Chevrolet Repair: 94 Chevy Blazer, chevy s10 blazer, oil pressure gauge

Question
I have a 4.3l chevy s10 blazer well i have had some issues with it as of late. Well ill break it down i was having a rough idel issue with the truck casuing vaccum lose which affects the power brakes well i had went all the way from a tune up to a new fuel pump well i had to it take into a shop they said replace the egr valve. well they did the work the truck worked pretty good for about a day. well then it went right back to a rough idle and i found that hunks of what looked like coal was sticking open the egr valve i guess it was the vapor canister causing that. well it ran fine till i noticed a coolant leak i noticed it was coming from the top near the valve cover so i assumed it was coming from the intake manifold i guess the gasket was blown. well i took it in they replaced it when i went up there they said there was some nasty gummie junk in the valve cover and it seem like they got it fixed well it ran great for about a dayi did notice that the oil pressure gauge was slowly going down and then my check guage came on. then all of sudden i got this knocking sound. it will only knock on accleratingit idles with no noise at all. i also notice that the oil gaguge almost shows no oil pressure. i checked the level of oil seems fine looks good. i started the truck busted lose the oil coolant line from the oil filter on top pushes oil out just fine. So i assume the truck is getting proper oil. well when i took the truck in for the egr issue or supposed issue they told me that my problem was carbon build up and that the only true way to fix that egr issue was to take the air intake apart and clean it out but they warned me that most times this can cause the motor to knock. well i am just not sure what to check or what to do. I used some marvel mystery oil to see maybe i may have a thick oil in there and all that and still has a knocking issue i am think something major like a lifter piston or maybe bearing but i am not sure.

Answer
Hi Dennis, Well I have heard the story before. Had a intake manifold gasket done and now it knocks!! When some poeple clean the intake gasket off the cylinder head surface they use a small grinder with a disc made by 3M and the stuff that comes off this 3M disc will take out engine bearings!! It makes the engine oil like a sanding fluid. The oil filter will not trap these small particals that come off the 3M disc, so into the oil system it goes. Sounds to me like you need a bearing job at the very least. As for the EGR, they make a gasket that has a screen on it to stop the carbon from getting into the valve. I use these on all the EGR valves I replace!!

Hope this helps you

Mark