Director

Danny Instructor Quebec Posted   Latest   Edited  
Updated
Driveability
2009 Chevrolet Avalanche 5.3L (LC9) 6-spd (6L80)
P0304 — Cylinder 4 Misfire Detected

It started with stuck lifters. I replaced all lifters on the bank sent the head to rebuild. replaced the control board for the cylinder control system as one actuater was defective. found one coil coroeded replaced coil wires plugs and injector #4 at the request of the customer. Reassembled the engine. Still p0403. rechecked compreshion still 0 psi. opened the valve cover and ran engine rockers are not moving. Rotated engine by hand rockers are working with engine not running. Did a contunity test on the wireing between PCM and controler all tests good hooked up my modus to the wires all but one gives a good signal one is 1/2 the voltage of the others. Replaced the PCM and had a reflash done still P0304

-1
Jonathan Educator
California
Jonathan Default
 

Danny; Good afternoon Sir, I hope all is well. If the rockers don't move when cranking the engine using the Starter Motor but they do move when cranking the engine by Hand, then the problem is Oil Pressure. It sounds like you have Oil Pressure Bypassing the Solenoid and Unlocking the Lifters. Try Unplugging the Oil Control Solenoid for that set of Lifters and see if Compression Returns. If so…

0
Default Ð Awarded
Danny Instructor
Quebec
Danny Default
 

I replaced it with a new one twice no change tank you

0
Default Ð Awarded
Victor Owner/Technician
Florida
Victor Default
 

Place two tablespoons of engine oil(20/50) into number 4 cylinder and see what happens.

0
Default Ð Awarded
Danny Instructor
Quebec
Danny Default
 

Tryed two squirts and did wet test rocker arms are not moving with engine running

0
Default Ð Awarded
Danny Instructor
Quebec
Danny Update
   

I am starting to wonder if the oil passage in the engine block could be blocked. Also gave new lifters 8 hour soak in new oil before instalation

0
Update Ð Awarded
Jonathan Educator
California
Jonathan Default
 

Danny; Did you try unplugging the Oil Control Solenoid for Cylinder #4. With the Oil Control solenoid Unplugged did the Rocker Arms Move, Did the cylinder have compression.

0
Default Ð Awarded
Tyler Technician
Kansas
Tyler Default
 

Hey Danny! You're sure you have the replacement lifters clocked in their trays correctly? They're supposed to go in one way, but it's possible to install them 180 degrees out.

0
Default Ð Awarded
Stephen Technician
Tennessee
Stephen Default
 

Seems to me, that if neither rocker is working,then both valves are closed. I would expect at least some compression. And if the rockers are working during cranking it should have normal compression. Maybe there are 2 issues.

-1
Default Ð Awarded
Disagree
Victor Owner/Technician
Florida
Victor Default
 

It makes one wonder if there is any piston movement in the cylinders.

0
Default Ð Awarded
Scott Technician
California
Scott Default
 

have you checked camshaft lobes to verify they are not flat? have seen DOD lifters completely wipe out the lobes.

0
Default Ð Awarded