2008 avalanche 5.3. Have had lots of ses codes happening. Here's what I've replaced. Water pump, fans, radiator, t-stat, temp sensor, exhaust manifolds, gaskets, entire exhaust to include O2 sensors, mass air flow sensor,map sensor, purge selonoid, fuel pump, plugs, wires, fuel injectors, coil packs, intake gaskets,oil pressure sensor. All OEM or quality parts store parts. No cheap eBay crap except for two refurbished ecms.
Here is where I stand now:

1st ecm (original) gives codes p0175 and p0172..no misfire p0307

2nd ecm (refurbished)eventually gave p0307 and would not finish last ecm test

3rd ecm (refurbished) ..
Drove about 60 miles and turned around and came back home. Wasn't until halfway back that it gave a pending p0307, then changed to pending p0300. Never an engine light came on. And, it didn't complete not one single ecm test the whole trip. And, I made it there and back on less than a quarter tank.

Any thoughts?

 

Are you throwing parts at this thing for a reason? What are the symptoms?

I dont see in your list: knock sensors

I'd do a compression check and see if the misfire is compression related or if it's in the ignition side

then I'd move coil around and see if the problem follows the coil

most everything you've replaced has nothing to do with misfires, so I'm a little concerned as to why the parts cannon was fired at this thing

 

I have replaced plugs, wires, and coils. I plan on keeping this for a very long time, so I have no problem throwing parts at it. But would like to keep it from going to the money pit dealer. Lol I had other issues with O2 sensor codes, so I just replaced everything. The water pump went out a while back, so I replaced it and all cooling related parts. I read that a bad temp sensor could cause rich codes, which is what I get with the original ecm. But now it seems that the two different ecms are pointing me in different directions. But you are correct, I haven't replaced the knock sensor yet. I just replaced the intake gaskets and was expecting to see two of them under there, but apparently mine is on the side.

 

The only symptoms of a problem are the sea light and poor gas mileage.

 

I'd do a compression check and maybe move that injector to a different cylinder to see if it follows.

Cylinder 7 is a AFM/DoD cylinder as well so it's possible it's something with the lifter or the camshaft lobe being partly wiped out.

 

Didn't even think about AFM/ DoD

 

Thanks for the info. Will check compression this week. May disable afm just to see if it helps.

 

No offense intended whatsoever but why in the heck didn't you get a pro to diagnose it? I stick to **** I'm an expert at and hire the other stuff done which is a lot lol.

 

wont help if the valley cover is leaking or the lifters are failing

 

No offense taken..lol. I'm not as fortunate as many to have "pros" that I would trust touching my truck. Every single shop here in Gainesville FL that anyone has highly recommended, has screwed something up on my truck.
Here are a handful of simple things that the local pros have done to me.
Not rotating directional tires properly
Replacing the shield on the top of the engine and completely crimping the return coolant hose from the heater core.
Not putting center caps on the wheels properly so they fell of within a block of leaving the shop.
Not installing swaybar endlinks properly so it's just metal on metal.
Not replacing the entire upper control arms like I requested because they said ball joints we're still good, although bushings were shot and made ungodly creeking sound going over speed bumps.(my money, just replace what I want replaced)
Adding stop leak and trying to say they replaced rear main seal.
That's just on my current vehicle. I could go on about my other cars.
If you want something done right, do it yourself. If you don't know how to do it, learn it! That's why I'm here.