Random misfire

2009 CHEVROLET SILVERADO
130,000 MILES • 5.3L • V8 • 4WD • AUTOMATIC
Avatar
FLAITZ
  • MEMBER
  • 3 POSTS
Had p0300 code, I believe is random misfire, found out I had collapsed lifter on cylinder 1 and 7 so I put all new lifters in it and replaced the VLOM (Valve Lifter Oil Manifold) now cylinder 1 and 7 shut off as soon as the truck starts and continue to misfire. Took it to the dealer and all they want to do is tear the engine apart.any ideas will help.
Aug 23, 2020 at 11:38 AM
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.
Advertisement
Avatar
JACOBANDNICKOLAS
  • AUTOMOTIVE REPAIR CONTRIBUTOR
  • 110,190 POSTS
Hi,

Are you presently getting codes P3401 and P3449? Those are the deactivation codes for cylinders 1 and 7. I need to know if that is the case. If it is, there is a wiring issue. It could be a short to power, open circuit, or a short to ground.


If you have a scan tool that can operate components, with the engine running, command the affected cylinder deactivation solenoid "on" and "off", with a scan tool, while observing the following cylinder deactivation control circuit status parameters. From that you will know if it is an electrical issue.

Let me know.
Joe
May 5, 2021 at 1:43 PM
Advertisement
Avatar
KASEKENNY
  • AUTOMOTIVE REPAIR CONTRIBUTOR
  • 18,907 POSTS
Can you give a little more detail about the cylinder shutting down as soon as you start the engine? Do you mean that you have misfires on 1 and 7 as soon as it starts? Does the engine run rough?

Just to make sure, did you install the active fuel management lifters in these cylinders? If not, this is most likely the issue.

Take a look at the attachment where it says 1,4,6, and 7 are your management cylinders and require different lifters.

Let's start with this and go from there. Thanks
Image (Click to enlarge)
Attached Media
May 5, 2021 at 1:43 PM
Avatar
FLAITZ
  • MEMBER
  • 3 POSTS
I am only getting p0300 code, with the valve cover off. all the rockers move when I crank it over but when it starts 1 and 7 stop moving like it was turned off.
May 5, 2021 at 1:43 PM
Avatar
FLAITZ
  • MEMBER
  • 3 POSTS
Yes, I replaced 1-4-6-7 AFM lifters.
May 5, 2021 at 1:43 PM
Avatar
KASEKENNY
  • AUTOMOTIVE REPAIR CONTRIBUTOR
  • 18,907 POSTS
Interesting. Are you sure that they both were installed with the notch correctly placed as shown below? If not, then it sounds like they are getting shut down like you are in 4 cylinder mode. That is the purpose of this system that it closes these valves by having the lifter stop moving the valve and it traps air in the cylinder so that when the piston comes up it compresses air which acts like a cushion. In other words it is an inactive cylinder but the air cushion helps bounce the piston back down.

The fact that the valves are not operating when the engine starts points to this as the issue.

If we are sure they are installed correctly then we need to look at the control side but that is unlikely as it is only 2 of the 4 cylinders which points to an issue at the cylinder like the lifter.
Image (Click to enlarge)
Attached Media
May 5, 2021 at 1:43 PM