The first modern cylinder deactivation system produced was the 1981 Cadillac V8-6-4 and that was a big flop. It’s now a common feature of multiple vehicles and generally trouble free. But when you have a vehicle so equipped and it has intermittent performance you might blame that system. SureTrack community member pdmason1492 had a 2013 RAM 1500 truck with a MDS 5.7L engine with intermittent a misfire problem and thought that maybe the cylinder deactivation system might be involved. They posed the question to the community, and with the help of fellow community member Ericsautomotive and others, they were able to finally figure out what was wrong with it and repair the problem.
The following Community Fix summarizes the interaction between members of the community that led to the solution.
2013 RAM 1500 Laramie 5.7L
Misfire at high RPM acceleration, replaced camshaft.
Customer complains that check engine light comes on while accelerating.
Diagnostic Steps Performed/Parts Replaced
Took truck on test drive and found that it misfires on #5 cylinder after high RPM acceleration. Check engine light on and flashing. Stops misfiring at idle. Scan and verify #5 misfire and no other cylinder. Swap coils with #3 and no change, still misfire on #5 cyl. New plugs in #5 cyl. No change. Hook up injector noid light and fiber optic extension and found injector loses pulse and comes back at idle. Hook up injector noid light on #3 injector and under same conditions it loses pulse as well. Verify cylinders not part of the deactivation system. I believe the absence of injector pulse is a result of a issue internal of the mechanics of the engine. Maybe ECM cutting off injector to protect the cat converter. I do not believe the injector is at fault.
I understand the deactivation system cuts out #4, #6 (passenger bank) #1, #7 (drivers bank) by lifter oiling. I assume the ECM cuts the injectors off as well. Does the ECM have ability to cut other injectors not affected by deactivation system? Do you think the cam or lifters on #5 are causing the misfire at high RPMs and the injector loss is a byproduct of the ECM misfire detection? How do I know or test my theory? 6 months ago I had another of these same symptoms on a 2011 RAM Hemi but on #3 cylinder. I had even checked compression and replaced the ECM on that one and no change. That RAM still not fixed. I’m about to remove the valve cover to watch the rockers but what if?
Best Answer from Community Member Ericsautomotive
Pull valve cover and check the valve movement on #5 cylinder. These HEMIs are well known for camshaft and lifter issues! It always seems to show up first at higher RPM.
I pulled left valve cover and found #5 intake valve not opening very much at all. Cam worn. ECM must cut out injector during misfire to prevent catalytic converter meltdown.
Replaced camshaft and truck runs as it should and no longer misfires. Thank you for your suggestions. Will use you all in future.
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