smoking

[firebirdtrans]

i have a 91 240sx se and i just went over 190,000 miles and i just had the oil changed with 20-50 oil and everytime i start my ccar when its cold a hoel puff of smoke comes out the back and it only dose it on the start then after that its normal..before i bought the car abotu 10,000 miles ago the engine ECU was replaced, what could be cuase this smoking only on start up?

[ridebmx]

id say valve seals or rings...

[BlackFox]

if the smoke goes away then your cats are still working but sounds like you're burning some oil somehow or what ridebmx said, rings

[sykikchimp]

get a leak down test done to verify where your leaking.