Plugged Cat Converter?

Hey there, I'm chasing a fuel consumption problem and I'm wondering if a plugged cat converter could be a culprit and how do I test for this? I own a 2000 Blazer 4X4, 95K's, I've replaced plugs/wires, O2 sensers(3), fuel filter,
air filter, brakes/all around, cleaned MAF sensor, flushed tranny/filter, fuel inj
cleaners, new tires(same size) 235/70/15. No lights, no codes just crappy fuel economy 500km/60 liters or about 18-19 mpg all highway. What other issues can arise from a plugged or partially plugged cat?

Thats doesnt seem to bad. I get about 15 mpg on the highway, thats also with 31's and 3" lift

I average about that on mine, 18-20mpg on the highway. I think that sounds pretty good.

Yip, that is good.

Nothing to complain about there.

Which O2 sensors did you change?

If you want to help your ecomony, put a better flowing muffler on it.

The stock muffler is huge and really restrictive.

I've changed all O2 sensors(3). My economy was previously much better,
around 21-22mpg (highway). Does a fuel system flush restore some performance?

This may be dumb, but if you are running the Air Conditioner it may be hurting your MPG slightly.

Hey there, I'm chasing a fuel consumption problem and I'm wondering if a plugged cat converter could be a culprit and how do I test for this? I own a 2000 Blazer 4X4, 95K's, I've replaced plugs/wires, O2 sensers(3), fuel filter,
air filter, brakes/all around, cleaned MAF sensor, flushed tranny/filter, fuel inj
cleaners, new tires(same size) 235/70/15. No lights, no codes just crappy fuel economy 500km/60 liters or about 18-19 mpg all highway. What other issues can arise from a plugged or partially plugged cat?

A plugged cat will rob power long before mpg , but anyways to check it without removing pipe a pressure gage can be hooked to exhaust system before the convertor. I used an old spark plug with the gutsd removed and adapted to a heavy duty hose and can screw it into the O2 sensor hole and use the gage inside the cab. Just a couple pounds is normal when running full rpm and wot, I have seen systems with plugged cat peg a 60 pound gage and these are the ones you can also hear the sound.

I've changed all O2 sensors(3). My economy was previously much better,
around 21-22mpg (highway). Does a fuel system flush restore some performance?

You sound like you keep good tabs on your mpg, I agree 22 down to 19 is pretty drastic for no apparent reason. Mine gets 22-23 highway and 18 on city streets. The city mpg has come down 1 + mpg over the years. One thing I would do first is to verify the figure (you probably did already) :lol:

Check odometer calibration and gallons if possible, It may also just be a fluke and you happened to fill tank higher or made a mistake on figures also?

How many tanks did good on mpg and how many tanks did poor?

Did you change routes, speeds, drivers, ect.?

Also, did you recently change tires?

Add anything to the truck? Subwoofers and such? Hood or window deflectors?

For what it is worth, I just dumped the big bottle (there are two sizes) of Techron fuel system cleaner into a full tank of gas. This was recommended to me by the mechanics at the dealership. GM sells a similar product for $30 USD. I bought this at Autozone for $10 USD. I'm sure Wal-mart sells it too, Probably cheaper.

If you look real close at the GM bottle, somewhere on the bottle or on the label, there is a chevron symbol.

Anyway, I went from 235 miles per tank (Approx. 20 gal tank) to 330 miles per tank. IN JUST ONE TANK FULL.

It is worth the $10 and won't hurt a thing. But be sure to use the Techron and look for the Chevron symbol.