Horrible MPG

[Drew907]

So I have a 2001 Tahoe 5.3 4x4. It had a tuff life till I bought it. It’s got 180,000 miles and holding up well. My issue is my gas mileage is horrendous. Getting between 7-9 mpg in town. Now I live in AK and it’s 10-15* daily this time of year so it gets idled a lot to warm up. In the last 2000 miles I’ve changed
-plugs and wires
-oem fuel pump and new filter
-oil change with quality oil and filter
-intake air filter
-cleaned throttle body
-big 3 upgrade for other reasons
-new battery
Right now I have a check engine light on for a bad car on bank 2. On my scanner it’s showing that the front o2 sensors are acting normal. At idle it has a bad hiccup that feels like a fuel issue or vacuum leak. I’ve looked over the intake manifold with a fine toothed comb and found no leaks. Fuel pressure is right on the money at idle and with rpm.


I’m stuck on what to check next. I don’t mind throwing parts at it. I want this rig perfect. In the summer we put on lots of highway miles during fishing trips.

 

[Mudsport96]

If you have alot of idle time thats possibly the reason. My wife lets ours idle long enough when i hop in it the readout shows 9ish mpg. So my guess is thats a big part of your deal too. While i would check that o2 code and fix it, l dont think bank 2 will have much affect on mpg

 

[OR VietVet]

Same type of recent problem with my old 2002 LT. Idled bad in gear and a stutter from a stop. Bad sensor. May also be old enough that the cats are failing too. This is a problem with an older NBS with 180k miles. Cats old enough to not be efficient, no matter how many new sensors are installed. Replaced all 4 sensors and problem solved. I would also be worried about this: https://www.rockauto.com/en/moreinfo.php?pk=1298772&cc=1371620&jsn=2512. There are a couple of choices, so check the application at RA for the correct one.

 

[wsteele]

O2 sensor issues can force the engine to stay out of closed loop. Closed loop allows your engine to trim fuel flows very precisely.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics, please.

 

[Fless]

O2 sensor issues can force the engine to stay out of closed loop. Closed loop allows your engine to trim fuel flows very precisely.

^^^ THIS. And get a reading on your short- and long-term fuel trims, both banks, with a scanner. Idle and 1500 RPM. They can tell you a lot.

 

[Wylie_Tahoe]

Bank 2 would the right side of engine, as in for cyls 2-4-6-8. What code says the o2 is bad?

Have you cleaned the MAS? Just dont blow it with compressed air.

 

[exp500]

Fuel pressure regulator, and/or relay.

 

[BentleyArnage]

^^^ THIS. And get a reading on your short- and long-term fuel trims, both banks, with a scanner. Idle and 1500 RPM. They can tell you a lot.

 

[BentleyArnage]

60k plus on the sensors? Replace them. They do all sorts of things that don't set codes. Just trash them like spark plugs. It's been a common thread with O2 sensors since the beginning.