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GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15133
Experience:  GM Grand Master Technician 2007. 14 years experience.
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2007 Chevy 2500 HD. 6.0L. I have a dead miss on cylinder 7.

Customer Question

2007 Chevy 2500 HD. 6.0L. I have a dead miss on cylinder 7. I have checked compression, spark, injector pulse, injector, spark plug, valves, and springs. Everything checks good. I even did a smoke test and can not find a leak. Any suggestions.
Submitted: 5 months ago.
Category: Chevy
Customer: replied 5 months ago.
Is this one to difficult to get a response?
Expert:  Ryan Schott replied 5 months ago.
Run it with the valve cover off and watch your rockers you could have flattened a cam lobe. Also swap the plug with another if the porcelain cracks too far in it can be difficult to see. If you don't find anything there do a leak down on that cylinder. Have you monitored fuel pressure to see that it doesn't bleed down when the key is off?
Customer: replied 5 months ago.
Have already taken the valve cover off and check the valves for proper movement. And fuel pressure is correct and no leak down.
Expert:  Ryan Schott replied 5 months ago.
have you pulled and cleaned inside your fuel rail, contaminants will build up on the ends and restrict fuel injectors, can you shoot me your vin
Expert:  Ryan Schott replied 5 months ago.
did you watch your valves while it was running or were you just tuning it by hand?
Customer: replied 5 months ago.
Activated the injector and verified fuel pressure drop.
Customer: replied 5 months ago.
Not running. Cranking
Customer: replied 5 months ago.
Will send vin tomorrow.
Customer: replied 5 months ago.
Expert:  Ryan Schott replied 5 months ago.
Does it have active fuel management?
Expert:  Ryan Schott replied 5 months ago.
Either way I would run it while monitoring that misfire and watch those rockers, you can rubber snub the coils over towards the booster for room. If nothing can be seen while the misfire is present and vehicle running, then its time to go back to step one, see if your spark is good and you can pull a large gap with it, if you can access an AFIT it will give a more accurate injector test, redo a leak down at a range of pressures, recheck compression and compare it to several other cylinders. If you go back through all of this and there is still no problem found you might need to try and measure the lift from your rockers or remove the head and visually inspect the cam and lifters.
Expert:  Ryan Schott replied 5 months ago.
I have seen a few with bad lifters and a slightly machined down cam because of it, you will get normal enough compression and it won't leak however the slightly insufficient valve opening will cause your miss.
Customer: replied 5 months ago.
Ok I will let you know my findings.
Customer: replied 5 months ago.
Turned out to have a faulty injector. Sprayed in a stream instead of a spray pattern.

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