Rough idle / cylinder 6 misfire help needed

kudos1111kudos1111 Member Posts: 1
edited November 2015 in Chevrolet
Motor is 4.8 and 120,000 miles

Ran into an issue just last week where it started to run at a rough idle, especially while in drive coming to a stop. It coded and I had a mechanic friend of mine hook up his reader and it said a misfire on cylinder 6.
This is what has been checked and or completed.
- replaced spark plugs/wires
- put fuel/injector cleaner in it, seafoam (I believe) and ran 2 tanks of high octane fuel through it.
- cleaned air intake
- switched coils around (no change still #6 misfire)
- swapped plugs and wires (no change)
- checked compression and was exact with specs and checked another cylinder as well just to be thorough all the same
- checked fuel pressure just to say we did even though this should result in multiple or random cylinders misfiring as well as air intake ( all spot on)

Fuel filter is in tank with pump but it shouldn't be either, pressure was spot on and as stated before it would code out multiple/random cylinders, not just one specific.

Now here is the kicker, before this all took place, I had shop check my transmission fluid and told them to top it off if indeed it was low because I had noticed a hard shift from 1 to 2 just a few times, it only happened when it was in the morning only at the first shift and then never again.
They did say it was a little low and it was topped off, didn't happen after that.

Then a few weeks later I had the code and misfire.

Now, I have noticed the hard shift on occasion again, and a new development a weird knock that occurs during the middle to end of the gear cycle from 1st to second and 2nd to third. Never through the whole range and what's even weirder than that, it doesn't occur consistently, it will happen and then the next stop and go it will be as silent as before, both with and without the rough idle is always there.

I can notice the misfire while driving as well but not by much at all, only when overdrive kicks in and try to save gas then sometimes it gets more noticeable but not every time is it like that.

Took it out and punched it a few times, no loss of power during that time sounds clean and pulls hard but would start to chug a little at idle afterwards.

We are convinced its the fuel injector but that was before I started to get the on and off again knocking and hard shift, both are inconsistent and never constant.

So, hopefully someone has been there and done that and can help or give some major insight.
I have not been able to locate this issue entirely on any forum on any sight.

Any and all help will be greatly appreciated. Thanks in advance!
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