I have a 95 4.3 I was getting 400km to a tank. While driving the O2 sensor trouble code went off twice. I reset the code and it hasn't gone off since but my gas mileage has plummeted to around 200 km to a tank. Given that I'm in Canada and it's -25 to -30 it's warmed up for about 10 min prior to driving....but the millage is stupid low even for a Blazer... Thoughts????? O2 ?? Injectors???

 

My bet is a bad or lazy O2 sensor

 

I've been told that a bad O2 sensor can reduce mileage due to the computer not being able to optimize the A/F mixture. I've been getting an intermittent O2 error for a little while now. I just have not been in the mood to replace it but I will soon as my mileage has not been that bad.

 

Im in Canada also , Calgary Alberta and its been cold also ...my records show an average of 11 to 14 MPG since Oct , summer months are usually 14 to 16 MPG what are you getting ?. As far as o2 sensors being lazy and stuff .... I don't buy it , I changed all the o2 sensors in my 2 Astro vans at around 150,000 KM and in my latest jimmy at 200,000 KM and the fuel milage did not change one bit..... The sensors were tough to get out as well so I'm betting they were original. Maybe if a code shows a bad o2 and you can see it with a scanner....but other than that i'm not changing o2's to try and get something from it anymore.

 

That's only 125 miles per tank. For those of us in the USA that would be in the neighborhood of 8-9 mpg. Does sound quite low, but very difficult to diagnose without a capable scanner and 1995 is a bad year for that. If your vehicle has the OBD2 connector, you might get some basic scanner functions out of Car Gauge Pro or Torque or Dash Command and a Bluetooth OBD2 adapter. Do you aready have a scanner with capability to monitor basic SAE OBD2 functions? If so, are you able to look at O2 sensor voltages and fuel trims?


Read post #2 here: https://blazerforum.com/forum/2nd-ge...ers-95s-31043/

 

On a '95 , you need one of these!

 

Mine is about that bad as well, but I believe mine is from a busted fuel filler neck? The neck is fine, but it's got a piece missing (read: rusted off) at the top by the cap.Would that be enough to cause a decrease that bad too?