Slowly falling gas mileage - Toyota Nation Forum : Toyota Car and Truck Forums
Highlander 1st Generation (2001-2007) Forum dedicated to the discussion of 1st generation Toyota Highlanders.

Reply
 
LinkBack Thread Tools Display Modes
post #1 of 16 Old 04-07-2019, 07:17 AM Thread Starter
New TN User
 
Join Date: Feb 2019
Posts: 18
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Thanks: 0
Thanked 0 Times in 0 Posts
iTrader Score: 0 reviews
(Thread Starter)
Slowly falling gas mileage

217K miles on 06 V6 4wd. Well maintained, engine and trans run great, brakes are well maintained. In fact, overall the vehicle is in great shape considering the duty it's pulled, so I'm inclined to put a little effort into helping it up to really high miles.

Gas mileage seems to be falling, very slowly. About 10% poorer last year or two in gentle driving, worse than that if I am more aggressive on the pedal. The two upstream O2 sensors are original, and in my mind becoming suspect simply due to age. One downstream sensor changed out about a month ago (P0158, high voltage), no other codes.

I hate to change out $112 parts in the blind. Is there a way to test the A/F system using Torque or Techstream? I have not yet used either of these... will have Torque running in a day or two, wouldn't mind getting some input on Techstream. Guessing the good deals to be had on ebay are all Chinese pirates? Malware issues, anyone?

Anyhow, if anyone has a minute, throw me a bone please, it won't go wasted. I'm a process engineer, live and breathe control systems for things other than cars, did a bunch of amateur tuning and logging on 3 different WRXs a few years ago with great success. TIA.
Ralph Spoilsport is offline  
Sponsored Links
Advertisement
 
post #2 of 16 Old 04-07-2019, 11:02 AM
cj1
Senior TN Member
 
Join Date: Jan 2014
Location: calif
Posts: 1,997
Mentioned: 6 Post(s)
Tagged: 1 Thread(s)
Quoted: 346 Post(s)
Thanks: 9
Thanked 187 Times in 184 Posts
iTrader Score: 0 reviews
A/F system meant to keep fuel trims LT + ST close to zero up/down the RPM range.

The more positive the trims the more fuel is being added.
If your less then +10 probably best you can do considering the high mileage.
The torque app is sufficient for checking fuel trims/A/F sensor response.



Monitor the A/F sensor for full range with some quick snap throttles.
It should vary from 3.3v( normal idle reading) up to 4v/ back down to 2.5 and up to settle at 3.3.
cj1 is offline  
post #3 of 16 Old 04-08-2019, 10:34 AM Thread Starter
New TN User
 
Join Date: Feb 2019
Posts: 18
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Thanks: 0
Thanked 0 Times in 0 Posts
iTrader Score: 0 reviews
(Thread Starter)
Thanks...

I got Torque pro up and running... fuel trims are all +/- 3%, AFR sensors behaving properly (I spent a little time on google & youtube learning about those), downstream sensors behaving properly. Nice to be able to confirm all that. WOT highway performance is good, car runs just like it always has, just seems to hit me harder at the pump. Next up I'll run the tank dry and switch gas stations (I've been favoring the cut rate unbranded station).
Ralph Spoilsport is offline  
Sponsored Links
Advertisement
 
post #4 of 16 Old 04-08-2019, 11:56 AM
Do you feel lucky?
 
TrailDust's Avatar
 
Join Date: Mar 2008
Location: Kalifornication
Posts: 33,737
Mentioned: 83 Post(s)
Tagged: 1 Thread(s)
Quoted: 7219 Post(s)
Thanks: 3,997
Thanked 8,418 Times in 5,928 Posts
Lifetime Supreme Member
iTrader Score: 1 reviews
When was the last time you changed your spark plugs? Also, I agree, change the top tier gas supplier, but make sure you're not filling up at Costco.



-------------------------


2008 Highlander Base 4WD
2002 Avalon XL
1987 Suzuki Samurai 4X4 - Treading where no Jeep can follow....
TrailDust is offline  
post #5 of 16 Old 04-08-2019, 01:49 PM Thread Starter
New TN User
 
Join Date: Feb 2019
Posts: 18
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Thanks: 0
Thanked 0 Times in 0 Posts
iTrader Score: 0 reviews
(Thread Starter)
Quote:
Originally Posted by TrailDust View Post
When was the last time you changed your spark plugs? Also, I agree, change the top tier gas supplier, but make sure you're not filling up at Costco.
Plugs are top quality iridium, 95k miles.

When I changed out the OEM iridium plugs at 122K, they looked like they had been driven around the block. I really wondered why I bothered. Based on that experience, I'd expect plugs to be the least of our problems -- is there evidence to the contrary?

When I saw the AFR/O2 readings performing perfectly, next thought was "plugged cat(s)". So my next move (this morning) was to take the long highway route to work, get everything good & hot, give it the boot on a long uphill following a freeway onramp (this car gets driven very gently for the most part although it does a fair amount of tow duty in the Summer). Performance was 100% satisfactory, as new, no smoke. So I think the evidence is fuel, ignition and exhaust systems are all okay (and that's pretty sweet on a > 200K vehicle -- the only bits of those systems so far replaced are 1 set of plugs, 1 downstream O2 sensor (a month ago), pinch bolts ahead of rear catalyst).

Oil consumption is nil. Less than 1/2 qt in 9000 miles on 0w-30 Mobil 1 AFE.

Ashamed I didn't think of this sooner: I did change tires last year. I had Michelin Defender. The Defenders are low rolling resistance for sure. That's about the only really good thing about them, so I replaced with Hankook Kinergy (at about 1/2 the price). There appear to be multiple versions of the Kinergy. Mine are USA made and have a treadwear number of 680. No idea on rolling resistance comparison, but obviously it matters. I'd believe 1 mpg due to tires and 1 mpg due to gas, so perhaps the car is all good. Shrug.
Ralph Spoilsport is offline  
post #6 of 16 Old 04-08-2019, 04:31 PM
Official TN Member
 
Join Date: Feb 2014
Posts: 103
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 22 Post(s)
Thanks: 4
Thanked 15 Times in 12 Posts
iTrader Score: 0 reviews
Couple of other items that can decrease mileage:
  • wheel alignment
  • dirty air filter
  • bad fuel injectors
When was the last time you changed the PCV valve?

2002 Nissan Sentra GXE 5SPD Sold
2003 Honda S2000 Sold
2001 Highlander V6 AWD Sold
2014 Porsche Cayenne V6
2018 Honda Civic Type R

9009RPM is offline  
post #7 of 16 Old 04-08-2019, 05:37 PM Thread Starter
New TN User
 
Join Date: Feb 2019
Posts: 18
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Thanks: 0
Thanked 0 Times in 0 Posts
iTrader Score: 0 reviews
(Thread Starter)
Quote:
Originally Posted by 9009RPM View Post
Couple of other items that can decrease mileage:
  • wheel alignment
  • dirty air filter
  • bad fuel injectors
When was the last time you changed the PCV valve?
Wheel alignment is good.
Air Filter changed out roughly every 20K, last time about a month ago (Dry days in Winter here come with a big dirt load).
PCV changed last Fall (second time). About 100K on this one, like the first one, it came out of the car working like new.
How would I test fuel injectors? I'll google that.
Ralph Spoilsport is offline  
post #8 of 16 Old 04-10-2019, 09:48 AM Thread Starter
New TN User
 
Join Date: Feb 2019
Posts: 18
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Thanks: 0
Thanked 0 Times in 0 Posts
iTrader Score: 0 reviews
(Thread Starter)
Figured it out this morning. Or at least I think I figured out the last bit of the puzzle.

I replaced the LR wheel bearing several months ago and took the opportunity to replace the brake backing plate. NH has vehicle inspections, so I have to maintain the fiction of a usable e-brake although pretty much everyone understands that the e-brake on a Highlander is just for show (at best). It is by far the poorest engineered system on the car. Criminally *****y. Anyhow, I was pleased to find that there was finally an aftermarket backing plate available. The problem is, I now think something is very slightly out of whack in the manufacturing tolerances. I think the post at the top that locates the brake shoes is very slightly off proper location w.r.t. the axle.

I thought I had it, but I "hyper miled" the last several miles to work this morning, parked the car, checked the brakes by hand and darned if the left rear rotor hat is warm when it shouldn't be. I've already screwed with that e-brake a couple of times, thought I finally had it sorted out. What a complete pisser.

My plan is to yank the rotor, spray paint the shoes, put it back together and spin the wheel enough to show where things are rubbing (guess is the top of the brake shoe assembly) then grind the shoes down where it's rubbing. If that doesn't work, I rip the ef'fing ebrakes out until due for next inspection.
Ralph Spoilsport is offline  
post #9 of 16 Old 04-11-2019, 08:05 PM Thread Starter
New TN User
 
Join Date: Feb 2019
Posts: 18
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Thanks: 0
Thanked 0 Times in 0 Posts
iTrader Score: 0 reviews
(Thread Starter)
...as promised, chalked the shoes, spun the drum, offending bit is clearly top of front shoe, ground down a bit with coarse sandpaper and a block, tightened up the return springs, test ran it on the jack, seemed good. Drove it... hell and tarnation, it's still getting warm. Back home, back on the jack, did the e-brake delete both sides, cursing Toyota engineering the whole time. I'd forgotten that I'd have to loosen the bearing housing in order to get the straight retaining pin out (special curses there). Mission accomplished, short test drive, car feels better, I can tell that drag is way down. Fresh tank of Sunoco 87 (we should be on Summer gas now), I expect to see better numbers.
Ralph Spoilsport is offline  
post #10 of 16 Old 04-12-2019, 04:28 PM
Official TN Member
 
Join Date: Apr 2017
Posts: 182
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 26 Post(s)
Thanks: 0
Thanked 4 Times in 4 Posts
iTrader Score: 0 reviews
I have an 04 v6 awd 256,000 miles. It's getting slightly worse mileage than it used to. My suspects are: cat, af sensors, and vvt solenoid valves. I've been wondering about the vvt system because when accelerating hard the car will suddenly take off at a certain rpm. So if it's not working properly until higher rpm, maybe that's my culprit and part of your problem too.
Mgeorge is offline  
post #11 of 16 Old 04-12-2019, 06:30 PM Thread Starter
New TN User
 
Join Date: Feb 2019
Posts: 18
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Thanks: 0
Thanked 0 Times in 0 Posts
iTrader Score: 0 reviews
(Thread Starter)
Quote:
Originally Posted by Mgeorge View Post
I have an 04 v6 awd 256,000 miles. It's getting slightly worse mileage than it used to. My suspects are: cat, af sensors, and vvt solenoid valves. I've been wondering about the vvt system because when accelerating hard the car will suddenly take off at a certain rpm. So if it's not working properly until higher rpm, maybe that's my culprit and part of your problem too.
I have the 3MZ-fe engine, yours is the 1MZ, so there are differences. However, both engines have a variable length intake runner system. On the 3MZ, you can feel the switch, there's a distinct bump in torque at around 4K rpm (WOT). My car has always done this, it's completely normal. I think this is probably what you experience (although your system is different).

If your VVT system was not keeping up, it would throw OBD error codes.

How do you keep your e-brake from dragging :-)?
Ralph Spoilsport is offline  
post #12 of 16 Old 04-13-2019, 10:27 AM
Official TN Member
 
Join Date: Apr 2017
Posts: 182
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 26 Post(s)
Thanks: 0
Thanked 4 Times in 4 Posts
iTrader Score: 0 reviews
I do have a 3mz fe engine, I think the 1mz fe is the 4 cylinder. Good to know that bump in accelleration is normal, thanks! I had read some posts that people had some improvement changing those solenoid valves even though they appeared fine... As far as the parking brake, I had some trouble with it dragging a couple of years ago and it was due to a crack at the base of the parking brake cable right where it goes through the backing plate. It caused the cable to rust a bit and not fully release after it was applied. sometime after that I did a brake job and new rotors and the brake was dragging so I just backed the adjustment off until it didn't drag, but I went a bit too far and haven't had a working parking brake ever since.
Mgeorge is offline  
post #13 of 16 Old 04-14-2019, 02:42 PM
Official TN Member
 
Hayabusafalcon's Avatar
 
Join Date: Sep 2012
Location: Michigan (snow belt)
Posts: 461
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 60 Post(s)
Thanks: 3
Thanked 59 Times in 48 Posts
iTrader Score: 0 reviews
Cool There's and aftermarket backing plate?

Ralph Spoilsport....where did you get the aftermarket backing plate? Haya....


or anyone.......


Thanks!

aka Slick from Ada
Hayabusafalcon is offline  
post #14 of 16 Old 04-14-2019, 09:04 PM Thread Starter
New TN User
 
Join Date: Feb 2019
Posts: 18
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Thanks: 0
Thanked 0 Times in 0 Posts
iTrader Score: 0 reviews
(Thread Starter)
Quote:
Originally Posted by Hayabusafalcon View Post
Ralph Spoilsport....where did you get the aftermarket backing plate? Haya....


or anyone.......


Thanks!
Dorman. They come in pairs only. Ebay.

Quality is excellent... although wondering about dimensional tolerances as previously noted. On further reflection I think the backing plate is probably okay and my problem was instead crummy brake shoes and hardware. I think I paid $120 for the pair. Have an unused right rear available if someone wants to paypal me $60 plus shipping.
Ralph Spoilsport is offline  
post #15 of 16 Old 04-15-2019, 06:26 AM
Official TN Member
 
Hayabusafalcon's Avatar
 
Join Date: Sep 2012
Location: Michigan (snow belt)
Posts: 461
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 60 Post(s)
Thanks: 3
Thanked 59 Times in 48 Posts
iTrader Score: 0 reviews
Cool Ok but what about 2003 HL?

Quote:
Originally Posted by Ralph Spoilsport View Post
Dorman. They come in pairs only. Ebay.

Quality is excellent... although wondering about dimensional tolerances as previously noted. On further reflection I think the backing plate is probably okay and my problem was instead crummy brake shoes and hardware. I think I paid $120 for the pair. Have an unused right rear available if someone wants to paypal me $60 plus shipping.
Ralph-Anybody....
Does anybody know if the ones shown for 2004-2007 will fit the 2003?

aka Slick from Ada
Hayabusafalcon is offline  
Sponsored Links
Advertisement
 
Reply

  Toyota Nation Forum : Toyota Car and Truck Forums > Toyota Truck, SUV and Van Forums > Highlander Forum > Highlander 1st Generation (2001-2007)

Bookmarks

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome