what have I done? 2007 NBS silverado 6 L Vmax

[toolsinbox]

Ok my new code reader spit out code Po307 which translates to a misfire on cylinder #7

 

can someone tell me which is cylinder # 7? is it the same a sm blk 350?

[txab]

Yes, same config as a 350. Drivers side bank. Last cylinder against firewall

 

Check plug wire and plug. Swap #7 coil with another to see if misfire follows it. Check for intake vacuum leak

[toolsinbox]

Thanks TXAB.

 

Pulled # 7 plug and its fouled switched it with # 1 plug and no change. Then switched plug wire and same code. I have been clearing the code every time by the way. So far its not the plug or plug wire. Took off K&N air filter and it is dirty as hell but started the truck without filter on and still running rough but seemed to have better response. I didn't wait for the check engine light to come on as the filter is not causing it. Next is the coil I guess.

[toolsinbox]

Ok switched coils # 1 with # 7 and same condition and p0307 code again. Now I will look for vacuum leaks. Not sure where as the only hose I can see is the brake booster. I guess I will continue digging.

[toolsinbox]

I need some pointers on checking on intake leaks. much thanks.

[toolsinbox]

I sprayed carb cleaner all over the place and no change in idle. I cleaned the throttle body it needed it. I cant find any intake leak by the carb cleaner spray method. The same code keeps kicking and it just wont idle. Take it for a spin and the shifting starts acting up and power goes away. I guess its time for a compression on the # 7. Any other suggestions are greatly appreciated.

[Blue Chevy Truck 20657]

Don't ignore changing the fuel filter. Chevy trucks are very sensitive to dirty fuel filters, and the condition won't always show-up in a trouble code. The good news is you can fix it yourself in less than an hour.

[toolsinbox]

Where is the fuel filter on the truck? Is it on the frame rail? I am doing a lot of reading right now on all this and it seems that the fuel pressure is a key factor. I am looking for a utube vid on how to test that. Where you hook up a gage etc.

[Chris]

No serviceable fuel filter on your truck. There hasnt been one since 2003. As for testing pressure, I think there is a port on one of the fuel rails

[toolsinbox]

wow what fuel gage fits that port. where do I get one?

[Chris]

Your local parts house should have a gauge for that port

[toolsinbox]

I just talked to my bud who is a snapon dealer he told me he is out of stock but they are $ 500.00. I asked him if the off brands fit and he said they come with several common fittings. I will try and buy one tomorrow. He is on the phone with some of his contacts to see what they think of my truck issues.

[Chris]

http://www.autozone.com/autozone/accessories/Tools-Garage-and-Equipment/Fuel-Pressure-Tester/_/N-25eb

[toolsinbox]

I found a local test kit here for 60 buks but my Snapon pal is texting his client- a GM tech who is camping and he is strongly indicating an internal leak on the intake. he is saying that spraying carb clean wont show anything as it would be internal leakage. He says that it is always an intake leak 99.9 % of the time based on what I am describing. he goes on to say that the leak will be right near the #7 injector. I hope there is a video of removing one of these intakes on utube? I think they are made of plastic. no over torking action lolol

[Snow White]

at first i agreed, sounded like an intake manifold leak until i read that it No.7 miss firing....

 

I wouldn't spend tooooooo much time with the intake gasket issue and here's the best way to tell without tearing it apart.

 

if the only time you have misfiring on the cylinder is when the truck is cold and it's cold outside ok, likely an intake gasket because when it's warm and the truck is warm the leaks typically go away, but they run like shit the colder it is. now if you have a big chunk of gasket missing then ok.

 

i think you should do a cylinder compression test because, my hunch is, you've got a broken lifter on that deactivating cylinder and it's not opening the intake valve or the exhaust valve.

 

also, i see that is a max tow package so you're 6.0L has the deactivating cylinders AND variable valve timing, if i recall... somebody confirm?

 

http://www.gm-trucks.com/forums/topic/150319-dod-lifter-replacement-on-07-60l-l76/