Low MPG after Service

I have a 2019 ORP that just went in for its 50k fluids and alt belt, and I did a new MAF (I broke the old one while cleaning), Throttle body clean, new PCV, and new K&N Filter. Before all this I was seeing 16-18 MPG, now Im seeing 13-14. I did have to wait while the new MAF came in and drove ~150-200 miles on the broken MAF which did mess with the Fuel trim, but Ive driven 350-400 miles on the new one and its barely gone up even though Ive been driving like a grandma. The MAF is reading decent values in my OBDII, and on highway light cruising I see 20+MPG. Done a few resets with disconnecting battery for 10+ min. Also no mods besides bike hitch rack and Falken Wildpeaks 265

Anyone have any thoughts on the issue? Just more miles to retrain the ECU?

 

That’s a lot of work for 50k.

You needed a new alternator belt?

 

Yeah, I moved and tried a different dealership and they said it needed to be replaced because it was "glazed". I dont fully trust them though, they wanted like $1800 for all the above repairs and I couldnt pay that much so I had them do the stuff I cant do in my apartment parking lot, which was all fluids and the belt.

 

How does it run? Loosing 3-4 MPG after a service doesnt seem right. You may have an air leak somewhere on the boot causing it to run richer than normal... Or possibly got a bad PCV (which why did you replace it at 50k anyway?) or a crappy MAF sensor, or possibly over oiled the air filter (if you oiled it yourself).

 

By disconnecting the battery, it resets the ECU to factory settings. It will take a while for it to relearn. If your fuel economy still sucks after a few tanks of gas then I would be concerned. But, it will probably suck for a few hundred miles at least.

 

Runs seemingly fine, on my current tank at over 150 miles I’m up to 15mpg with a mix of city/highway. The dealer recommended PCV (also I did MAF replacement and got bad gas mileage before PCV), MAF replacement was brand new from toyota, and brand new air filter. I can double check the air box to throttle body connection, but seemed to be all the way to the stops with the clamp tightened down.

It’s been about 300 miles since the new MAF and ECU reset so I’ll give it the rest of this tank and see if it gets better

 

Unfortunate that you went to a dealer that lied to you.
No need to clean a MAF at your mileage....my buddy also has a 2016 with 170K and it's never been touched.

 

I’m curious as to what fluids were replaced. The only fluids I’ve had replaced besides oil is trans fluid at 90k miles.

 

You don't do a diff service?

 

Not at 50k miles. But I was just curious what he’s referring to.

 

I think every 50k is proper, but Toyota is so vague.....I did mine at 60k and will do again at 100k with a slew of other things.

 

I settled on a 100k interval for that years ago. Longer than recommended (I think) but I’ve had no problems with it.

 

I do my diffs every 30, but I do wheel hard usually twice a week.

 

Me too but I just did my gearboxes at 24k which is early but it fit my schedule.

Transmission fluid service is recommended at 60k.

 

Actually, it says 60k if "Driving while towing, using a car-top carrier, or heavy vehicle loading." It says it again at 120k miles. I can't find a 'normal driving' interval, but I'm sure one exists. Looking at the 2019 4Runner Warranty and Maintenance Guide.

 

Unless you are purely commuting in an empty vehicle in a 54 degree standard climate, you probably wouldn't fall under normal.

 

This is why I do 5K oil changes.

 

Maybe. It's just interesting that they don't call out anything other than severe conditions (I drive under light conditions). Maybe it's this:

2002 - WS Fluid[edit]
Toyota WS Fluid

In 2002, Toyota releases the Genuine ATF WS (World Standard) Fluid Specification (JWS3324 or NWS9638).[16][17] This fluid is not backward compatible with previous Toyota fluids or Dexron fluids. Almost all 2004 and above Toyota vehicles with automatic transmissions use the WS fluid specification. This fluid absorbs moisture and should never be reused. Always use fluid from an unopened container. See Toyota bulletin T-SB-003-11

Toyota asserts that under normal usage, the fluid has a 160,000 km (100,000 miles) maintenance interval for inspection only; ATF-WS does not require any flushing or changing during the life of the vehicle; however, an inspection of the maintenance schedule of many Toyota vehicles reveals that there is a 100,000 km (60,000 miles) replacement interval if the vehicle is used on short trips, city driving, hauling heavy loads, trailer towing, or using a car-top hauler. Check your own maintenance schedule for your vehicle's requirements.

Understand, I'm not saying you can skip trans fluid replacements, and I don't skip them.