2008 tahoe p0300...

[User_Name]

Thanks in advance for reading! 2008 tahoe 5.3 K1500 190k miles. The truck has no cats, just headers into a single dynaflow. So the 02 sensors are located about a foot or 2 from each other. It has been this way since I bought it a year ago.

Put gas in, drove back from lunch break, it was fine. Cranked it up to go home and it's running rough the whole way. P0300.

I checked the plugs, all plugs on driver side were pitch black. Passenger side were light brown, much better looking.

I replaced all plugs and wires. Still rough idle and random misfires on drivers side bank. Particularly number 3.

So I swapped number 3 and number 2 coils, erased codes. Getting P0300 and P0171 bank 1 lean. Still getting a lot of misfires only on drivers side bank though.

I am cleaning the MAF right now.

ST FTRM1 0.0
ST FTRM2 0.0

LT FTRM1 24.2
LT FTRM2 -25.0
MAF 0.80 LB/M
Fuel pressure 58 psi

Any ideas what I should try next?

 

[Dustin Jackson]

Could just be bad gas, I would drive that tank down and fill it with premium see if it helps

 

[User_Name]

Could just be bad gas, I would drive that tank down and fill it with premium see if it helps

I will do that right now. The truck has had a small miss at idle maybe once or twice a red-light. It has been going on for a couple months now, but it's never affected the performance. I am not certain which cylinder it was though.

 

[User_Name]

Could just be bad gas, I would drive that tank down and fill it with premium see if it helps

I got it down to the empty line and put half a tank in, gas is kind of pricey, but no change.

Cleaning the MAF also had no effect. Misfires are still all on drivers side bank.

 

[j91z28d1]

so drivers side is adding 25% fuel, passenger side is removing 25% fuel.

gotta admit, I've not see that one.

feels like swapping o2 sensors side to side and see if it switches might be a thing to try or if you have to money just replace both. they are considered a maintenance item.

 

[j91z28d1]

do you have any broken exhaust manifold bolts on the drivers side?

 

[Fless]

so drivers side is adding 25% fuel, passenger side is removing 25% fuel.

gotta admit, I've not see that one.

I've seen a case or two online -- although I don't recall exactly where -- where this happens due to over-fueling one bank will lead to the other bank trying to compensate. Hence the yin-yan activity.

 

[Joseph Garcia]

@OR VietVet

 

[User_Name]

do you have any broken exhaust manifold bolts on the drivers side?

No, I checked, all bolts are good, gasket looks good too.

 

[User_Name]

I will swap O2's this afternoon and check back in with yall. Thanks for all the input

so drivers side is adding 25% fuel, passenger side is removing 25% fuel.

gotta admit, I've not see that one.

feels like swapping o2 sensors side to side and see if it switches might be a thing to try or if you have to money just replace both. they are considered a maintenance item.

Npu