Losing 50 miles per tank on mileage - help!

[DjLarroc]

Hey guys, new here but was a member of TF.

Got a 2000 Tahoe 4x4, 5.3. 184k. Runs like a champ, but in the last month or so, the mileage has gotten terrible. I haven't noticed anything different about the truck. Normally I'd get about 300-315 per tank, and fill up would be about 21 gallons (15mpg). My last fill up (yesterday), I only got 260 on about 20 gallons (13mpg). My last 2 fill ups prior, were about the same. Slightly better.

The truck does have a hesitation on acceleration. If I step on gas more, it does nothing. Only way it goes away is if I let off gas, and slightly try to accelerate. Sometimes it catches, sometimes it keeps doing it until it feels like accelerating (Injectors?). It has always done this though.

Any advice appreciated. TIA.

 

[Copper&Black]

I would start with a through visual inspection of the injectors. Replace the inline fuel filter, and run a bottle or two of fuel system cleaner. Then run your numbers again to see if it improved. Have you hooked it up to any computer to see what codes you might be getting?

 

[BlueTahoe2001]

Run some Sea-Foam through maybe 2 tanks of gas, Replace the fuel filter, Plugs, and Wires.

See what your results are after you do this and then go from there if it doesn't seem to get better.

 

[jhellwig]

Winter fuel could be some of it.

 

[DjLarroc]

Thanks for the quick replies guys!

I did new plugs (OE) at 177k. Ran seafoam around 180k.

No CE codes. Will anything come up anyway?

I'll replace the fuel filter. Only recent work, was oil pump went out. Got that fixed. Took on a road trip and avg'd about 18MPG on that trip. Best I've gotten. Then, now, this crappy mileage.

 

[yooformula]

I would try the fuel filter like mentioned, try cleaning the maf sensor then maybe the 02 sensors.

 

[dropmech]

Air filter?

 

[DenaliAK]

Where do you live and are they adding ethanol or any other winter additives to the fuel? Do you have winter tires on now, which because of their design tend to be less efficient? Is it cold and do you autostart or otherwise warm up the truck? That one kills my winter mileage...warming up the car. Tire pressure ok?

Just a couple of other ideas....

 

[Rivieraracing]

Sounds like your cats are crapping out or plugged up, when mine in my Blazer finally plugged up, the more I stepped on the gas the slower it actually went. Try tapping on them and see if you hear anything loose or rattling around in there. Does you exhaust sound any different, kinda like it is breathing through a scuba snorkel? Decrease in exhaust flow out of the tailpipe? Truck running any warmer than normal?

 

[yukonjacks]

Are you letting your truck idle longer during the colder mornings, no offense but winters are notorious to drag down gas milage from crap you may over look. Also your truck has to run harder due to the viscocity of the oil when its cold