Sudden drop of MPG

[medfordhotrodguy]

Well just got back from driving it for about 1100 miles. Best mpg I got was 14.4. I called my b.i.l. who works as a manager at O'Reilly's and had him order me in 4 new calipers and performance friction front pads and Wagner rear pads. I'll be putting them on probably next weekend as the shop has been extremely busy lately. Been working 13-14 hrs/day for the last 7 weeks. I did compress every piston in every caliper before I left on my trip, and not 1 of them showed any resistance. I'm just going to rule out the brake issue.

 

[Bob J]

Well just got back from driving it for about 1100 miles. Best mpg I got was 14.4. I called my b.i.l. who works as a manager at O'Reilly's and had him order me in 4 new calipers and performance friction front pads and Wagner rear pads. I'll be putting them on probably next weekend as the shop has been extremely busy lately. Been working 13-14 hrs/day for the last 7 weeks. I did compress every piston in every caliper before I left on my trip, and not 1 of them showed any resistance. I'm just going to rule out the brake issue.

Wear pattern on your pads is a pretty good tell for caliper issues as well.... When I replaced my rear calipers one wheel had a pad almost completely worn down and the other only about 50%.... That problem was guide pins and not the caliper itself but went ahead and changed anyway....

 

[medfordhotrodguy]

I pulled all the tires off Saturday evening. All 8 pads were worn evenly. Being that I am an A.S.E. Master certified tech I do know what to look for. This truck doesn't pulse when braking. It doesn't pull in the slightest when braking or while driving at any speed. There is no discoloration of any of the rotors. My IR thermometer walked off a couple weeks ago, so I have to get another 1 before I can check surface temps again. I have almost zero bearing noise on the scope at all 4 corners. Front bearing deflection is less than .005".
I honestly believe it has more to do with the electronics of the vehicle, then a mechanical issue. The fact that the on board computer is off by 4.5mpg over actual mpg. When we bought it 3+ yrs ago, it was off only by ~.3mpg. All of this happened after the recall reflash of the ecu.

 

[medfordhotrodguy]

Update

Ok, so Friday evening I dove into the runner head first. I pulled both drivelines and sent them over to a friend to get rebuilt and balanced. I pulled both front cv's and replaced them with new ones. Pulled both front hub assemblies and replaced them with new ones. Pulled all calipers. (now we bought this from the original owners who had every record for it. It has 116,400 miles now and had ORIGINAL BRAKES.) I was able to compress EVERY piston, front and rear, by HAND. Nothing was seized. I had no uneven pad wear. I went ahead and changed out all calipers and pads. Turned all 4 rotors. I also backed off the parking brake a couple clicks just to rule out it was dragging. I changed the fluid in both diffs with some Shell synthetic.

After it was all put back together: I filled it up, reset the trip computer and the average mpg calculator. On Saturday evening we drove up to South Lake Tahoe, about 200 miles round trip from the house, and filled up when we got back. Got a whopping 13.7mpg!!!! We drove the posted speed limit. I was even on and off the gas. We have done this trip dozens of time since purchasing the runner and this is the worst mpg yet. The first year and a half of owning it, we always got better than 18mpg.

I have now run out of ideas. It has to be something in the ecu. I have shearched and read all over. I have found some cases of mpg drop after the gas peddel recall, but Toyota is saying it "never happens".

Anymore ideas guy?
I'm all ears. I really don't want to sell this, but it's getting expensive to just start it up.

 

[Greydog]

Can you test O2 sensor operation and tailpipe emissions? If its running rich, it should show either in the O2 data or performance or the tailpipe output.

Speaking of it, a failing O2 will also drive down the MPG somewhat, right ?

 

[medfordhotrodguy]

I just did my year ly smog test 2 weeks ago, it barely moved to needle. I was going to data log our trip on Saturday, but my scanner was logging a customer's car for the weekend.
I don't think we will be driving it much over the next month as my wife is due August 1. If we do go anywhere we will be driving my Legacy.
I do think sometime soon I'll just drive it around the neighborhood while logging it to see if there is anything there that needs to be looked at closer.

 

[Pasha]

Wondering if you still have your v8 4Runner and if you fixed the poor mpg issue. I owned my 2006 v8 4Runner for 2 years now. Had my timing belt replaced a year ago with waterpump, sparkplugs, front rotors and brakes and the whole nine. Just recently I went from averaging 18mpg down to 15 mpg. This happend on the during our vacation trip to Florida in May. The first time I noticed I figured it was just a poor fillup and thought the next tank will go back to normal. Second tank, same thing. Third tank also. Nothing changed with my driving, and most of it was hwy too so I actually expected 19-20mpg and not 15mpg. Ran seafoam as it usually helped on my previous vehicles but nothing on this one. Month later, I had transmission flushed and had fuel injectors cleaned thinking that might help, nothing changed though. I also, had the recall reset done while at the Toyota dealership and that didnt changed anything either. Not sure what could bring the mpg back where is should be. I was also, thinking of addressing the cracked manifold that seems to be an issue on the 4.7 v8 engines thinking that the o2 sensor isn't reading it correctly due to the gasses escaping through the cracked manifold but I read you've already replaced yours and that didn't help. I'm at a loss as to what can fix this. I'm going to replace my sparkplugs, if that doesn't fix it, I'm selling it..

 

[rdesouza74]

I've recently noticed my 07 4runner 4.7 v8 SR5 on the last trip I made that normally on a full tank it would show on the gas mileage trip on center console, from being full like 345 miles to E. on my way back from that trip it dropped to 298 on a full tank. I've done 3 full tanks so far, and they're all under that 340 range. last week it actually went to 309 but that was it! only thing I did to it is put new tires on it 265-70-17 wheels instead of the old 16in, but that was done before the trip. tires are all matching pressure, I even put a new gas cap on it too. any ideas are greatly appreciated!!! thanks in advance, also no lights or codes are on either

 

[AuSeeker]

I've recently noticed my 07 4runner 4.7 v8 SR5 on the last trip I made that normally on a full tank it would show on the gas mileage trip on center console, from being full like 345 miles to E. on my way back from that trip it dropped to 298 on a full tank. I've done 3 full tanks so far, and they're all under that 340 range. last week it actually went to 309 but that was it! only thing I did to it is put new tires on it 265-70-17 wheels instead of the old 16in, but that was done before the trip. tires are all matching pressure, I even put a new gas cap on it too. any ideas are greatly appreciated!!! thanks in advance, also no lights or codes are on either

I'm assuming your 16" tires were 265-70-16, which is the OEM 16" tire size for a 2007 4Runner, now you have 265-70-17s, which isn't the OEM 17" tire size for a 2007 4Runner, the correct 17" size is a 265-65-17 and is overall the same diameter/height, circumference, etc. as the OEM 16" tires and with a 265-65-17 you would still see the same mileage as you did with the 16" tires.

Now that you have the 265-70-17 tires they are bigger than the OEM 16" tires, the OEM 16" tires are 30.6" in diameter/height and have a circumference of 96.1" and 659 revolutions per mile, the 265-70-17 tires are 31.6" in diameter/height and have a circumference of 99.2" and 638 revolutions per mile, so you are actually going further for every mile shown on your odometer than the 16" tires were going, so you're most likely getting the same mileage as before it's just that now your speedometer and odometer are now off and not the correct mileage, and you are going faster then the speedometer is indicating.

The above mentioned specs are for the same brand of tires and in this case it a speculative brand just for comparison, the specs can be sightly different for these same size when the tires are of different brands.

To know for certain the actual specs you would need to research the specs of the actual tires you have now and the tires you used to have, and the number scan be +/- of what I posted above.

To know for sure what mileage you're getting now you need to use a GPS that shows MPH, but more so the miles driven, etc. and track your mileage and then do the math

The following links is where I got the above specs.

OEM 16" and 17" tire specs, click on the sizes to the right of the tire for the sizes and specs.

2007 Toyota 4Runner 2wd SR5 Tires

Specs on the size you are running now.

265/70R17 Tires

 

[Bluesky 07]

FWIW, the console miles remaining indicator is meaningless. I’ve tracked every fill-up for 3+ years using actual miles traveled per the trip odometer divided by gallons to fill. My average MPG over that time is 17.2. Multiply that by the 23.5 gallon fuel capacity and the tank should run dry at ~400 miles. I’ve run the counter down past zero and ended up putting in only 20 gallons or so. Now I go by the trip odometer and fill up by around 360-370 miles just to keep a buffer.

Of course, YMMV. Literally.