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1990 GMC Sierra 1500 (5spd) lifters knocking. Engine lopes, when excelerated. Rpl PVC valve, changed oil, rpl spark plugs,new exhaust line. Oil pressure gauge low.Purchased with quite a bit of oil sludge. I've changed the oil several times since purchase at 115k, now at130k.Could this be a bad or clogged oil pump? Suggestions?
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There is,If you do the lifter you could be after something else,The noise sounds like a collapsed lifter,A collapse lifter can cause a misfire,The 2003 GMC sierra or I should say the 4.8 engines suffer from a cut O-ring between the oil pump screen and the oil pump causing oil areation,resulting in lifter noise,The noise will be present a cold start and then diminish at warm up.
You may have a bad oil sending unit this is located under the hood near the oil filter two wires are connected to it. i would change this and see if your problem persists, if so you could have an oil pump you wont hear anything until its too late. 20 psi is all you need to keep it alive. good luck
The pcv is on the drivers side valve cover. It's an orifice type system and only needs to be checked for blockage which usually don't happen. If you can see through it don't replace it.
In some oil filters they have anti drain back valves in them, what keeps oil in the filter when sitting for a long time. this helps get oil to ur top end quicker. If not i takes longer to get oil to ur rocker arms so you might hear a knocking or ticking for a while. Try when u do ur next oil change to get a filter it a anti drain back valve and that should help make that noise go away quicker.
Try a cup of tranny fluid, Dextron, or whatever, in the crankcase. Or there are lots of lifter products at your local part store. I would certainly try that first. I assume your oil has been changed recently, and the level is good. You don't have to pull the heads, but you do have to remove the intake, and valve covers.
the knock sensors are located below the intake plenum,or,upper intake manifold as some call it, they screw into the lower intake, the front one is sensor 1, the rear is sensor 2. it is wise to change both if you have some miles.since you are going to be buying a gasket set to do this job.the sensors are cheaper than the gaskets.
I'd consider some fresh, clean oil & filter change first of all, if it hasn't been done . drive it for a while providing it isn't too bad, & see if it goes away, if not get back to us.
CHECK THE OIL PUMP SUMP TUBE O-RING. THEY COLLAPSE CAUSING THE OIL PUMP TO PULL AIR INSTEAD OF OIL. TO VERIFY OVER FILL ENGINE OIL AND CHECK ENGINE OIL PRESSURE. THIS IS A COMMON PROBLEM ON ALL NEWER GM V-8 ENGINES : 4.8 5.3 5.7 6.0
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