Cylinder 7 misfire caused by flaking lifter chrome

[Uscgevo]

There's a bunch of guys on here from Miami and surrounding parts. Let's hope they chime and get over to your place to help out.

That would be rad. I could use a little help with this one. I am really kind of at a dead end now. Could the VVT system cause it?

 

[swathdiver]

I don't think so. It has to fuel, ignition or hardware related. Bad Injector, Bad Coil, Bad Wire, Bad Plug, Bad Spring, Bad Spring Keeper, Bad Valve, Bad Head Gasket, Bad Piston, Bad Ring, etc. How about an intake leak on that cylinder? A failing AFM lifter will cause misfires too.

 

[Sgtduckyboy]

The engine is a 6.2 in a Yukon Denali without AFM or cylinder decactivation I have done lots of research and have looked into the typical causes. Here is a list of the things checked and replaced:
-Compression checked good
-No play in rocker arms at multiple crank positions
-Swapped in multiple coil packs, checked coil pack harness with a meter
-New injector, plugs, wires, camshaft sensor, crank sensor
-Swapped the new injector to another cylinder to rule out a bad new part.
-HP tuner software killed the injector and it got worse

I am really at a loss with this one. Car seems to run fine. No power loss I can tell. Gas mileage seems to be normal, 13-17mpg depending on driving. Not sure what else it could be and I don’t suspect the lifters as I have no play in the rockers. Please help and let me know if you have any ideas or other checks I could. Wish my first post was under happier circumstances. Thank you in advance for the help.

Not to scare you, but do you have any 'ticking' noises? I had the ticking noise from around 4 or 6 mostly under heavy load or old oil. a fresh oil change would remove the ticking for about 100 miles. Then one night, my misfire warning started, 2 hours later, seized exhaust lifter in 6.

 

[Uscgevo]

Not to scare you, but do you have any 'ticking' noises? I had the ticking noise from around 4 or 6 mostly under heavy load or old oil. a fresh oil change would remove the ticking for about 100 miles. Then one night, my misfire warning started, 2 hours later, seized exhaust lifter in 6.

I did have a ticking noise, changed the oil and it has subsided almost entirely and definitly to the point my friends all say it sounds like normal valve train noise. The check engine light came one while idling but I don’t get the flashing misfire indicaton at all. I am at the point where I may just need to pull it all apart to see. Because I haven’t been able to find anything following all of the normal trouble shooting paths.

 

[Uscgevo]

I don't think so. It has to fuel, ignition or hardware related. Bad Injector, Bad Coil, Bad Wire, Bad Plug, Bad Spring, Bad Spring Keeper, Bad Valve, Bad Head Gasket, Bad Piston, Bad Ring, etc. How about an intake leak on that cylinder? A failing AFM lifter will cause misfires too.

Do you by chance know if I can use the lifters out of a LS7? They are the same diameter just not AFM, but since my engine doesn’t have that feature I figured it would be a failure proof replacement and the are a 1/4 the price.

 

[swathdiver]

Yes, using LS7 lifters is done all the time, 12499225. The regular lifters are 12648846.

As posted earlier, I learned that L92s had AFM hardware but was not active. I found a caveat tonight at Summit Racing's website that this applied to engines assembled before April 1st, 2006. So if your valley cover is flat, you don't have that stuff.

 

[Uscgevo]

Yes, using LS7 lifters is done all the time, 12499225. The regular lifters are 12648846.

As posted earlier, I learned that L92s had AFM hardware but was not active. I found a caveat tonight at Summit Racing's website that this applied to engines assembled before April 1st, 2006. So if your valley cover is flat, you don't have that stuff.

Took it apart and found the problem. The chrome on the roller of the lifter flakes and departed the lifter creating a low spot on the lower. Replaced all the lifters and now it is good to go. Luckily no damage to the cam lobe. Thank you for all of the help.

 

[swathdiver]

Great news Chris!