KryptoKid

Hello all,

I Just recently replaced the upper O2 sensor and reset the code on my 01 4runner. Before I had the CEL I was getting between 300 and 350 miles to the tank depending on my driving. I just went on a 5 tank road trip and I was lucky to get 280 I would say between 230 and 280 to the tank now. I am not sure what elso could be causing this, but I am curious what other sensors help tune for gas mileage? Does the lower O2 sensor help tune or is it just a secondary sensor for the upstream? Also what other components could effect gas mileage that drastically? I am going to swap plugs, wires, cap and rotor as soon as I have some cash. Any other ideas?

Thanks in advance.

-Me-

rdharper

Why did you replace the O2 sensor in the first place... given that you were getting excellent mileage?

Nate08

Implying had didn't get that good gas mileage once he got the CEL.

Spark plugs play a large part. Even maybe your oil. I went from Mobil1 Synthetic to Valvoline for this oil change (for $ reasons and experimenting) and have lost 2.5 MPG. I'll defiantely be going back to synthetic.

MTL_4runner

First, there's no cap and rotor on that truck. I hope you also used a Denso brand air/fuel sensor (01's use an A/F sensor, not an O2 sensor in front of the cat) and reset the ECU when you changed it (just pull the neg batt terminal for 5 mins). Lastly, you might also want to try cleaning your MAF sensor with brake cleaner (again reset the ECU if you do this) and switch to synthetic oil (it's not just hype, it really does add to your fuel economy).

element

With the recent temperature drops, make sure your tires aren't low. They can make a big difference. I also agree with Jamie, go with OE sensors for long term savings and reliability. They make a MAF cleaner spray now that may be safer around plastic pieces. I got some at Advance.

It might not be a bad idea to calculate your fuel economy by miles per gallon instead of by the tank. By the tank you are relying on the accuracy of you gas gauge (assuming you’re not driving it dry and walking for your first gallon every time ) and how full you get the tank. On all off my cars I can usually add at least another gallon after the pump shuts off automatically.

The mileage you are reporting right now shows a pretty large variance. With an 18.5 gallon tank:
350 - 18.9 mpg
300 - 16.2 mpg
280 - 15.1 mpg
230 - 12.4 mpg

If you fill your tank up and reset the trip, you can divide the number of miles you drove by the number of gallons you pump on the next fill up to get a more accurate reading. I try to keep a running total going for 1000 miles to get a good average.

KryptoKid

I am currently running the Valvoline Max life synthetic, but I am about 3800 miles into this oil and am about due for a change. Maybe that will help, I will check soon.

MTL good looking out on the cap and rotor. Haven't had the truck long, but probably would have figured that one out at the autoparts store.

A/F sensor or O2 sensor, tomato tomaato, close enough you got the point now it is just semantics. No it isn't a Denso brand I believe it was a Bosch (only one I could find locally) and I used a code reader to delete the codes and reset the ECU. I will give my MAF a good once over later this week as well.

Good idea with checking the tires, they are a little low. as far as computing the milage, I am actually not relying on the gas gauge at all. I normally top off the tank and pay no mind to how may gallons I use, but I always reset the trip, refuel once the gas gauge shows first light and see how many miles I get to the tank. It is a fairly constant system so it works as a good form of measurement for me. converting to MPG, I would need to know how many gallons of fuel I am actually adding to the tank and really plus or minus a mile per gallon doesn't matter to me, but plus or minus 5MPG is a sign of a problem and therefor does matter.


Thank you all for your replies. I will look into all of these and see what I can come up with on the next tank. To be continued....

-Me-

hopper

That may be the problem. If you search you will see that other people have had problems with Bosch. If you cant find info here you may find some on TTORA.com

KryptoKid

great, that is wonderful to find out after I have put a few thousand miles on this one.

MTL_4runner

O2 sensors and Air Fuel Ratio sensors (or A/F sensors for short) are not even close to the same sensor (it is litterally like comparing dogs and humans and saying they "yeah, they're both mammals, same thing"). A little quick search will find you countless threads of info for you to read on the subject.

You also made a big faux pas by installing a Bosch sensor, again plenty of info on that issue on YT also, quick search will yield bountiful info. If you installed any other Bosch stuff like spark plugs or the like, take it out and install NGK or Denso brands ONLY and there's a reason for it.

icerunner

Hey,
O2 sensors are "touchy"... IF your 02 sensor was "dropped" or mishandled at any time (shipping or other wise) it may now be defective....one hard drop and that thing will not work right...
Any codes?

KryptoKid

Ok did some research and I still don't seem to care about the difference between the two. Like I though they are used to detect oxygen in exhaust gasses. I have done some searching on the bosch sensors and I have found very few posts on any message boards including this one confirming what you are saying. I am not saying that you are wrong, I am just saying that I am having a hard time believing it.

I also don't understand how Bosch could stay in business with all of there gear being complete garbage. I have used many bosch products with no problems, so I am having a hard time believing that everything they make is no good. I am going to spend a few weeks trying other options, then I will make a bigger attempt to see at trying to believe the problem is the brand name. Especially when most of these products are all made from the same company and renamed and repackaged for resale.

As far as the sensor being damaged, It wasn't while it was in my control but I don't think returning it now is much of a possibility so I will try anything else I can come up with first. I would rather save the extra couple hundred dollars for a new bumper.

-Me-

One_96TR4

It's not the fact that Bosch makes garbage because they don't. I have a mazda MX6 and it has bosch plugs and o2's and they work great. It's just that for the 4Runner they don't seem to be the best. There have been numerous ppl that have tried Bosch O2's and had bad results and then tried a denso or NGK and it worked great. This car just seems to be very particular about certain parts.

MadCityRich

Absolutely. It's about how the vehicle is designed. I have an older BMW and it hates anything but Bosch for electronics. There's only a single type of spark plug that Bosch makes that actually works for the engine - the stock design from the factory. Anything else causes problems.

So it's not Bosch, it's that Toyota designed things to run under Denso or NGK specs.

MadCityRich

KryptoKid

So I doubt schuucks has a return policy on used o2 sensors? Any ideas?

One_96TR4

They might if it's "defective". Would definitely be worth looking into.

bruzryoda

on your mileage, and or, dont buy 85 octane in Idaho. it " WILL" destroy your sensors. as if 87 was not bad enough...... as far as what they call the cheap stuff here i will just leave that alone.............. (knee) (kick) cough.......... mormon gas........... did i say that?? oopppsss!!!!!

KryptoKid

LMAO, I can't believe someone else believes this too. I never buy less than 91 in that state. i am going to call the part shop today and see if they can hook me up.

MTL_4runner

1) I don't think I ever said Bosch parts are garbage
2) The sensors are not all made in the same factory and just rebranded

Here's some good reading for you on the compatability of Bosch parts and Toyota engines:
https://www.yotatech.com/search.php?searchid=4069956
https://www.yotatech.com/search.php?searchid=4069967

KryptoKid

Look I am not trying get into a forum pissing match. I am definitely not trying to put words in your mouth, but I am also not too eager to except anything as an absolute.

thank you for the replies, i will do some follow ups and get back to you all, maybe I will be the next in line yelling no to the bosch/toy combo.