91 s10 blazer problem

I have a 91 s10 blaver with a 4.3L TBI. and I am geting about 150-200 km on a tank of fuel and I was geting about 500-600 before now I am just wondering if any one might have some ideas that I could try to find this problem. I am geting alot of black soot from the tail pipe. I tryed a code reader and got a leen exaust code. So I am thinking the O2 might be bad but I have no idea how to test and it was replaced less then a year ago. I will post more info as I get more tests done.

Sounds like you are on the right track, but would check for vaccuum leaks. My 93 with CPI had a drop off (18-20mpg to 15+-) and I found a leaky hose was causing problems with that and my idle.

I have a 91 s10 blaver with a 4.3L TBI. and I am geting about 150-200 km on a tank of fuel and I was geting about 500-600 before now I am just wondering if any one might have some ideas that I could try to find this problem. I am geting alot of black soot from the tail pipe. I tryed a code reader and got a leen exaust code. So I am thinking the O2 might be bad but I have no idea how to test and it was replaced less then a year ago. I will post more info as I get more tests done.

I recently did a check on my 92 S-10 4 x 4 with the W 4.3 engine which is fI.

I went 255.3 miles, 3/4 of it was in the mountains on narrow gravel roads with much up and down steep mountains and around curves at speed of 29 to 35 MPH.

I used 12.188 gallons of gas, which made my MPG 21.1209.

Believe that is right good!

I rightly do not know how the TBI compares to the FI on MPG.

Jerry