Changing Oxygen Sensor Improved MPG

[ziggyor]

Greetings all. New to this site from "that other place". After reading your comments on various notes on improved mpg by replacing an oxygen sensor around 80K miles, I decided to give it a try evan though I have no codes showing. I bought my 02 TB LT 2 months ago with 197K miles from original owner with meticulous maintenance records. It was getting ~ 18MPG on the highway which aint too bad. Records showed it still had the original sensor in it. I read in your threads the manifold sensor should be replaced about 80K miles. Per your direction I ordered the AC Delco Sensor and an oxygen sensor socket from Amazon.

I did the start engine for 20 seconds, wait 10 minutes, spray PB Blaster, wait 4 hours, thing. Using a 3/8 drive ratchet the original sensor came right off. The new sensor came with anti-seize on it. Screwed it in by hand, gave it another 1/8 turn nudge with ratchet to compress the compression washer like spark plugs have.

Filled gas tank and went for a 150 mile ride mostly on highway with some inclines. Filled it again at the same pump.

The old sensor had some differant color schemes on it as you rotate the tip but nothing that would cause a code to show.

Bottom line my milage went from 18MPG to 19.5MPG with a new sensor.

Thanks so much for the advice.

 

[The_Roadie]

Welcome, and thanks for the report! Did you get a scan tool to look at the data? About the only thing that a sensor can do without immediately throwing a code is get sluggish. So the data will go from high to low voltage less than once per second.

 

[ziggyor]

Welcome, and thanks for the report! Did you get a scan tool to look at the data? About the only thing that a sensor can do without immediately throwing a code is get sluggish. So the data will go from high to low voltage less than once per second.

No I don't have access to a scan tool. All I have a code reader.

 

[triz]

You should be able to get a bit more. I'm running on the original sensor and still get about 20.5 MPG on the HWY. 65-75mph.

 

[ziggyor]

yours have tow package gearing?

 

[hockeyman]

Damn! Since purchasing my '03 Envoy XL last July, I changed my spark plugs, air filter, all fluids, IAT sensor, both O2 sensors, fuel filter, serpentine belt, cleaned the TB, seafoamed, new tires (all filled to spec), and probably some other things that I cannot think of at the moment, and I'm still averaging 11 mpg in the city and 14 mpg on the highway.

No codes in the OBD system, suspension is good, brakes are good and they don't drag, ...

I wouldn't consider myself a lead-foot, although I DO hate it when Asian and old-folk (100 yrs old and up) drivers are in front of me. I try to get away from them asap! Other than that, I keep up with the flow of traffic most of the time. I seriously do not know where the low mpg's are coming from, or what else to change to improve them...?? The only time I use the a/c is when the wife is riding along with me, and that's not that often. She has her own car.

 

[CaptainXL]

Here is a good article about checking O2 sensors. With a fully warmed up engine, at 2500 RPM the O2 sensor frequency from low to high should be at least 8 cycles in ten seconds or 0.8 Hz. This will tell you if it is lazy or not.

http://www.autoshop101.com/forms/h58.pdf

 

[CaptainXL]

Damn! Since purchasing my '03 Envoy XL last July, I changed my spark plugs, air filter, all fluids, IAT sensor, both O2 sensors, fuel filter, serpentine belt, cleaned the TB, seafoamed, new tires (all filled to spec), and probably some other things that I cannot think of at the moment, and I'm still averaging 11 mpg in the city and 14 mpg on the highway.

When this happens you have options. A ton of stuff can be checked. To me it sounds like you are staying in open loop for some reason. I would get a scanner on it asap and check the fuel trims. Make sure the torque converter lockup is working as well. Also make sure you are at the proper RPM's for a given speed on the highway.

 

[ziggyor]

Hockeyman... When you cleaned the TB did you remove it and clean the backside? Right after I bought it I also replace my Cam Position Sensor because of a code and I replaced my Cam Postion Solenoid. When I removed solenoid to clean it like threads recommend, The internal gasket was leaking oil onto its electrical connector. Cost me ~ 18 bucks for the sensor and 50 bucks for a solenoid. The electical connecor and pins HAD A TON OF OIL ON THE CONTACTS.

 

[hockeyman]

Hockeyman... When you cleaned the TB did you remove it and clean the backside? Right after I bought it I also replace my Cam Position Sensor because of a code and I replaced my Cam Postion Solenoid. When I removed solenoid to clean it like threads recommend, The internal gasket was leaking oil onto its electrical connector. Cost me ~ 18 bucks for the sensor and 50 bucks for a solenoid. The electical connecor and pins HAD A TON OF OIL ON THE CONTACTS.

Yes, I completely removed the TB when I was cleaning it. I even removed the butterfly piece in the middle, just so I could thoroughly clean around it. The inlet looked like it was brand new when I was finished. The PCM fuses were pulled during the time of cleaning, and it reset itself when it started up again.

I haven't checked the Cam Position Sensor or Solenoid yet. I guess I'll go ahead and order/replace them, then check what CaptainXl said. I have a hand-held scanner, but I'll need to take it somewhere to have the fuel trims adjusted properly since my scanner does not have that option.

I'll be up on the highway with it tomorrow, and I'll post the speed-to-rpm ratio once I get home.

As always, thank you for the advice!

 

[ziggyor]

my 02 TB LT with tow Pkg does ~ 68 MPH on the highway at around 1900 RPM

 

[CaptainXL]

my 02 TB LT with tow Pkg does ~ 68 MPH on the highway at around 1900 RPM

Sounds good. Seems like the transmission is working ok.

How is the power? Does it accelerate well? Has there ever been times when it is hesitating, bogging down or feel like it's generally low on power at all?

Smell the exhaust from a cold start. Like in the morning. Does it smell rich? Notice any smoke from the tailpipe? How is the oil level? Are you burning any?

Is the engine ever hard to start? Does it crank over for more than a second before starting? Do the crank times seem different between starts?

Also what tires are you using? Are they the original size and speed rating?

 

[ScarabEpic22]

my 02 TB LT with tow Pkg does ~ 68 MPH on the highway at around 1900 RPM

Thats not specific at all, every single GMT360/370/305 has the factory tow package. The only things that change are engine, gearing, and 2WD/4WD/AWD. So you'd have an 02 TB I6 4WD with 3.42, 3.73, or 4.10 gears. Judging by those RPMs, you have the highway (not towing) 3.42 gears. My 02 I6 4WD 3.73 spun 2000rpms at 65mph with stock size tires.

 

[Wooluf1952]

To ziggyor:

Welcome


In case you haven't heard:
http://gmtnation.com/forums/topic/218-welcome-to-gmtnationcom-heres-the-story/



To hockeyman:

From all I've read, anything over 40-45 mph with the windows open, hurts MPG's more than running the AC.

 

[hockeyman]

To hockeyman:

From all I've read, anything over 40-45 mph with the windows open, hurts MPG's more than running the AC.

Yeah, I've heard that too. I think Mythbusters did an episode on that too. But I've been calculating my mileage even during the winter months when I had the windows up. I think I can still improve the mpg's during the summer months, even while on the highway with the windows down and the a/c on full-blast. Getting 14 mpg's on the highway is horrible. I'm actually understating 14 because it's less than that most of the time.

I know the questions weren't directed at me, but I'm going to respond to Captain's thread;
- No loss of power, ever, and the acceleration is fine. Starts great every time, even when hot.
- No smell from the exhaust, and the only time it spews any kind of smoke is if/when I press the pedal to the floor while highway traveling. No other times though.
- My oil level has "maybe" gone down about 1/2 qt. since I last changed it back in either late January or early February of this year. I added oil last month, but it was only a little bit, and I only added it because I like the oil levels to be perfect.
- The tires I have are Toyo Open Country A20's and they're 10 months old. Installed (brand new) in September of 2012. They're also very quiet on the highway!