engine blow by

I have a 88 S15 and i every 3 weeks to a month i change my air filter and pcv breather because they are black already, i was told i coudl have worn out piston rings and oil is getting past and i was just wondering if anyone woudl have more information on why my air filter gets so dirty and so fast. thanks

Does it burn oil? How does the engine run, is it smooth, does it have good power, how are the intake gaskets, are they leaking, are you loosing any anifreeze, does the truck overheat?

Every engine has some amount of blow-by, thats what the PCV system is there for, to recycle these blow-by gases so to spesk. They get sucked up by the PCV system back into the intake and burnt off, thereby reducing the amount of pollution going out the exhaust. If the rings are starting to get worn, or are just dirty, they will allow more past, and enter the PCV system. In bad blow-by engines(worn or somthing mechanically wrong), you can take the oil cap off while the engie is running, and you can see gases exhausting. The air filter should not be affected by blow-by because the TBI system which yours has, doesn't matter 2.8 or 4.3L, the PCV intake pipe enters the throttle body after the air filter, so that will not affect your air filter. As for your PCV valve, yes that can be heavily affected by blow-by, and can be gummed up real bad too.

A little more about PCV systems...

The PCV, (positive crankcase ventilation) system uses manifold vacuum to ventilate the crankcase with fresh, filtered air. The efficiency of the PCV system is greatly reduced if the engine has a build up of sludge inside restricting the ventilation passages such as the oil return holes in the cylinder heads, and sludge in the overheads, and rocker arm covers. When those passages start to get restricted, the sludge builds up even more rapidly. When the PCV system becomes totally inoperative, blow by pressure in the crankcase will increase and start pushing out gaskets and seals creating oil leaks. Replace the gaskets without repairing the PCV system and they'll blow out again. Any time blow by pressure in the crankcase is excessive, it can and will find it's way out of the engine, even out of the breather filter, after all, that's the path with the least restriction.

While the engine is idleing, pull the PCV valve out of the rocker arm cover, put your thumb over the end of the valve, there should be a strong vacuum. If not, check the vacuum hose for a restriction, (you'll probably find oil sludge). Locate and repair the restriction and re-install the PCV valve back in the rocker arm cover. Go to the opposite rocker arm cover where you'll find another hose. Pull the hose out, put your thumb over the hole in the rocker arm cover, there should be a slight vacuum. If you see smoke coming out of the hole, either the oil return passages are restricted or the engine is creating more blow by than the PCV system can handle. If that's the case, worn, (or broken) piston rings and/or worn cylinder walls are the cause.

Several things can cause sludge to build up: PCV system not functioning properly, neglecting oil changes, engine operating temperature too cold, and coolant getting into the oil to name a few.

Hi i have a 2.5 inline four in my 88 S15 and i checked the oil and its still good its right up there and nto to long ago i changed my pcv valve because thats what i thto it was, but my air filter is still cloggin pretty quik. I have good power rite when i put a new air filter in the in aobtu a week ic an notice is is becomin a lil boggy. it had good power except when my filter is startin to get a lil dirty. my coolant is a lil low and i'm nto sure if its fr that tho, i have jsu under 200,000 kms on my truck. Everytime i change my air pilter i change the lil breather that is beside the air filter and goes into the valve cover, by the time i need to change my air filter this breather is also pretty black and when i tkae the lil holder out there is a lil bit of oil on the botom fr teh hose. thanks