Ive been trying to sort this out for awhile now, but can't seem to track it down.

I have a rattle noise coming from my tbi 305, and I cant figure out where it is coming from.


Ive seafoamed the engine, removed the smog pump (new belt and tensioner), and changed the alternator, none of which has helped.


It rattles between 800 - 1500 rpm, and will only do so after it has warmed up.

After it has warmed up and is at idle the rattle is intermittent, it will rattle for a few seconds, stop, then start again.

The rattle doesn't change with the RPM (doesn't get faster/slower), but it goes away after 1500 ~rpm.

 

Grab a length of heater hose. Hold one end of the hose to your ear and move the other end around the engine while it's rattling. This might narrow it down for you.

 

Try checking your exhaust components, like heat shields, clamps, hangers.

 

I had an almost identical problem... still do actually. If it sounds like a bad bearing type of rattling from the right side of the engine compartment its probably your powersteering pump. Mine is shot and rattles intermitantly just as yours does in the same rpm range as well. I searched for a little while but came to that conclusion.

 

mine is also a 305 tbi 1990

 

I have the same intermittent rattle and it's the RH donut gasket between the manifold and the y pipe. I can actually see that rattle back and forth when it makes the noise.

It sounds like a bag of loose change rubbing on a pulley but it's not.

 

PCV valve rattles with engine vacuum. Like was said earlier, use a length of hose to your ear and move around and listen.