I have a 94 s10 blazer 4x4 and just recently black soot has been coming from the tail pipe. Also, I have noticed that the engine is idling rough when I am stopped at a light and the catalytic converter is smelling really bad. What could be my problem?

 

Possibly an internal fuel leak that is causing the rough idle and over fueling while you are driving down the road. This would also make the exhaust smell worse. I would start with a fuel pressure test, specifically watching the leak down rate. You should only see around a 2-3PSI drop once you turn the key off and it should not drop from there. If it does, that indicates a leak somewhere in the fuel system. The CPI motors are notorious for having internal fuel leaks.

It is also possible that you catalytic converter is at fault or has become faulty due to the aforementioned problem (fuel leak). Do you hear any rattling while you are driving?

Again, I would start with a fuel pressure test and work from there.

 

Yeah the tail pipe seems to be rattling while sitting at a light but as far as driving down the road i don't hear a rattle.

 

This could be the catalyst in the catalytic converter rattling around. If that is the case, then it sounds like your cat is to blame and things will only get worse.

 

unbolt the cat and start it up

 

This is a classic Blazer problem. Please, someone correct me if I'm wrong, but doesn't the dumping of the fuel lead to the clogging of the EGR valve, and then the loss of braking power? I believe that's how a mechanic explained it to me years ago. Be prepared to stand on those brakes, Big E.

 

The loss of brake power is a new one...

 

also u could check ur spark plugs too cuz if u have a fuel leak inside the plenum u would be able to see by this.