rodknock, how can you tell

[RPSil13]

so im having an issue w/ my supra, after driving the car for a bit (10-15 min) at operating temp and i come to a stop sign, my idle drops to about 700 and i can hear a sound coming from the engine, it sounds like theres a marble in the oilpan, but i lightly put my foot on the gass and bring the rpms to 1000 the noise goes completely away, i thought it could have something to do w/ the timing and the timing is at 15 BTDC, iirc its supposed to be at 10-12BTDC, does this sound like its developing rodknock, is there a way to check/test for rodknock

thanks
any help would be appreciated.

 

[87M-GTE]

Use one of those stethescopes, listen to the side of the block while it is running (on a lift or something to that effect..) You should be able to pinpoint the location of the noise by doing this.

 

[GrimJack]

When you can hear the noise, simply pull the plug wires one at a time.

If one of the wires makes the noise go away, that rod's bearings are toast.

 

[RPSil13]

When you can hear the noise, simply pull the plug wires one at a time.

If one of the wires makes the noise go away, that rod's bearings are toast.

i will try this method, thanks,