My Vr commodore has just undergone a rebuild and the number 3 piston is back firing. the plugs and leads are knew and i am stumped. the engine is struggling however if i remove the spark lead or injector from #3 piston the backfireing and shudder goes away. i thought the coil pack was dead however it still sparks at number 3.
This may be due to a brunt valve or misadjusted valve, the back firing is due to the intake valve being open while its firing in that cylinder.
Make sure all wires to cylinders are correct and not crossed.
My first thing i would look at is the firing order, may be a crossed wire, even if it starts and runs you may still have a crossed wire, then if firing order is correct then i would move to checking the adustment on the valves for that cylinder,
Make sure rocker arms arm tightened correctly and push rods are in correct locations. i know that some engines like the 3.1 have diffrent size push rods for the exhaust and intake, remove the valve cover and see if that valve is closed, or try a compression test on that cylinder and if it is low then you have a bad valve or it is not adjusted correctly and last the timing chain is not aligned correctly.
Testimonial: "I wish i read this before i went hell for leather would have saved me 1hr diagnosis (the exhaust valve on number 3 piston which was the dead piston had worked its way loose on the rocker arm and so was not opening as a result the car sounded teriable so now i have put a soft lock tight on the rocker screws to secure in plcace. Thankyou"
SOURCE: Misfire on cylinders 2 & 3
Check that distributer cap is on straight, some times go on misaligned. Change if you have to. Also check timing, could be out a few thou.
SOURCE: my VS COMMODORE needs attention when i accellerate
The timing of the engine has gone haywire. Try to align the cam shaft notches of corresponding pulley and set the tensional bolt back to same position, before removal of the belt, The alignment has to be perfect.Disruption of timing of firing other the engine. Higher the rev, the faulty the engine will not be able to take up the load....sodeep
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Its a VR not volts wagon. thanks for the segestion with TDC but iv already tried btw its a push rod hydrolic lifter v6 3.8l engine. its back firing into the intake manafold and the back fire goes away only when i disconect piston three spark or injector
I wish i read this before i went hell for leather would have saved me 1hr diagnosis (the exhaust valve on number 3 piston which was the dead piston had worked its way loose on the rocker arm and so was not opening as a result the car sounded teriable so now i have put a soft lock tight on the rocker screws to secure in plcace.
Thankyou
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