Getting Bad Gas Mileage? You May Need A New Air Fuel Ratio Sensor

Scotty Kilmer, mechanic for the last 46 years, shows how to replace a bad air fuel ratio sensor on your vehicle.Getting bad gas mileage? You may need a new sensor, but this video shows how easy they are to change.

Things I used in this video:
7. Common Sense

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[scottykilmer]

Things I used in this video:
7. Common Sense

🛠Check out my Garage to see what I use every day and highly recommend:

❗️Check out the Scotty store:

👉Follow me on Instagram for the latest news, funnies, and exclusive info / pics:

[jovethegreat]

THIS DUDE MADE ME INTO A MECHANIC
SO FAR
ALTERNATOR
SPARK PLUGS
AXLES
BRAKES
HEADLIGHTS
TRANSMISSION FLUID
have all been changed cause he inspired me

[scottykilmer]

as it goes away with AC on, it's the idler bearing on the clutch that is wearing out. it only runs on that bearing when off, when on it runs on the internal bearings of the compressor itself. If your manifold isn't cracked, remove it and replace the gasket there. Running it that way can damage the engine seriously over time by messing with the air fuel ratio inside and burning pistons out

[scottykilmer]

O2 sensor systems are very complex feedback computer driven complexities. Probably best to see a mechanic like me to analyze it, as scores of different things can trip that code.

[danmatthews]

Yes, the O2 sensor do wear out. anything  with more than 100k miles should be changes. The senors that are before the cat converter regulate the air fuel and can cause a emission  test failure. The o2 behind the converter is for complience testing only and rarely fail. . It is easier to remove when the exhaust is warm or hot, but wear gloves. Also you can cut the wires off ( Engine Off) to place a 6 sided deep well socket over it. Some bigger spark plug sockets do sometimes work. You can buy a special socket with a slot to allow the wire through.

[segbachan]

I just replaced my O2 sensor in 2012 Buick enclave with the original AC Delco sensor and I'm burning much more fuel..car runs good tho..no codes I may have to run it some before I may notice the change

[manthonychavez]

Scotty, I love your videos and have learned a lot! I diy stuff like tire changes and small repairs.

I ask that you be more specific when it comes to the "generations" of cars. In this video, that would mean specifying the years (e.g. '95-'98) in which the have been made in car parts/systems.

If you don't know or it's not really that cut-and-dry, then OK. If you do, I would really appreciate the information for future videos.

I remember in a video you said that certain changes were made in "late-model cars", and I didn't know what that meant. But now I am asking.

Thanks Scotty

Michael

[paulvhayste]

Hi Scotty,

I have a Mitsubishi Lancer GLXI '98 with a manual, 1.6 4G92 EFI engine. Lately, I've noticed a significant gas mileage drop on it. I usually get 8km/liter on city driving (stop-and-go traffic) with the aircon on (I live on a tropical country so this is a must, especially during daytime) and 10km/l with continuous driving.

However until recently, my city driving mileage dropped to 6km/l. The Check Engine light doesn't light up but my engine stalls almost immediately during startup. You have to rev up the engine for at least 10 seconds and wait for it to "warm up" for about a minute before it will have a stable idling. Otherwise, the engine will stall almost immediately if you try to move the vehicle in the first gear.

One of my driving habits is to put the clutch on neutral once I gain my car's cruise speed (around 30-40 km/h) and just "free wheel" instead of revving the engine, especially on short distances or when I'm near a traffic stoplight (for saving a bit of fuel) Recently, whenever I do that, the engine stalls and I have to shift to 2nd/3rd gear and step on the gas to start it up again while moving.

I just had the oil changed and engine tuned up (they only adjusted the valves) less than two months ago. Can you help identifying what's wrong with my car? :(

Thank you and more power!

[scottykilmer]

have all the sensors and live data analyzed by a guy like me, many things can go wrong, from weak maf sensors to leaking injectors.

[scottykilmer]

they are for test running a vehicle to analyze if it's working correctly, using the dyno and a five gas analyzer for exhaust gas analysis

[BasementBen]

Love how Scotty goes "Ooommph" even after unplugging the large connector :D

[johnjr]

Hi, I live in the middle East and drive a Nissan Pathfinder SE 2010 Model. I had noticed a mild hike in fuel consumption couple of years ago but as of now it’s even worse. On a full tank, I used to get about 525 Kms initially and that dropped down to 450 couple of years ago and now I barely get 300 Kms . A month ago I replaced the spark plugs, got the engine tuned up, injector cleaned, air filter replaced, air flow sensor replaced and drove multiple times on a full tank to check if there was any difference at all, but it’s still the same. The Garage I gave to is a reputed one and they say that they find no other fault. I even had Nissan take a thorough check to diagnose the issue but it’s still the same. The air flow filter was replaced at Nissan and I was told that the issue would be resolved…..but it’s still the same….I would say that it’s getting worse. I am seriously thinking of giving this car up ! My driving pattern is the same as it was when I got the car new and I don’t carry heavy language at all as these were some of the tips given on some tube channels…. Please help

[scottykilmer]

over 20 different things can do that, those are complex feedback systems, measuring fuel, air, vacuum leaks, computer injectors pulse rate, and many other things. Probably time to see a guy like me to analyze it, OR, if it runs fine, ignore it. Sometimes just cleaning the injectors helps though.

[tunespt]

Two things, clean the EGR with carb cleaner AND check the electrovalve for proper function, sometimes the electrovalve triggers an CEL and sometimes don't, depends on the car and ECU, but EGR valves do trigger the CEL to come up. to check the electrovalve, measure the voltage going into it while the vehicle is moving (broken cable) and if the winding on the valve is not open, use an ohmmeter, usually 15 ohms (varies). Vacuum leaks also cause problems in this area, check for them too.

[AuMechanic]

Low MPG, spitting O2, trim or update codes.
First thing to check is the oil filler cap.
I just did a vid on a V6 that gradually increased over about 2 years city driving from 23 MPG (10 L /100km) to 18 MPG (13 L /100km) till it showed the MIL
Oil cap wasn't loose but the oring had gone hard enough to suck air. (see the video)
New oil cap and its back down again over another 600 Mile (1000 km driving), no other work done.
Took all of a minute to swap including lifting the hood and closing it again.
Been a qualified mechanic since 1976, and IME more often then not its the simplest things that are the root of most problems.

[charleslove]

I put one in my 01 v6 explorer I’m getting 24 miles per gallon now with the AC on well worth the money

[polelowpass]

I recently replaced both Air/Fuel ratio sensors (before and after the cat) on my VW Golf MK4 2.0 Highline Automatic. It made a very noticeable difference in throttle response and power output. Looking forward to see if it makes any difference in fuel efficiency long-term! :-)

[eddieb.]

This dude right here is the type that u don't fuck with or he'll charge ur ass so much you'll be on the corner hooking

[scottykilmer]

dynos are for pro tuning, worth it if you really want it done right.

[scottykilmer]

fix the grinding first, if pads are worn out, calliper may be sticking. Trac and ABS are complex, if they need further work after fixing the brakes, many people live without them working, as it goes back to normal non abs braking when those systems break down, that's the failsafe mode.