smokin' firebird?

Question

what would cause black smoke on startup? valve guides? it's just a quick puff of smoke, but it's enough to make the ground under the exuast pipes black. any help would be great thanks

91 firebird w/3.1 liter

Answer 1

black smoke = too much fuel. valve stem seals = blueish white smoke. Probably either a leaking injector or leaky pressure regulator. Have seen many fuel pressure regulators go bad. You can check by leaving the car running and remove the vac hose from the regulator. If the diapragm has ruptured there will be fuel coming out of the vac port. You may have to check this at various times, with engine running and without, first start after sitting overnight and after driving it a while. leaky injectors are a bit harder to diagnos. The best way is to remove the fuel rail and pressure up the fuel system. watch the end of the injectors to see if there is any fuel drops forming. may have to sit overnight, but if the pump doesn't hold good pressure then you'd have to keep priming the pump.

Answer 2

valve stem seals leaking is the first thing coming to mind. They can be changed without pulling the heads, but not without a few special tools and some knowledge. Good Luck

Answer 3

If it's black smoke, it is too rich on fuel meaning choke problems. If it's blue smoke that just means it's a GM . They all have bad valve seals

Answer 4

Fuel is leaking into the intake manifold while the engine is off.

You neglected to mention what year, so it's either your carburetor, TBI, or port injectors leaking.

Answer 5

black smoke is excess fuel, leaky injectors, fuel regulator or carb if its a carb. you are running too rich.