Brothers

Hummer H2 2006 - 50k miles on new engine

The entire story on this engine light coming on and a Code P0300 on my OBD is something that won’t go away. Two mechanics, all plugs, wires, ignition coils, etc changed out. The valve covers removed for inspection and so on.

Yet when I drive for a couple of hours and things get hot, including the weather, I stop and when I restart the engine it throws the code. No specific cylinder code with it. No feeling of anything wrong, everything works fine. My OBD reader is ok but does do what the pro readers do, but I took it to two shops.

i make this same trip each week and when it’s hot out it comes up. Today was raining and in the low 90’s and the code did not appear.

I see its a common problem with Hummers this age. The shops I took the truck to are well respected and the second shop did the swap on my engine a few years ago and they had a team of guys checking it over. They couldn’t find a thing.

Anyone have any similar problems?

Ted

 

 

they need to check your fuel pressure when you are having the issue. your fuel pump or fuel regulator might be failing.

 

I drive to a area of Texas where there is not much in the way of Mechanics and when I get back it’s late.

One thought is to upgrade my OBD tester. I use OBDLINK SX. It’s been good for what I need it for but maybe I can pinpoint the problem with a better tester? Any suggestions on how I could test this myself?

Thanks

Ted

 

you would need to attach a fuel pressure gauge to the fuel rail. if it dips lower then 55 Psi then it will starve for fuel.

 

That is not going to show you the carbon deposits on your valves.
Perform an induction cleaning.(I posted a cheap kit above)
Btw, only use top tier gas!

 

Has it done this since the engine change out or did it just start?

Neal

 

When it does it what range are the LTFT in?

The OBDLINK should monitor the fuel trims.