I have my brothers 93 blazer at my house so I can swap out the motor for him as he does not have alot of money and I like to help him out when I can. Here is the thing when you first fire it up cold it sounds and runs great and has about 45psi of oil. Once warmed up the oil psi drops to about 5-10 at idle and 30+ when on the freeway. Also when warmed up you can hear what sounds like a little rod knock. when the rpm's come up it goes away but is right back again when at idle or just above. Most of the time it is not very loud but will increase from time to time.

A friend stoped by and had the same vehical from new to about 120K miles and said his did a simular thing at about 80K and he was told it was a common problem in the TBI's called piston slap :confused: Has anyone heard or had this problem? He was told not to worry about it and it never became a problem. I would like to same my brother money if I can but I don't want this to brake down on him some where eather.

What do you think should I put a new oil pump in and just have him run it? Or are their any ideas out their I should look in to first? Any help would be great as like I said he does not have much money but he is willing to do what is needed even if it means having to charge (He just paid off all he cards ) it to get it fixed. I am doing all labor free for him and I can do anything needed but it is going to cut into the buggy time and my Atlass from Jess should be here any day now. Any help would be greatly appreciated :D

Kevin
Dixon Ca.

Send an oil sample out and get an oil analysis done. That will tell you if the engine has had an internal failure. Also, you wont get piston slap when the engine is hot. only when the engine is cold, due to the piston's "slapping" the cylinder bores because they are cold, and small. What oil are you running? Try stepping up to a thicker weight oil than the factory recommended 5W-30. I run 15w-50 Mobil 1 Synthetic in my 89 K5, and I gained about 8 PSI at idle hot, and 15 PSI at freeway speed hot. Pretty good improvement if you ask me.

I would pull the pan and check out the bottom end. Maybe even change the pump while the pan is off. I had a tick/knock show up in my 1989 TBI 350 that is in my Jeep. (Ran perfect for the last 6-8 years before) It ran for about 8 hours with the new noise and then punched a nice hole in the block. It would have cost much less if I rebuilt and did not need a new block. It looks like a nut backed off on one of the rods, but who really knows- see pic. I never modified or touched any of the bottom end - kinda weird.