Hey everyone,

had just got my girlfriend a 99 Corolla, and from a quick estimation
the mileage isn't that great at all, she claims it got like 110 miles
on 3/4 tank of fuel (thought the trip/odometer HAS to be incorrect)-
as the car runs great, only goes through a teeny bit of oil here and
there. Just put in a new set of original Denso plugs, Denso wires,
air filter, and PCV valve (have the OE upstream senor on order too).

Plugs looked fine, nicely "aged", no fouling, no oil on/in them.......

Car really does run pretty smooth....... trying to think of what else
to try for improving mileage (besides tire pressure, etc. etc.)

Can a bad/borderline upstream O2 sensor, cause mileage to be just HORRIBLE- despite the car running great 100% of the time??!!

I'm going to also go in and give the throttle body a good cleaning
when installing the O2 sensor.

Thanks for the cross-post in a sense folks (being a Corolla and not a
Camry that is).

Sincerely, Bob.

 

Might do your own test.

What did the spark plug electrodes look like? Black, gray, white? All the same condition?

Clean MAF sensor. Use a cleaner safe for plastics.

Any chance the emissions converter is plugged?

A bad 02 sensor can cause low MPG.

Check the ETC sensor. This provides computer with coolant temp signal.

Vacuum leaks.

EPA MPG is 31 city/28 hwy.

 

I will check into these things, thanks Joey!

The plugs looked fine, the tips were not black,
or oily or anything like that. They were well worn,
but with white tips/electrodes- if anything.... maybe
it was running a tad lean??!

And all 4 of them were consistent/looked like this.

IF the emissions converted was plugged, wouldn't
the engine not be running as good and smooth as
it is..... there is a decent amount of exhaust "pressure"
coming out of the tailpipe! The engine runs very smooth.

I will check for vacuum leaks also, I'll spray a bit of carb
cleaner or similar around all the areas where there could
be any of these leaks too- thanks!!

I'll do what I can, including putting in the new O2 sensor
soon, and will get back with updates once we track the
mileage a bit more after some of these little fixes!!

Sincerely, thanks again and again list!!!!!!
Bob.

 

If the engine has normal power and accel the converter should be OK.

Post back with your finds.

 

Here is what I would do to avoid just throwing money at it:

1. Login to https://techinfo.toyota.com/techInfo...pmanager/t3/ti. It will cost you $15 for a 2 day sub. Pull up all sheets on the main ignition, powertrain, air/exhaust, and fuel components (like ECT, MAF, etc.), and Print the pages as a PDF - that way you have them electronically.
2. Write down all the test parameters for these sensors (as in, for my Camry the MAF should provide a reading of 0.5 g/s when the key is in the ON position)
3. Head to AutoZone. They perform scanner services for free. They use the Actron 9580A which will test most of these components. be sure to get your proper O2 sensor output values, as you can watch them graph on their scanner. Now, the AZ guy may not know how to use the tool (dudes at my local AZ did not know, they thought all this $200+ tool did was check CELs. I had to show them what it could do), so you may have to coach them.
4. Write down the values the scanner gives you back. Just be aware of the units. The default for MAF on that scanner is LBS/M, whereas the parameters Toyota is looking at is g/s, so just convert. If .5 g/s, then the target LBS/M is .066 or lower. As an example.

This is a $15 way to basically get a diag on your vehicle. Not as good as a pro shop will give, but a hell of a lot better than head scratching. All the stuff you have done is great, but this will help pinpoint something that may be wrong.

 

Hey DIYDad,

sounds good, I will check into the techinfo.com thing- thanx!
For 15$- well worth the info I can keep on .pdf/hard copy!!

I'll download all the papers you suggested for my girls 99 Corolla-
and the same info for my 98 Camry (for future reference)!!!!

As for the common items relating to performance/economy, I
don't mind changing them out, as in the upstream O2 sensor,
plugs, wires..... already did the plugs and wires, they were WELL
worn. So with other items related seemingly original (maybe)- or
just being in service for a long time....... no problem here for me
to replace them!!

I was a mechanic for awhile, back a few more than a few years ago...lol!


So I try and do most all things myself, if I can?! Will check all the parameters
with the code reader too.

Thanks again and again, sincerely Bob.

98 Camry 4cyl.
(previous)
95 Tercel.
99 Voyager
77 Fury Wagon
72 New Yorker
70 Superbee
67 Newport

 

You bet. Another great option there is, if you buy the Mongoose cable, a $50 sub for 2 days gives you access to Techstream. Get the cable first from wherever, get a laptop ready, and then pay the sub. You get a link to the software, and DL it, then go to town. That will be my next adventure when I need to do this again.

 

Techstream cable 25 bucks, Ver10
software DL: http://down.obd365.com/toyota-techstream-10.00.028.zip

 

I bought version 9.x something or other and have been using that. Cost me the same $25, and has been pretty good for my Toyota's. Doesn't always work, sometimes you have to re-start the program, and I have had it just dump out on me a few times. I did load it on an old Dell laptop running XP rather than fight it into submission on an x64 based OS.

 

Hey again folks,

been a LONG time since I've even signed on, funny how life,
can get in the way of life sometimes.........

The last time I signed on, there were several people who had
a bunch of great ideas to help with checking on the mileage!

Well, seeing as my priorities had changed at that point, all
I could do was try some Lucas upper cylinder lubricant/fuel
injector cleaner, as at that point in time I wasn't doing any
car work- for a long time.......................!

AND, I had replaced the coolant temp sensor as well! The
mileage came right back up into the low end of what the car
should be getting! Then a couple/few months of using the
Lucas product, my girlfriends mileage eventually came up
more and more!! The car doesn't get 31 MPG in the city
as when it was new, but the mileage in the city is up in the
high 20's for MPG. Highway mileage is up there too!!

I just wanted to take the time, finally- to thank all of you
out there for the opinions/tips/tricks/etc...!!!!

I gotta say, the couple gallons of the Lucas were WELL
worth it, does anyone else here have similar stories
about this old-school product- as I'd LOVE to hear them!

Sincerely, Bob.