When I start my car after it has warmed up I get a puff of BLACK smoke not to be confused with blue smoke from bad valve seals. This only happens when the car is warm and I start the car right after I have turned it off. If I wait about 10 min the smoke does not appear. Someone told me that this might be due to my hollowed out cat courtesy of the previous owner and I was wondering if any one else has experienced this issue. The only other thing I can think of is that the car only has a cold start function where a lot of gas is injected to aid the starting of the car when cold. Any other ideas would be great help. Thanks everyone. By the way this is on an 88 firebird 305 TBI. Thanks again.

 

The only time I've seen black smoke coming out, was when the engine was not getting enough air.. could there be some major air restriction when your engine is cold during startup? Also another thing I'd check is if your cat has a pipe running through it or if the thing is right hollow... If thats the case I'd put a straight pipe thorugh it and see if it helps.

 

My truck did that with leaky injectors dumping remaining fuel pressure into the intake when I turned off the engine. I had my wife turn the ignition on while I looked at the injectors and sure enough one of them squirted gas consistantly while the fuel pump was priming system.

 

I have put on a rebuilt TB with new electronics and injectors and this did not help. This puff of black smoke only happens when the car is warmed up and only lasts for a second and I thought when the cat was hot it would kind of grab the unburned fuel and burn it off. But since I dont have a cat the unburned fuel just blows out the tail pipes. This could present problems when my area starts emmission testing because I could be failed for visible smoke. Thanks for the replies so far.