I have a 2008 Tahoe Hybrid with 93K miles. Took it in yesterday for a misfire (P0300) and after some research they found a Tech Bulletin on the issue. The valve (#4 in my case) was letting in too much oil. This was a GM warranty issue, so did not have to pay for anything other than an oil change, as my oil was about a quart and a half low.
EDIT:
From the Repair order: 93391 P0300 eng miss fire detected. found sparkplug cyl1 oil fouled. replaced Valve Rocker Arm Cover and spark plug. J7576 1.2 per bulletin 12-06-01-001B
Parts and Labor 237.46 (warranty item)

If you are having the same issue, have your mechanic look for the bulletin above. My car is running smooth again!

 

Thank you all for the great info. Have not been on the forum for a while but am still loving the Tahoe. The issue I was having with misfire notifications went away after I used Chevron Techron fuel additive.... I can't believe it either but I kid you not that stuff works. Not sure that it did but perhaps cleared out some gunk in the fuel line that was causing improper firing. I buy the stuff by the case now and use it almost every other fill up.

 

Techron fuel additive.... I use ONLY chevron in all my fuel injected cars and I have never had a fuel related issue, its great stuff!

 

Techron, it works. Years ago BMW used to recommend it as regular maintenenance for it's M cars, I've been using it since and never had a fuel related issue that I can recall. They sell it by the case at Costco in my area. Chevron puts a small amount in the Premium Gasoline they sell at their stations. Also, I think it's important to only use "Top Tier" Gasoline, it's higher grade gasoline with a better detergent concentration level.(Google Top Tier Gasoline) Modern Internal combustion engines have very tight tolerances and even a "booger" on top of a piston can wreak havoc with the computer.

 

I have a 2009 Tahoe Hybrid that had 2 cylinder misfires. Changed the spark plugs (it was time anyways) and changed the coil packs on Cylinder 1 & 2 ( super simple). Here my video of me changing the coil pack on cylinder 1.

 

don't use BP they have garbage gas i had bad luck with them.....

i had a oil fouled #1 as well I have been using M4 and have not had an issue make sure you turn on the A/C so the battery does not overcharge/overheat.... while in M4

also resonantly i had an issue with #6 that would misfire on cold (just one single misfire..)start up I ran lucas fuel injector cleaner 16 oz in 25 gallons it helped quite a bit.. no more misfire on that one..

I have not had any CEL so far or misfires
The engine is no longer violently shaking at idle the vibration is different and pretty close to my 4.8L truck i had before..

 

after buying a new motor I decided to dig deeper into the original and I think I found the misfire issue. 2 bend pushrods... like noticeably bent

 

So Dustinlint can you tell us more about this new engine?. Is it a GM crate engine / used low mileage unit or maybe a reman engine? How much? Several people seem to be driving some high mileage Two Modes that might gain some insight on what to do if their very tired engine finally gives up the ghost. I am milking this 265k unit for all it is worth but I know that it probably does not have many more miles before it has a major failure. Would appreciate you sharing your experience. Tks

 

I should of been more clear. sorry. I got a junkyard motor for $500. 180k. installed lifter tick...ripped it back out parts come tomorrow. i looked and looked for a new motor. couldn't find. Short on cash but its becoming expensive! Imo just keep the motor you have rebuild it before its too late. bore/sleeve everything if money isn't an issue lol. when i pulled heads off old motor I couldn't believe how much carbon build up there was. the task itself for removing the engine could of been easier, I couldn't find any writeups. The motor mounts are a royal pain. save yourself the time by "getting stuck on stupid"
1.remove front bumper cover/hood/FENDERS!
2. remove engine fluids
3. remove engine intake and exhaust manifolds.
4. remove heads
5. remove bell housing bolds and tor conv bolts.
6 remove motor mounts.
7 remove block
8 rebuild
9 reverse instructions
10 fill ac with r134d that doesnt have oil or stop leak in it (mistake will be costly)
11. if swaping any modules a maxiflash is required.

some people choose to delete the AFM. by swapping out the cam and using traditional lifters. I however have chosen to KEEP AFM. the cost was more but here in portland gas is about 550-625a gallon so I will keep the AFM

 

good info on getting the engine out the easiest way. if you happen to have a head off one, can we get a pick of the tops of a piston. I'd be curious if it's higher compression than a standard 6.0 pistion. if you can even tell


I think keeping the afm was probably the easiest route to make sure it works. these engines have a odd ball cam, I think they call it late intake valve closing. Ackerman cycle or something like that, it makes the engine more efficient at like 2k-3k rpm but at a loss of off idle tq. in hybrids it works because the electric assist off the stop and increase fuel efficiency at cruise. the delete afm cams that I've seen are for the standard intake timing non hybrid. so you'd need something custom grind. from what I understand you can't run non afm lifters on the lobes designed for the different afm lifters. I've got hp tuners, looking thru it and a reply to a question on their forum leads me to believe there's no way to tune the ve tables in this ecm like you can a more mainstream one when you change cam shafts usually just a little more lift and duration to move the power band up, ours it seems would be more complicated on the tuning change requirements. there's PE tables, basically wide open throttle fueling. but I didn't see anything about the time spent in closed loop like idle and part throttle area. I asked if they thought the computer would have enough room to self adjust for it, but got no reply. so I do believe the safest thing is to keep the same cam design in our trucks. oddly there's dodge aspen suv with this hybrid system, same tranny, battery and all with a Hemi that doesn't use the late intake closing cam. it is rated at less mpg and I don't know if they do v4 mode, probably not. but I've been curious how they drive with all the off idle tq and the hybrid kick. probably an enjoyable to drive truck.