O2 sensor replacement

[Bluevitz-rs]

Has anyone replaced their old o2 sensor or AFR in the yaris and noticed a boost in MPGs?

My car has been running really rich, turning the exhaust tips black and a lot of gurgle and popping between shift indicating such. I did a trip to Florida and back from the Toronto area and only got around 32 MPG US. Obviously it was all hwy/freeway driving at an average of about 70mph. Changed out my aging standard plugs for some new NGK iridium plug and it didn't really change much other than it just runs a bit smoother.

I'm going to pull the injectors to see if one is maybe clogged or dirty and the ECU is tying to compensate, because the last time I had a tech steam tool connected, I noticed the LTFT (long term fuel trim) was quite high into the plus side, I think almost to the max the ECU will compensate. My millage hasn't changed from the depths of our frigid winter temps to now.

[fnkngrv]

When I changed mine I notice a slight increase by a couple mpg prior to moving to my EMS.

If you have any genuine issues with your stock injectors themselves give me a shout as I have the 4 of mine that were pulled when I went boosted. Heck, I would most likely just ship you 1 for the cost of shipping.

[Bluevitz-rs]

Just pulled and cleaned them with carb cleaner. Swapped them around so now they're 4-3-2-1 instead of 1-2-3-4 and no.3 is leaking like a SOB spraying everywhere. Duck my life! Duck you autocorrect!

Going to phone around now and see if anyone carries them. Luckily I have the bike but it's cold and threatening rain.

[WeeYari]

Originally Posted by Bluevitz-rs

no.3 is leaking like a SOB spraying everywhere.

Hopefully an obvious question, but did you pull #3 out again and try to re-seat it? Had it happen to me once, and re-seating worked.

[fnkngrv]

Like I said I actually have 2 sets.

sent from my m-o-b-i-l-e

[Bluevitz-rs]

No the O-ring must have ripped. I got a new set and going to change them all. Not taking any chances. $1.76


Sent from my iPod Touch

[Bluevitz-rs]

How much was your sensor? I can get a factory one for about $135 or a NTK one for $120. Both plus tax.

Also, I know I have a small crack in my exhaust just before the resonator under the hanger bracing so it's inaccessible. But I can't see that kill my mileage by almost 20%.


Sent from my iPod Touch

[fnkngrv]

I did Bosch from local auto parts and paid 70

sent from my m-o-b-i-l-e

[Bluevitz-rs]

Ok. Fuel injectors done. No more leaks.

Next will be a nice day to pull the exhaust off the car to repair the crack and hit the o2 sensor with the torch so it comes out without issue.


Sent from my iPod Touch

[IllusionX]

I only wish i had more time to work on my car!

[quicksilver7]

Hey guys, 2 questions. How do you check if the fuel injectors are bad or due for a change? How do you check the O2 sensor?

Cheers!

[Bluevitz-rs]

Well you can't really, other than your fuel economy starts to decline like mine has.

I've always had a misfire code come up on cyl.2 in pending codes list. So I'm finally trying to eliminate all other possibilities. Swap coils around, and now injectors. So if I keep getting it it's now down to the valve train.


Sent from my iPod Touch

[Bluevitz-rs]

So I had a friend hook up his Techstream Computer from Toyota and at idle, my LTFT is 20-32%!! But as soon as the throttle is cracked it goes down to 4-7%. So the O2 sensor is working fine. On the graph it's flutuating up and down as it normally should, so he said there has to be a vacuum leak somewhere.

The head was re-done by the dealer early in the cars life due to an over-rev to about 8700rpm. The top of 3rd passing two gravel trucks on a two lane road back to 2nd will tend to do bad things. Anyway, they replaced 3 or 4 valves and redid the shimming accordingly, but I've always had a slight misfire on cyl 2 as I mentioned, and plug 2 always comes out looking lean with white dust on the ground. So my next corse will be to do a compression test and leak down test to determine if there is a leak. I'm hoping I don't have to do anything major.

I'll also pull the intake mani off and make sure it's sealed up to the head 100%.

[fnkngrv]

I have my head with valvetrain in case you see that you have problems. Best of luck.

sent from my m-o-b-i-l-e

[Bluevitz-rs]

I've checked for vacuum leaks with a propane torch (not lit of course) and couldn't find any leaks.

My millage has returned to normal, so my only guess was that because I was running 5W-20 oil, my engine was actually burning oil on the really long distance trip. I'll be running thicker oil from now on.

My only issue is still the possible vacuum leak. It seams to be getting worse as my car's idle is very rough. Without a scope I can only guess I might have a leaking valve or something. I still want to perform a leak down test but can't find anywhere that rents them. I might just try a compression tester, or make one out of an old spark plug to fill each cylinder with compressed air and listen for leaks on the intake and exhaust sides.

[Bluevitz-rs]

So since my last post I've swapped the injectors and coils around to see if the problem with cylinder 2 follows. Went 1234 -> 4321.

Pulled more codes from the car again. P0300, P0302 Pending and P0138.

P0300 is a random misfire code, 302 is specifically cylinder 2. and P0138 is O2 Sensor 2 Bank 1 Voltage too high, probably brought on by the misfire.

So I'm finally going to get that compression tester and see what's going on.

Years and years ago my air filter fell off for an unknown amount of time. I finally found out when something jammed in the throttle body causing the car to idle at 3500 rpm coming off the highway. So I'm assuming there's some internal damage of some kind to the valve seats or cylinder walls.

If that's the case, I'll be saving up to build a custom turbo setup with fuel economy in mind with a used rebuilt head and the brand new short block I've had sitting in my shed for years.

[Bluevitz-rs]

Update.

My milage from recent tanks was getting very bad compared to what should be normal and from what the car used to get years ago.

Had a different friend hook up his techstream computer and did an active test on fuel enrichment while looking at the O2 sensor voltage and determined that the sensor had gotten lazy to the point of not reading a rich mixture any more. It was also very slow to react. Voltage was only reading between 0.10V and 0.49V. (Lower voltage meaning lean and higher voltage meaning rich) So I replaced the sensor with brand new NTK (same as factory OE) sensor. Voltage now reads between 0.02V and 0.93V and quite quickly.

The temp has been hovering around the freezing mark here and I've now gotten 100 more KM out of the same amount of fuel from my last tank. That's an insane improvement.

I had hoped that was all there was to it, but alas, the rough idle remains and sadly my check engine light came back on again while idling. I have yet to check the codes. More than likely P0300 the way it was shaking on idle.

[Jcp123]

If it was running rich, is it possible that the plugs are fouled? I don't see where you have pulled the plugs for a look. Also, not sure what the tech stream is capable of, can it run an injector balance test?