1991 Firebird 305 TBI.....rattling noise on front of engine
 

I have this annoying rattling noise that is very similar to a bad idler pully. It gets worse as the engine runs longer. In fact I thought that's what it was so I replaced it. Nope rattling is still there. Thought it might be the smog pump replaced it. Nope rattling still there. I had already replaced AC compressor and alternator last year. What the heck is it? I thought it might be the water pump or power steering pump so I bought a mechanics stethascope and probed for the sound. It seems the loudest is at the timing chain cover but still not as obviously loud as the sound without the stethascope. It is also the loudest at idleing and seems to go away with acceleration.

Engine has 126,000 miles and runs great, no smoke, smooth idle, starts first try and has good power.

Re: 1991 Firebird 305 TBI.....rattling noice on front of engine
 

Probed it again thinking there is no way it can be the timimg chain. Timing and everything looks and runs good. I did probe the back side of the water pump instead of the front side and the squealing sound got much louder. It appears the pump is working but is this what I would experience if the bearings were shot?

Re: 1991 Firebird 305 TBI.....rattling noice on front of engine
 

Does it rattle when you remove the drive belt? If you haven't tried that yet, then do it.

Re: 1991 Firebird 305 TBI.....rattling noice on front of engine
 

It does rattle with the belt off.

Re: 1991 Firebird 305 TBI.....rattling noice on front of engine
 

I'd check for loose torque converter bolts or a cracked flywheel.

Re: 1991 Firebird 305 TBI.....rattling noice on front of engine
 

to check for a shot timing set.without disassembling the engine remove the distributor cap and rock the engine back and forth. the rotor should follow the movements of the crank with NO lag. if it don't ,well then a cloyes double roller timing set is in your future

Re: 1991 Firebird 305 TBI.....rattling noice on front of engine
 

My 305 TBI does the same thing, deleted the smog pump, new water pump, alt & P/S pump good, new tensioner, new A/C Compressor, replaced timing chain and gears with new. 109,000 on it. I am wondering if the cam is walking maybe or a bad lifter. Let me know if you figure out the problem it sounds just like mine.

Re: 1991 Firebird 305 TBI.....rattling noice on front of engine
 

Ok found the problem....the timimg chain was very loose, it was a wonder it hadn't fallen off or broke. Installed new chain and sprockets and then drove it 30 miles with no rattiling. I did find oil sludge in the timing cover, so now its time for a flush and use synthetic oil. I heard not to use solvents to flush but to use synthetic oil and a quart of Automatic Transmission Fluid and change oil more frequently until the oil comes out clean.

Re: 1991 Firebird 305 TBI.....rattling noise on front of engine
 

do NOT use auto trans fluid in your engine! unless you are looking for an excuse to build a new engine. I have seen the sad results of this misguided approach. not pretty. use a engine flush designed for this.afterwards change your oil and filter a minimum of 3 times and ,if I may suggest you not use synthetic oil in any engine with more than ,,say 50,000 miles it WILL start to leak.good luck and let us know how it went for you

Re: 1991 Firebird 305 TBI.....rattling noise on front of engine
 

There seems to be alot of opions on what and how to use certain things to help with engine sludge on an engine with over 100,000 miles. So what I did was use part synthetic and only half quart of ATF. We will see what happens.

Re: 1991 Firebird 305 TBI.....rattling noise on front of engine
 

spun crankshaft bearings is the usual end result.in almost every case that I have been hired to repair. but hey its your car

Re: 1991 Firebird 305 TBI.....rattling noise on front of engine
 

I could see running it VERY temporarily and then draining it out... but prolonged use of the extra detergent I can't see being a good thing.