i have a 94 1.8 ls and after my car sits for a while when you start it it will rattle for a few seconds then stops i have change the oil and the motor has just been rebuilt any ideas what it could be..im thinking oil pump

 

more info is needed...how many miles are on the rebuild??????? what does the rattle sound like???? any check engine lights?????

 

is it a loud knockin when you start up the car and goes away after it warms up? If so you may need a valve adjustment if it hasn't been done yet.

 

it has about 1500 miles on the rebuild. and yes its a loud rattle and only lasts a few seconds then goes away..thanks for the info guys

 

I don't think the internet can help you identify the rattle until you can locate where it's coming from. If it's coming from inside the motor itself, yes you probably need a valve adjustment. If it's coming from under the car, it's probably your heat shield. If it's coming from inside your car, who knows?

It would help greatly if you could say where it's coming from and what it sounds like (metallic sounding, knocking, etc..)

 

It's either a rod knocking or a piston slapping around briefly before the oil pressure light goes out.

MikeSarr and I have had issues with it, and my friend just had his first bout of it tonight on his unopened motor (~100k miles). Mike replaced his oil pump with a new one, but I reused my old one with 75k miles on it.

I'll know more about it when I overhaul both of the motors later on this year.