Can a fuel injection cleaning not following GM service bulletin cause p0304 code (misfiring#4)

Question

2007 Gmc yukon xl fuel injection system cleaned a couple of months ago, since then rough idle, check engine, stabilitrac & traction lights flashing with a rough idle. Dealership suggest new cam or new engine and a misfire #4 with a p0304 code. I jus read a service bulletin for the truck stating that only GM products should be used and it should be done according to their instructions. Could this possibly be a cause of my problem? Also there's a weird smell & gas hand fluctuations

Answer 1

P0304 Misfire number 4 cylinder

No, The Bulletin you reffer to is TSB # 05-00-89-072C. To begin with gasoline already has detergent into the fuel. Back then when fuel injection cleaning  was popular there where vehicles on the road with carburators. Today gas station now has to display a warning for carburator vehicles that todays gasoline can create leaks as todays gasoline is only intended for for fuel injection vehicles and the owner is held responsible and is advise to inspect for any leaks at the carburator that may occur. GM wants there only cleaing products again when car where carburated there was products that had Ketones and Methanol. That when added into the fuel tank interfered with the fuel tanks sending unit operation and causing it to malfunction. Yes this can  ruin the sending unit only if the sending unit was borderline to begin with.  Did fuel injection cleaning cause the misfire on your vehicle its possible that you would have this misfire condition regardless of the fuel injection cleaning. Why would a dealer recommend a new Cam?

 It is important you inspect the cylinder sparkplug that has the misfire and verify that , that cylinder has the misfire. Here this sparkplug show proof that a misfire on that cylinder is happening. What the sparkplug has is it is wet with fuel , and black which would represent low compression.

 The best way to verify low compression is a running compression. A running compression of 65 psi or lower would indicate a mechanical problem exist

 Running compression test would help identify the problem, here there is a small hairline crack between the intake valve and the exhuast valve. This is where running compression test is at its best a compression test would show this as a good compression test, and this problem would just go unnoticed

 Because your engine has individual coil and sparkplug wire  you can swap out the suspected coil and sparkplug wire with the sparkplug and install with another know working cylinder, if the misfire follow that cylinder ,  the misfire would be with the igntion coil or sparkplug wire and even the sparkplugs.