cyl 3 misfire, need help
05-26-2009, 02:18 AM
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cyl 3 misfire, need help I have a 98 z28. It has crane 1.7 gold roller rockers with hardened pushrods, dual valve springs with a g5x2 cam. I was driving the car, not even getting on it, and then all of a sudden I feel a lot of vibration around 2500 rpm and up. There is ticking coming from the driver side head/valvetrain. Ive checked to make sure the injectors are working, and it all spark plugs get spark. Ive taken off the valve cover and nothing looks broken or out of the ordinary. Then I drove the car down the street and the ticking got louder, and cel came on. I ran the scanner which said cyl 3 misfire detected. Im not sure which one cyl 3 is, but i think its the driver side 2nd cyl behind the power steering pump. I am going to do a compression check to make sure the valves are sealing. but other than that, what else can i check to see whats causing the misfire.
05-26-2009, 07:55 AM
#2
Go back and verify 22 lbs/ft torque on all your rockers, not just #3.
Do it the proper way, bringing each cylinder to TDC firing position. Both valves completely closed, cam lobes on their base circle and not on the ramps.
With big cams and stiff springs, I've seen guys fail to get some of their rockers actually torqued onto the pedestal even though their torque wrench clicked at 22 ft/lb.
This happens because the lifter was way up on the cam lobe, the new springs were super-stiff, and 22# of torque just wasn't enough to overcome either the spring or the pumped lifter.
You end up with loose, noisy rockers and the bolt eventually either strips the threads or otherwise loosens.
Do it the proper way, bringing each cylinder to TDC firing position. Both valves completely closed, cam lobes on their base circle and not on the ramps.
With big cams and stiff springs, I've seen guys fail to get some of their rockers actually torqued onto the pedestal even though their torque wrench clicked at 22 ft/lb.
This happens because the lifter was way up on the cam lobe, the new springs were super-stiff, and 22# of torque just wasn't enough to overcome either the spring or the pumped lifter.
You end up with loose, noisy rockers and the bolt eventually either strips the threads or otherwise loosens.
05-26-2009, 09:13 PM
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Go back and verify 22 lbs/ft torque on all your rockers, not just #3.
Do it the proper way, bringing each cylinder to TDC firing position. Both valves completely closed, cam lobes on their base circle and not on the ramps.
With big cams and stiff springs, I've seen guys fail to get some of their rockers actually torqued onto the pedestal even though their torque wrench clicked at 22 ft/lb.
This happens because the lifter was way up on the cam lobe, the new springs were super-stiff, and 22# of torque just wasn't enough to overcome either the spring or the pumped lifter.
You end up with loose, noisy rockers and the bolt eventually either strips the threads or otherwise loosens.
Do it the proper way, bringing each cylinder to TDC firing position. Both valves completely closed, cam lobes on their base circle and not on the ramps.
With big cams and stiff springs, I've seen guys fail to get some of their rockers actually torqued onto the pedestal even though their torque wrench clicked at 22 ft/lb.
This happens because the lifter was way up on the cam lobe, the new springs were super-stiff, and 22# of torque just wasn't enough to overcome either the spring or the pumped lifter.
You end up with loose, noisy rockers and the bolt eventually either strips the threads or otherwise loosens.
