there is some sort of knocking coming from my sohc coupe...it sounds like its coming from the motor but only does it when the car rev to 3000 rpm...i used sheap oil in it just to flush out the old stuff but could it be from the type of oil?

 

it could be a myriad of things,

but based on what you said, itsounds like rod knock.


need more details to make any judgement

 

yea i think so but the car had a new motor put in it 20,000 miles ago thats why i dont get it...how could i find out if it is a rod knock for sure?

 

run the motor and remove one plug wire @ a time.If the knocking sounds goes quieter, then thats the offending cylinder.

 

thanks bro ill try it 2morrow and let you know for sure

 

Rod knocks have a relatively deep, hollow tone to them. Is it like that or is it more of a clacking metallic sound?

You could always put the car on jackstands and have a buddy rev the engine while you listen to the oil pan. If it's a rod knock, you'll know.

 

yea it starts at around 3,000 rmp and sounds kinda like a rod knock,i pulled each spark plug wire otu one at a time and still the same thing a went under the car and started it and it does make that noise around there..it really weird like i said ...in the hayens manual its says that it could be from not the right octane or old gas....when i boughtthe car it had a 3/4 a tank full but has been sittin for over a year because of a bad tranny.so i bought it and put a tranny in it and i never heard the sound then i let it sit for a month while i did body work on it and changed the oil with the cheapest oil in it from advance auto then i noticed the noise...