compare it with other plugs, see how they all look. You can also conduct a compressing test and see if a cylinder is loosing compression.

But the smoke from the exhaust is not very promising.

 

Im curious,
Are you using/loseing Anti-Freeze? Does the Motor run hot? Is the Number 4 plug discolored when you removed it? Does it smell other than of gasoline?
These are all signs of a possible leak/headgasket.... The white smoke after idleing for 10 minutes does the exhaust have a "sweet" smell to it?

If you pull off the oil fill cap...does it have a milk shake color around the edges/or inside the valve cover? Is it low on oil? or overfull? Is there a milk shake color on the dipstick?

I would also recommend do a pressure test on the cooling system.

I would do a cylinder leak down test on the #4 cylinder.

I do know in 2003 and 2004 Chevrolet used a substandard heads on the 5.3's .... They were known to develop small cracks in the top of the head
near/around the valve guides... Thus causeing a coolant leak ... and cylinder failures.

I'm not saying you have a cracked head... But anything is possible.
I hope this helps...Please get back with us and let us know what you have found out...and or how you fixed it.
Thanks for joining the MCF Family.

 

Hopeing your making progress and looking forward to your resolve.

 

There is a problem on the LS4 related to oil blow-by caused by the DOD system. Are you burning any oil? Also, here is a site with some GREAT info.

LS4 FAQs - LS4 Store

 

So I just found time to take it apart. I got to taking off the manifold all ports are dry except cylinder 4 that was misfiring was filled with gas any suggestions

 

So I just found time to take it apart. I got to taking off the manifold all ports are dry except cylinder 4 that was misfiring was filled with gas any suggestions

 

Well it smelled like gas

 

Possibly a failed injector leaking gas in the cylinder. Or a spark plug not firing or firing with weak spark (could be plug, wire or coil). My two best logical guesses.

 

New plugs, new wires, coils good, injectors good