96 Yukon lousy mileage

[sterios]

Ever since I did my fuel pump my mileage has been cut in half. New pump, fuel filter, air filter, plugs, cap and rotor. Full fuel system flush and treatment. Had driveline checked and all is well. Checked with Scan tool and it's not storing any codes. I did a fuel pressure test and with key on, engine off it's 66 pds. With key on, engine on it drops to 54 pds. With enging turned off the pressure drops over five minutes to about 42 pds. No visible leakes on lines or tank or behind engine. No fuel in intake plenum. Does anyone have any other ideas? Parking brake not seized on by the way. Thanks

 

[sterios]

Stumped the board

I sure hope there is a prize for stumping all the experts on this board. I finaly figured out why my mileage had gotten soooooo bad so quickly. Turns out it was the Oxygen sensor. Replaced it tonite and the truck runs like it used to. Nice and smooth and the exhaust smells just right. Hope this helps someone out there.

 

[Mike97]

Was the check engine light on? It's unusual for the o2 sensor to fail without throwing a code.

Glad you figured it out. How much did the sensor cost you?

 

[Getwired]

I sure hope there is a prize for stumping all the experts on this board. I finaly figured out why my mileage had gotten soooooo bad so quickly. Turns out it was the Oxygen sensor. Replaced it tonite and the truck runs like it used to. Nice and smooth and the exhaust smells just right. Hope this helps someone out there.

No more fire shootin' out the tailpipe, eh? :smilielol: Glad you found the issue!

 

[sterios]

o2 sensor

No codes on the computer. I had done everything else and did a little research and found it's common for an O2 sensor to start failing and affecting mileage and smell of exhaust so I swaped it out and it worked. It cost 93 bucks canadian at Crappy Tire.

 

[96ProCompTahoe]

you replaced one O2 sensor or all 4?

 

[sterios]

o2

I just replaced the front one. Figured that was the one the computer uses to set air/fuel mixture. The one behing the cat determines if the cats working. Not sure if I have four of them though. My trucks doesn't have duel exhaust.

 

[96ProCompTahoe]

its got 4, mines a 96, dual pipes off the exhaust manifolds, the left crosses over to the right side, they both go into the muffler and then it transfers into one pipe after the muffler. unless yours has some other exhaust put on it post factory.

i was going to say that $93 installed for 4 of them is a good price... haha

 

[sterios]

sensors

Yeah you're right. I just looked and mine is just like yours. I guess I lucked out with the one I replaced. Might do the other one too I guess just to keep things even. I'll wait for them to go on sale though.