dumbfounded on cylinder #6 misfire

mhicks · June 13, 2023

Hello everyone. I have a 2013 Silverado 2wd with a 4.3 v6 and it's coming up with a cylinder #6 misfire code and dumping enough white smoke to make a pest control company jealous.
I have replaced the plugs and wires (wasn't smoking then) and it ran great for all of about 36hrs before coming back with the misfire. Still no smoke signals at the time, so I replaced the Ignition coil and all seemed well for about another 24hrs before it started releasing it's mosquito repellant and misfiring again. I have replaced plugs, wires, ignition coil and the complete spider injection system and it still plagues me with smoke and a miss. What am I still missing to check? I have ran 3 different compression tests and nothing has showed below 142psi on any cylinder. Could it be an issue with the PCM? I've never ran into this issue before and any/all information is appreciated! I don't have the diagnostic equipment I would like to have, but I'm trying to save myself from paying for a potential mis-diagnosis or any more "swing and misses". Thank you all and have a great day!

asilverblazer · June 13, 2023

New parts doesn't guarantee good parts.

Try swapping one component at a time from the bad cylinder to a good cylinder. Plug, wire, coil, etc...

Have you checked compression in its current state? Might have ran too lean too long and burned a valve...

If it is indeed ONLY cylinder 6, and the above 'external' cylinder specific items aren't the culprit, then its an internal engine issue...

For the sake f being thorough, I'd through a vacuum gauge on it and spark tester.

Bleepster · June 13, 2023

isn't white smoke indicative of a coolant leak - AKA blown head or intake gasket?

mhicks · June 13, 2023

1 hour ago, asilverblazer said:

New parts doesn't guarantee good parts.

Try swapping one component at a time from the bad cylinder to a good cylinder. Plug, wire, coil, etc...

Have you checked compression in its current state? Might have ran too lean too long and burned a valve...

If it is indeed ONLY cylinder 6, and the above 'external' cylinder specific items aren't the culprit, then its an internal engine issue...

For the sake f being thorough, I'd through a vacuum gauge on it and spark tester.

At one point, I sold auto parts and can sadly confirm this statement to be true.

I have done the swapping around on the parts prior (after checking the tip of the spark plug) to the tune-up with no indications of the misfire moving cylinders. It does have the newer one coil pack design vs the individual packs. It ran for all of 2 minutes after installing the new spider injection system yesterday before the smoke came back. I did run the compression test again afterwards and it had only dropped to 140. I have yet to check it with a vacuum gauge, but it does have good spark.

newdude · June 13, 2023

2 hours ago, mhicks said:

Hello everyone. I have a 2013 Silverado 2wd with a 4.3 v6 and it's coming up with a cylinder #6 misfire code and dumping enough white smoke to make a pest control company jealous.
I have replaced the plugs and wires (wasn't smoking then) and it ran great for all of about 36hrs before coming back with the misfire. Still no smoke signals at the time, so I replaced the Ignition coil and all seemed well for about another 24hrs before it started releasing it's mosquito repellant and misfiring again. I have replaced plugs, wires, ignition coil and the complete spider injection system and it still plagues me with smoke and a miss. What am I still missing to check? I have ran 3 different compression tests and nothing has showed below 142psi on any cylinder. Could it be an issue with the PCM? I've never ran into this issue before and any/all information is appreciated! I don't have the diagnostic equipment I would like to have, but I'm trying to save myself from paying for a potential mis-diagnosis or any more "swing and misses". Thank you all and have a great day!

White smoke strong enough to make a pest company jealous?

Heavy white smoke sure isn't a sign of a bad coil, spark plug or injector, and I'm sorry to hear you dumped money on plugs, wires, coil AND new fuel injection system. That is an almost sure sign of coolant getting into that cylinder.

Its either a bad head gasket or the intake manifold lower gaskets are leaking. The intakes on these old 4.3s are "wet" intakes, coolant does flow through them unlike the newer engines which are all "dry" intakes.

A block combustion gas detector can be used to sniff out combustion gases in the coolant which could indicate bad head gasket. A cylinder leakdown test is something worth doing as well.

Edited June 13, 2023 by newdude

dna9656 · June 14, 2023

After reading what the guys (that know more than I) say I'd replace the head and intake gaskets.... Now that means taking the intake and the heads to the man (machinst) and getting the heads and intake made true, square, tangent, and congruent; IOW square and true! then put the ucker back together In Accordance With (IAW) Chevrolet.

asilverblazer · June 14, 2023

I must've missed the WHITE smoke part... Not real positive, but a good compression test suggests coolant entering the air intake tract between the valves and throttle body. An internal leak/crack in the manifold, or, if you're lucky an intake manifold gasket.

swathdiver · June 15, 2023

White smoke, you blew a head gasket.

KARNUT · June 15, 2023

You could always try a stop leak product. I bought a used car once that I did a coolant flush. Shortly after it wouldn’t turn over. After pulling the plugs and pumping the water out, I added bars leak fixing the problem. My 02 avalanche has the famous head crack problem. It leaked into the oil after shutting off. The water stayed at the bottom of the pan never mixing with the oil. Bars leak fixed that going on its second year. I’ve had three vehicles so far that had leaks that bar’s leak have fixed. There’s even stronger products that fix even the worst of leaks. If nothing else it would point to the problem by eliminating the problem. Then you can make your decision.