hey everyone i got a 02 blazer ZR2 when i first got my truck i was getting a little over 300 miles to a tank but never under 300 did a little offroading with it not much around me but any ways within about a month if not less i realized i went from 300+ to 200- miles to a tank and about10-13 mpg i drive from virginia to mass. or michigan alot and even on those long all highway the best i can get is about 15mpg if im going 65-70 and easy on the peddle witch is hard for me cause i normaly do 80 the hole way and got 18-20 mpg. i took off my maf and it had some mud stains inside. the wires are fine not broken but ive heard of them being bad and not poping codes befor but at $170 id like to try other possibilites first so any one got anything gas is to much to be gettin 200 miles on a 19 gal tank.
2002 blazer zr2 just under 60,000 miles
no codes poped
replaced: air filter, fuel filter,plugs,wires.4x4 is not engaged ive checked

 

I'd guess a problem with either the coolant temp sensor or the O2 sensor in the manifold (upstream).

If either one is sending incorrect readings, it can run much richer.

You want to see what these sensors are telling the PCM. If the CTS is saying it's -20 degrees inside the engine, the PCM doen't know it's not true, it won't set a code, the PCM will just widen the injector pulse.

If you can't get access to a scanner that will show you the data stream (not just a code reader -I use one from OBD-2.com that's used with a computer, costs @ $120 - best money I've ever spent on a car), you could try swapping the CTS, as it's generally cheap and easy. The O2S is generally easy, but not cheap.

 

Also you could clean out the EGR valve, since build up in there would also decrease mileage, though I think it would only have a little affect. Also are there any other symptoms that have happened recently (i.e: rough idle, high coolant temps).

The other thing is when do you fill up? Do you go off the gas gauge and if so how much are you putting in, cause it could be a faulty gas gauge or float in the tank. Just let us know cause evidently bad gas gauges are pretty comon in these, then you could just fill up using your trip odometer.

The other thing is make sure tires are inflated to atleast 32psi cold and that you don't have a lot of stuff in the back of your truck (dead weight, every 50 pounds decreases gas mileage in the city by like 1-2mpg). Also are you running larger than stock tires? As this could decrease gas mileage and if your speedometer was not recalculated afterwords would result in a speedometer error and an odometer error (reading less miles than you are actually putting on resulting in lower MPG when you calculate it). Hope some of these things help maybe, keep us updated.

 

Also, have you switched from gasoline to E-85? It's got significantly less stored energy, so you'll use more.

 

I don't believe you can run E-85 in blazers. As I recall they are not flexfuel capable. At least I know up through 200 they weren't. A quick online search didn't reveal anything about blazer's flexfuel capability so as far as I know they are not able to run on e-85.

 

Only the 2.2L engine in the S-10 and Sonoma was Flex Fuel compatible.

 

well i checked the coolant today and its pretty nasty looking not brown yet but alot of brown build up in radiator cap and overflow so maybe ill go get that flushed this weekend and clean/replace coolant temp sensor. no e-85 i havent even seen that yet. well thanks guys ill get back to you this weekend tell ya how shes doing

 

I get the same thing in my blazer.