1990 RS 305 TBI


I had 293 dollars in parking tickets that I finally paid in order to get my car registered this morning, I hadn't driven it in maybe two months, So I jumped it and it started, I drove it to the gas station to put air in the tires, and while I was doing that I heard a rattling when the idle would drop to like 500 or so (the idle surges because the AC is kept on to keep the fan running) so when the idle fluctuates low it starts rattling, but normally at around 800 you can't hear anything.

I could hear the noise from the bottom of the car as I was putting the air in, so I opened the hood ( i thought it was the rad fan hitting up against something) but I couldn't hear it nearly as well from the top of the motor, so I got under the car and you can hear it very clearly from the bottom of the motor.

There has never been an issue like this with my car before, I'm thinking either crank pulley or harmonic balancer, any ideas? It only occurs at low idle, 500 or under perhaps

Maybe the rubber around the harmonic balancer? Any suggestions are appreciated

 

Where under the motor? Near the front, or rear?
I've seen and heard broken/cracked flexplates do that, and if a flexplate bolt or two backs out and rattles between the torque converter and flexplate, the sound at idle is maddening......almost like a rod knocking.

 

for some odd reason i feel its something hitting the eexhaust or the heat shield on the cat

 

Near the front of the motor, Well it's a manual so there's no torque converter, but it would apply the same substituting the clutch. I'll listen to it near the flexplate next time, but I heard it from the front of the motor this morning

 

I get what you're saying about the "maddening sound" but it's not a low sort of knock you'd hear from a rod or anything, it's a rattle