I was wondering how you can tell if the O2 is working or bad? does it affect your gas mileage? any recomendations on putting on a better intake and exhaust, to help it breath. I would like the extra HP. also what is the cat converter for. do you need it for emissions?

Not sure about the o2 sensor, but the catalytic converter is for emissions. It element inside gets very hot and burns off excess pollutants. Whether or not you need, depends on your state's emission laws.

If your HO2 sensor is not working, you will get a "Check Engine" light. It will affect your mileage if it is not working.

http://www.autoshop101.com/forms/h37.pdf

http://www.autoshop101.com/forms/h44.pdf

thanks that answers my questions. i dont get a check light so i guess i am good there, and i was thinking about a better exhaust for increased HP and was wondering if i needed the cat. conv. any suggestions on a better intake and exhaust system and est. cost. also i can only get 18mpg / 300 miles to a tank , same on 4 fill ups. any ideas

Actually, you want to check how fast does your o2 sensor respond.
Just because you don't have c.e.l. doesn't mean its working well.
Hook up a multimeter, then have someone rev the engine,
and see how the voltage changes, if it changes to slowly, then its bad.
I suggest changing it every 100,000 miles for fuel economy....

I will replace it and forget the test. the truck has 120k so it is probably about time. i want to get better than 18mpg.

***** still looking for any info on the intake and exhaust*******

For the intake - do the deckplate mod - - - -http://www.wattora.com/Mods/deckplate/.
It is cheap and works the best. As for exhaust - find a sound you like and go with one. It may or may not improve the MPG. Minimal gains in the HP dept. Good luck.

For the intake - do the deckplate mod - - - -http://www.wattora.com/Mods/deckplate/.
It is cheap and works the best. As for exhaust - find a sound you like and go with one. It may or may not improve the MPG. Minimal gains in the HP dept. Good luck.
:iagree:

Hey ekspc !!!! What happened when you changed the O2 sensor???? any mileage improvement????
Wich engine do you have??? I have the V6, and I only get 200 miles per tank, mileage is awfuly bad. Any suggestions???? thanks

between vacation and visiting family the O2 has been put on hold. the weather has been bad also, so ... I know someone that has an 86 w/ turbo and only gets like 14-16. he has bigger tires. so I think that makes a difference.
my engine is the 24RE and the tires are like 30.5x??x15
I will post the results when work is done. I have run some Marv Mystery Oil and that helped. also the engine is getting broke in again. the previous owner sat on the truck for years with very little use.

What truck to you have? You need to refer to the OEM specs for replacing the O2 sensor. Also, do be so depend on the early year import OBD(so they call it) system. My truck is an 86 and runs rich. My check engine light didn't come on. And to test the o2 sensor, you should an oscilloscope. If you are going to use a meter, use an analog, the signal from the o2 sensor should change 8-10 a sec. Your dmm won't be able to register this fast.

As for my running rich problem, the problems could be endless, and with these trucks, if your not running a 96 and up with standard OBDII, you will have to go and check each compent.

I believe toyota recommends changing the o2 sensor every 60 thousand miles

anything that come stock with a catilitic converter is required to have one, big fines if ya take it off.

the tires are probaly a good part of the bad milage. but i would also check the coolant temp sensor. if that is bad your truck will run rich and mileage goes strait to hell.

Toyota has no recommended change interval on the HO2 sensors.

When the HO2 sensor is at operating temperature, the voltage output of the sensors is 0.45V at the correct Fuel/Air ratio. Higher voltage than this indicates a rich mixture. The higher, the richer. Lower voltage is leaner. The output voltage of the HO2 sensors should oscillate around 0.5 V while operating normally.

The comparison made by the ECM to report a bad cat converter is not relative voltages (since they constantly change owing to the design of the HO2 sensor), but waveform frequencies. The frequency and peak voltage of the upstream [bank 1 sensor 1] sensor should be higher than the frequency and peak voltage of the downstream [bank 1 sensor 2] sensor. If the frequency is pretty much the same, then the catalyst performance has deteriorated.

The HO2 sensors are tested by measuring their resistance. The resistance between terminals +B and HT should be 11-16 ohms cold, or 23-32 ohms at operating temperature.

You should be able to measure the frequency of the waveform from both HO2 sensors (thus checking catalyst function) by connecting a voltmeter (0-1 V scale) or oscilloscope to terminals OX1 [bank 1 sensor 1], OXS [bank 1 sensor 2], and E1 of the ECM connector. Check the terminal voltages/waveforms while running at 2500-3000 rpm. The engine should be first warmed up at idle until hot, and then heated by running it at 2500-3000 rpms for 3 min.

Note: This does not apply to an engine with an Air/Fuel ratio sensor instead of an HO2 sensor.