Weird engine noise

[J-440]

Have a freshly built 440 with a FAST XFI setup. It's not tuned yet but runs really rich. It's been broken in awhile back but recently during a startup session I hear a consistent "pfft" sound coming right from under the throttle body. The car sputters, dies, then a little bit of white smoke escapes through the throttle bodies. It almost sounds like one of Jay Leno's steam cars as he's driving down the road. Like I said, the car runs rich and is not tuned and everything is brand new. Thanks again.

[benno505]

vacuum leak maybe?

[J-440]

Vacuum leak I can understand but would that cause a "poof" of white smoke to come out of the intake?

[benno505]

i dont know exactly what the white smoke is but when i was having running problems with my engine a while back and when the engine would die white steam/smoke would exit through the carb. i think it is just soemthing to do with the heat and unspent fuel in the intake.

i would just try and diagnose if you have a vacuum leak first then once it is running okay that smoke should not happen anymore

[sam 74]

best guess is a small backfire causeing the smoke, especially with a vac leak.

[TheJDMan]

I would be getting it tuned ASAP.