I hope someone can help me out here. ok my engine makes this rattling noise when at idle or very slow speeds (parking lot, etc) and I am trying to figure out where it is coming from. i have posted about this problem before and had gotten some helpful info but i still can't figure out what is causing it. I have already completely checked the exhaust system (pipes, heat shields, clamps, hangers) and its not them. The sound is coming from the underside of the front of the engine right near the crank pully. So I'm going to take my last stab at this, I was wondering if the cause of the noise could be the timing chain. I have read that it is good to change it after 100,000 miles, my car has 144,000 miles. Could anyone tell me if this sounds correct? any info would be great, thanks.

and in case you need to know my car is a 1990 formula 305 tbi

 

It could very well be the chain with that many miles. Take off the distributor cap, turn the engine over by hand, (using a breaker bar on the nut at the crankshaft)watch how much the rotor turns in comparison to how much you turn the crank. I cant remeber how many degree's of slop is ok, but if its probaly obvious if you turn it alot before the rotor turns. Anyway I have done this in the past to check with great sucess.

 

thanks I'll have to try that

 

Check to see if your harmonic balancer is worn. The rubber insulator between the outer and inner rings wears over time causing the outer ring to walk. If it walks into the timing chain cover it gets really noisy.

 

I have this exact same problem too, same car, same engine, same year.

Matt, did you ever fix your problem or find out for sure what is causing the rattle?