2008 Tahoe 5.3L Flex P0300 Help

[JimTahoe]

Is the KN a wet filter? Those can dirty the MAF and skew what the MAF reports.

Using 85 octane -- not that it matters but are you at a fairly high altitude?

I mistyped that one. It should have been 87 octane. I ran E85 in it a couple years back for two tanks and the mileage dropped.

 

[Fless]

I mistyped that one. It should have been 87 octane. I ran E85 in it a couple years back for two tanks and the mileage dropped.

Yes, the mpg will drop with E85 but it's higher octane at a lower price. And it can help clean the fuel system. I run it 100% when available, which is always around home and sometimes on the road.

 

[donjetman]

17% less energy in e85 than unleaded, thus the mpg drop.

 

[Geotrash]

17% less energy in e85 than unleaded, thus the mpg drop.

The same could be said about how I feel in my 50's vs my 40's.

 

[donjetman]

The same could be said about how I feel in my 50's vs my 40's.

Wait till you hit the late 60s

 

[JimTahoe]

A quick update for the group.. I found that the oil fill tube was broken and causing a vacuum leak in the right bank. That cleared the P0300. I was then getting misfires in #3 and #6. I played with moving wires, coils and plugs and found a bad wire on #3. #6 keeps misfiring. I bought a Bluetooth obd2 that comes tomorrow to help narrow down the issue and get you guys better data. Thanks for the help so far.

 

[Geotrash]

A quick update for the group.. I found that the oil fill tube was broken and causing a vacuum leak in the right bank. That cleared the P0300. I was then getting misfires in #3 and #6. I played with moving wires, coils and plugs and found a bad wire on #3. #6 keeps misfiring. I bought a Bluetooth obd2 that comes tomorrow to help narrow down the issue and get you guys better data. Thanks for the help so far.

Progress!

 

[JimTahoe]

Still no progress on solving #6 misfire. Fuel system stays in open loop due to system failure. Here are some numbers.
LT fuel% trim bank 1 is -8.59%
LT fuel% trim bank 2 is -11.72%
Fuel pressure stays at 58psi even after 6 minutes of idle
MAF at 6.8 g/sec
Cat temps are 568 degrees
Fuel/air ratio 14.63

Since the last update, I have replace the ground wires and the crankshaft

 

[JimTahoe]

UPDATE: #6 intake lift is stuck closed again. This was the original issue that caused me to do all the work. These are new lifters. Why would this keep sticking?

 

[j91z28d1]

where did the lifters come from? I've seen a few threads about having to do the job twice and it I seem to remember they didn't use oem gm or millings lifters.

but the vlom solenoids can be bad too, and it doesn't open and close them at the correct time and damage the lifters. there's a ton about it online. damage can happen from a few different sources.