All you motor heads- do I need a new o2 sensor ?

[fatnslow]

I have a 00 Honda Odyssey knocking on 200K that seems to be getting shitty MPG, honestly I don't pay too much attention but my recent long haul came in at around 19 MPG where at one point I remember around 22-24 MPG in former glory days a few years back. Plugs/air filter/coils are all good and not throwing any codes but the o2 sensor is original. Do i just replace the damn thing ? I think they only run about $30 and not too difficult but I'm feeling pretty lazy right about now.

[powbmps]

It will throw a code if the O2 sensor isn't working properly. Probably a lot more difficult than you think too. At 200k, it has probably become one with the exhaust. Those things are a bitch to get out.

Is it running alright otherwise?

[DBdude]

when my o2 sensor went on a volvo 240, the thing ran like shit

[east or bust]

I had to change an O2 sensor on my blazer a couple months ago. Was wondering why I was getting shit mileage for a while then it finally threw the code, mileage returned to normal after sensor was replaced. So I would not discount the sensor as being the problem. The engine was also running a bit rough before the replacement as powbmps mentioned.

Granted my blazer sits higher than your Odyssey, but the job was not difficult to do once I pulled up on a curb to gain additional clearance and allow me to put more torque on the sensor, I had 175K on the sensor at the time of the job. YRMV

[that dude who did that thing]

You're worried about the MPG in a 17 year old minivan? OK.

A 10-20% drop in mileage over a period of 17 years could be caused by all sorts of inefficiencies arising as a motor gets older. Rings leak, valve seats get fouled, accessories draw more power, rising exhaust back pressure. You could also be using shitty gas. Your driving patterns might have changed.

Can't imagine any harm from changing out a 17-y-o O2 sensor, except the few bucks you spend on it. Butsi there a reason you focused on that as the potential source of your fuel efficiency drop?

[willywhit]

having a similiar problem with my ford focus svt. runs like it's running on 3 cylinders, bad gas mileage. pretty sure it's gummed up the cat in the exhaust. let me know how it turns out.

[MagnificentUnicorn]

It will throw a code if the O2 sensor isn't working properly. Probably a lot more difficult than you think too. At 200k, it has probably become one with the exhaust. Those things are a bitch to get out.

Is it running alright otherwise?

Bad or failing O2 sensors don't always throw codes. If you look at a lot of FSMs they recommend new O2 sensors around 100k miles.

[Mazderati]

O2. Tire pressures. Alignment. How much shit is being hauled around.

[fatnslow]

You're worried about the MPG in a 17 year old minivan? OK.

A 10-20% drop in mileage over a period of 17 years could be caused by all sorts of inefficiencies arising as a motor gets older. Rings leak, valve seats get fouled, accessories draw more power, rising exhaust back pressure. You could also be using shitty gas. Your driving patterns might have changed.

Can't imagine any harm from changing out a 17-y-o O2 sensor, except the few bucks you spend on it. Butsi there a reason you focused on that as the potential source of your fuel efficiency drop?

Newer clean platinum plugs(oem spec), clean air filter, clean throttle body and good coils. what else is there that is super easy ? I understand the motor and catalytic converter are getting a bit tired but not about to rebuild the damn thing. These also need periodic valve adjustment but I hooked up a vacuum gauge and it pulls a steady 21 so I'm looking at cheap and and easy things first.

[uglymoney]

A bad thermostat will make the engine run cool and give you bad mileage but it won't throw a code. A bad o2 sensor will throw a code. No code then leave it alone.

[papapoopski]

Clean the MAF sensor?

I just changed out an O2 sensor a few weeks ago, took 10 minutes. If yours is original, good luck getting that out.

[basinbeater]

You say plugs are good, even if you just put new ones in, pull a one and look at its condition. If it black and sooty, you are running too rich, and o2 can try to compensate, but once the car is up to temp, o2 sensor really is only used to try to fix idle mixture. So if it is black and sooty, you may have other issues related to fueling or metering air. 19 mpg isn't too bad, and maybe you are just putting your foot into it more to keep up with faster traffic. Seems like average speeds have picked up around me, hell, the in town speed limit on freeways is up to 70 now, and the open country speed limit is 80 now. People are driving faster.

[Timberridge]

Use this opportunity to convince the wife to get rid of the minivan and get something more manly.

[fatnslow]

Use this opportunity to convince the wife to get rid of the minivan and get something more manly.

uhm, I drive the minivan and it fucking rules. Getting blow jobs in a minivan is much easier than a SUV or a head gasket time bomb Subaru. Just recline in the second row captain's seats with tinted windows and enjoy.

[The Tortoise]

It's also winter. The cold fucks with mileage and 19 doesn't sound too terrible for a Minivan.

[fatnslow]

You say plugs are good, even if you just put new ones in, pull a one and look at its condition. If it black and sooty, you are running too rich, and o2 can try to compensate, but once the car is up to temp, o2 sensor really is only used to try to fix idle mixture. So if it is black and sooty, you may have other issues related to fueling or metering air. 19 mpg isn't too bad, and maybe you are just putting your foot into it more to keep up with faster traffic. Seems like average speeds have picked up around me, hell, the in town speed limit on freeways is up to 70 now, and the open country speed limit is 80 now. People are driving faster.

I have done the same I-70 drive for 18 years and this trip seemed to have lower MPG that usual and the plugs look used but clean. I probably drive a bit slower than I use to a few years back, freaking getting passed by grannies doing 90 in Montana. I usually keep it under 80 even in Montana.

[Timberridge]

uhm, I drive the minivan and it fucking rules. Getting blow jobs in a minivan is much easier than a SUV or a head gasket time bomb Subaru. Just recline in the second row captain's seats with tinted windows and enjoy.

Perhaps some semen got into the control module?

It ain't no Sonata. That shit gets you an invite inside...after the kids are in bed.

[El Chupacabra]

It's also winter. The cold fucks with mileage and 19 doesn't sound too terrible for a Minivan.

That, plus winter fuel.

[basinbeater]

Take the roof box off...

[Timberridge]

That's where he keeps the condoms.

[powbmps]

Clean the MAF sensor?

I just changed out an O2 sensor a few weeks ago, took 10 minutes. If yours is original, good luck getting that out.

Good call on the MAF. Get a can of MAF sensor cleaner, pull the air filter box, and spray it off. Cheap and easy. Worth a shot.

[fatnslow]

Good call on the MAF. Get a can of MAF sensor cleaner, pull the air filter box, and spray it off. Cheap and easy. Worth a shot.

I'll give the MAP sensor a shot of cleaner. It's super easy access on top of the throttle body on this car.

[fatnslow]

Perhaps some semen got into the control module?

It ain't no Sonata. That shit gets you an invite inside...after the kids are in bed.

Kids are 19, 17 and 14, they NEVER go to bed before midnight. Bought an old Benz as a pimp ride but the kids hjacked it from me so I'm back to the Hummer sled.

[fatnslow]

Take the roof box off...

NOT POSSIBLE, the mistress rides in that thing to provide rest stop action in the woods on long family road trips.

[El Chupacabra]

NOT POSSIBLE, the mistress rides in that thing to provide rest stop action in the woods on long family road trips.

It's about time you got a roof box for Aunt Edna.