Gas mileage issues

[Frogger]

when i bought my truck about a year ago i was getting about 270-285 miles a tank pumping 89 octane now same gas and i am only getting 250. the truck has 31,000 miles on it and its a 2003. the extremely odd thing about it is i am babyin it more now and going easier on the peddle then i did at 1st. is it time for some tune up work?

[Matt 4.3 TBI]

Tune up certainly wouldn't hurt. Change the spark plugs, air filter, and run some fuel injector cleaner through a tank of gas, see if that doesn't give you back some mileage.

[T Man]

Try your o2 sensor/s first, at least the upstream ones.

[Sparky2263]

Clean your MAF sensor. Not using an oiled filter are you?

[Frogger]

i am using an oiled filter with the intake it doesn't have much oil on it though its not saturated in it. o2 sensor i didn't even think about thats a good idea i will do a full tune up when i get back from basic (leaving in a week) and i regulary run some of lucas's fuel system cleaner through the gas tank as well as an octane booster every now and again the funny thing is on the high way a full tank of gas will still give me the same milage about 365/340 miles depending on how many stops i make on the trip

[Matt 4.3 TBI]

You can do without the octane booster, unless you have some really bad gas. A stock engine doesn't need more than 87 octane, so you could be saving money. If your engine IS knoking on 87 octane without any mods, then this is definitely evidence of another issue. I try to run a bottle of fuel injector cleaner at least every other oil change though. I'm a fan of B12 Chemtool, personally.

I know GM has been shipping vehicles with their 'no service till 100k miles' spark plugs, but I would advise at least pulling a couple out and taking a look at them to see if they have any deposits on them. I've seen those long-life platinum plugs lose the tip of the center electrode as well.

If you're using an aftermarket filter, and it's still relatively clean, you can rule that out. I wouldn't expect O2 sensor would be a problem, but only the upstream sensors will have anything to do with fuel mixture. They are the most expensive components that we've talked about so far, though. Only way to truly check them is to test them with a multimeter. At around $60 each, you don't want to just start replacing these.

[T Man]

You can do without the octane booster, unless you have some really bad gas. A stock engine doesn't need more than 87 octane, so you could be saving money. If your engine IS knoking on 87 octane without any mods, then this is definitely evidence of another issue. I try to run a bottle of fuel injector cleaner at least every other oil change though. I'm a fan of B12 Chemtool, personally.

I know GM has been shipping vehicles with their 'no service till 100k miles' spark plugs, but I would advise at least pulling a couple out and taking a look at them to see if they have any deposits on them. I've seen those long-life platinum plugs lose the tip of the center electrode as well.

If you're using an aftermarket filter, and it's still relatively clean, you can rule that out. I wouldn't expect O2 sensor would be a problem, but only the upstream sensors will have anything to do with fuel mixture. They are the most expensive components that we've talked about so far, though. Only way to truly check them is to test them with a multimeter. At around $60 each, you don't want to just start replacing these.


^^^^^Im with stupid. Wow 60 bucks a piece? Mine are like 25. Thats why I suggested it. How does one go about testing them?

[Matt 4.3 TBI]

Yours/Ours are cheap since they are one-wire units. 2003's have four wires for the sense line, heater circuit, and heater sense line. The sense line will output voltage (very low, between 0 and 1 volt. 14.7-1 mixture will show about 0.5v if you probe the sense line with a multimeter or voltage tester. Low voltage 0.1-0.2 shows a lean mixture, rich will be 0.9-1.0. 1 volt is VERY rich. In normal operation it will swing from 0.2 to 0.9, it's just if it settles at one end or the other that indicates a problem. With the sensor disconnected, it can't alter the fuel maps, and the computer will go into a backup program. Truly the easiest way to test an O2 is to check the voltage of yours, then compare it to a known good sensor, or to the voltage output from a tailpipe probe.

There is a method for bench testing as well. You need to put the sensor in a vise, attach the negative lead to the case, and the positive to the sense line. Then you use a torch to heat up the perforated tip of the sensor and watch the voltage. You should see at least .5 v within 20 or 30 seconds. If that's good, turn off your torch and the voltage should drop.

[Frogger]

hmm i think i will wait till i am done with my air reserve trianing before i start monkeyin around with that too much to do before i leave already but ty ;) ya i will check a spark plug or two on my next day off thanks for the help all!

[imdawrlus]

Tire Pressure!!!!

[Badco]

when i bought my truck about a year ago i was getting about 270-285 miles a tank pumping 89 octane now same gas and i am only getting 250. the truck has 31,000 miles on it and its a 2003. the extremely odd thing about it is i am babyin it more now and going easier on the peddle then i did at 1st. is it time for some tune up work?


Quit racing me damnit!! J/k

Come over to the house today and I'll give ya some Sea Foam. Bring some cleaner and we'll clean out the MAF. Besides, I need to do the same to mine as well. Might as well knock 'em both out. :cool: