97' 4.3 black smoke out of exhaust

I have 283K on this truck. When I have to give it some throttle I can see a cloud of Black smoke behind me. What causes this problem?

black smoke is usally from partially burned fuel could be lts of things , bad valve seats , improper fuel air mixture etc.

last i checked, it has oil blowby. various reasons might be to that. stick a napkin into the tail pipe and wipe the inside, then look at the paper. real sooty? you have your answer.
i'd say, it's engine overhaul, or you'll kill your cat for starters.

with unburnt fuel, you'll have gas smell outta the tailpipe. sometimes it ignites in the exhaust.

I have 283K on this truck. When I have to give it some throttle I can see a cloud of Black smoke behind me. What causes this problem?


check the vacuum line on the fuel regulator,,,not too sure with your vehicle but on the newer engines the regulator diaphram ruptures and then fuel is sucked into the engine causing a rich mixture which will destroy the cat converters...

check the vacuum line on the fuel regulator,,,not too sure with your vehicle but on the newer engines the regulator diaphram ruptures and then fuel is sucked into the engine causing a rich mixture which will destroy the cat converters...

think he got this one right, also the 4.3 fuel systems have a "spider" assembly, the regulator assembly and the fuel injectors are all one unit, the said above regualtor is also on this assembly, the upper intake has to come off to get to it, don't worry, a 15 minute job for someone who wrenches alot, cant see anymore than 45 for someone who doesn't. If any of the above is leaking you will run lean and have black smoke. Do you have any codes?
With 283k and the resultant carbon in the upper end, I am sure you would see "tracking" under a leak where the cool fuel from the leak has steam cleaned the inner parts of the intake.
Once again any codes? No reason to thorugh parts at it. Usually when the regulator leaks out it is hard to start if it sits for any length of time, because the fuel pump has to reprime the system, these things will not run unless they have adeqaute fuel pressure.

check the vacuum line on the fuel regulator,,,not too sure with your vehicle but on the newer engines the regulator diaphram ruptures and then fuel is sucked into the engine causing a rich mixture which will destroy the cat converters...

these have the same style, but they clamp onto the back of the regualtor assembly and leak into the intake plenum area instead of into the regulator line like the ones on the small block.
Years ago couldn't get em seperate, but any good parts house stocks the regulators by themselves. 95 engines were very bad about the plastic lines to the injectors splitting and leaking into the plenums, but by 97 they had that fixed. By that time usually the only problem they had was the regulators, unless someone put junk fuel in it and filled it up with dirt, BUT you would have lean problems then, not rich.