5.3 misfire after wot lifter collapsed

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Racer71
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5.3 misfire after wot lifter collapsed

Post by Racer71 »

I have a 10 5.3 Sierra came in owner thought lifter was stuck in afm/4 cyl mode. Says it happened after passing a car. Lifter would move rocker while cranking over but once started it no longer moved. Swapped lifters with melling units, disabled afm with hp tuners as I’ve done to over 350 trucks now. Two weeks later he returns says it did once again after kickdown. Same cylinder same lifter no longer moving rocker. I pulled the head again replaced the affected lifter. After driving 30 mins or so decided to step into it same thing. It never a pumps back up or comes out of it. What gives? Typically when they come with a lifter stuck in afm mode rocker arm is loose. Usually tapping on it through the oil passage gets it unstuck, these however haven’t been stuck compressed. I would have thought that the lifter would come back after cooling off etc but doesn’t. I don’t think my dial bore gauge will measure the lifterbore. I’ve thought of removing and plugging the secondary oil pressure relief valve near the filter. I usually plug them if I have the pan off since were deleting the afm anyway.
dannobee
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Re: 5.3 misfire after wot lifter collapsed

Post by dannobee »

VLOM filter screen plugged? Is the engine oil pressure low?

Do you have access to SI2000? Doc ID 4455388 (PIP4568S) goes over the correct diagnosis and repair.
Racer71
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Re: 5.3 misfire after wot lifter collapsed

Post by Racer71 »

Replaced vlom after second failure with one from a truck that was fine, but owner wanted cam swapped. Oil pressure is normal for these trucks. Yes I have a gm dealer login for service info reflashing etc. just so curious that it’s been same lifter three times now
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