Gas saving mode at 25mph

I drive like an old man. Stay under 30 if the sign says 25 mph.

In my new 2020 tundra when I take my foot off the gas at 25-30 mph it will go into gas saving mode and shut off the injectors. It will also down shift so the trucks speed will start to fall. When I hit the gas there is a clunk in the drive train. This clunk worries me.

If I speed up to 35 mph and do the same, no clunk. Goes into gas saving mode but it does not down shift. When put foot back on gas it just picks up like it should.

Do others also experience this clunk?

My wife tells me to just drive faster and problem solved.

Can a dealer reprogram the trans to not go into gas saving mode if it needs to downshift?

When the truck is cold it does not go into gas saving mode and when I take my foot off the gas at 25-30 it does not down shift or clunk. Only happens after truck warms up and gas saving mode starts kicking in.

 

Interesting.

 

Sorry Sir but you're mistaken. Tundras and Gas Saving doesnt belong in the same sentence.
The engines on the Tundras doesn't have cylinder deactivation.

 

Well I'll just come out and say that there is no such thing as a "gas saving" mode that shuts down injectors on a Tundra.

 

Hi!

I'm the guy in your mirror trying desperately to get around you. And the clunk is from towing any kind of trailer without a transmission cooler.

 

As far as the clunk goes, i think I've experienced this on a few occasions when i hit the gas just after a recent downshift that's not exactly complete, i expect this is probably normal. Experiment with giving it a second to adjust to the new gear before giving it gas, and it will probably be fine. This is what i did, and it seems to eliminate the clunk. Good luck.

 

I have the same With my 19, wouldn't worry much about it

 

What is it called then?

Take your foot off the gas while driving the gallons per hour go to zero, miles per gallon goes to 9999 and horse power goes to 0.

will start using gas if:

• put foot on gas
• slow down to 20mph
• put it in neutral

 

hahaha

 

What are you looking at? Do you have an aftermarket gauge setup?

 

Your just engine braking, no more fuel is being used and you'll continue to decelerate, if going downhill or braking the truck may downshift. Your mpg page will max out any other gauges will reflect max fuel economy, but your bleeding off all your speed and will burn more gas to catch up if your not going downhill or coming to a stop.

 

What is going on? Does he have an F-150 with cylinder deactivation and is on the wrong forum?

 

Well, what ever it is called, It causes a clunk in the drivetrain when turning off. Does anyone else experience it?
steps to reproduce:
warm up truck
get to 30 mph on a flat or down grade.
release gas pedal
wait for the truck to feel like it is slowing down by the engine
when it gets to 25 mph put foot back on gas -- does the drive-train clunk?

I went on a drive around and did more testing with it. seems start using gas by itself (no clunk) at 22 mph (can hear engine tone change and my scanguage will show it using gas at the next screen refresh). But when use the gas pedal at 25 it will clunk. The clunk seems to be coming from the engine.

Think the 2015 would not turn off the gas unless I was going much faster, I don't remember it turning off the gas under 30 mph (at least nothing I could feel in the drive train)

 

Friday thread!!!

 

You don't seem to understand what people are saying. Your Tundra is not turning off the fuel. There is no system in this truck for fuel preservation. The 5.7 L motor is an oldie, and it gives no shits about MPGs. I do not care what your computer gauges say about fuel economy, your truck is not turning off injectors. You take your foot off the gas and it will use a minimal amount, just like any pre 1990 engine would. This is old tech. You have no fuel preserving systems in this vehicle. Any kind of a clunk that you're hearing has nothing to do with your fuel economy.

 

I can assure you that all modern fuel injected engines (Toyota 5.7L included) stop injecting fuel under most coasting conditions.
This is called deceleration fuel cut.

 

So you're telling me that when I'm coasting down a hill, and my engine is still running, it's running without fuel? How is it maintaining combustion with no fuel?

 

No, you are correct. The motor is STILL RECEIVING fuel from the throttle body. Granted, it is the minimal amount, to keep the motor at idle, but it is indeed, still receiving fuel.

 

And that's why in my first post I said that it is running on minimal fuel, but it doesn't shut off fuel the way cylinder deactivation does. Tundras don't have anything like that. They're operating on older technology. That's why I bought one.

 

The wheels are turning the axles, which turn the differential, then the driveshaft, then the transmission and finally the engine through the torque converter clutch.
There is no combustion happening, the engine is just spinning over.

 

Cylinder deactivation shuts cylinders off during cruise conditions, not during deceleration.
Tundra does not use cylinder deactivation, but it certainly uses deceleration fuel cut.

 

You are incorrect in that statement sir.
There is no fuel injected during deceleration fuel cut and there is no combustion in the cylinders.
(I am a Toyota master tech)

 

so that glorious V8 engine sound that I hear through my exhaust even while coasting down a hill is what? That's combustion happening inside the engine. If it's ceased combustion, even if the engine were being turned, it would stop making the noises associated with combustion. It would just be the mechanical sounds of the engine moving, rather than the small explosions of combustion that make that beautiful V8 sound that is so nice.

 

Here is a page from the repair manual talking about torque converter lock up during deceleration fuel cut, allowing the engine to be turned by the wheels during deceleration through the locked up TC clutch to save fuel.

 

I understand all of that, and I'm not saying that anything that you said previously isn't true. I'm saying that fuel is still used while coasting. It does not cease combustion. Fuel economy is improved, but fuel is still used.

 

Under a lot of coasting conditions (but not all), there is no fuel being injected into the engine whatsoever.
Once the engine rpm drops to a certain point, or the accelerator is applied, or the transmission is put in Neutral, fuel injection restarts.
There is really no point for me to try to convince you any further.
I have been a shop foreman at a Lexus dealership and a Toyota master tech for 15 years.
You could just google “deceleration fuel cut” and read up on it.

 

Viktor,
Is having a clunk noise that you can hear/feel normal when the accelerator is applied during the 'deceleration fuel cut' normal?

Has Toyota changed the system between 2015 and 2020? In my 2015 never heard/felt this.

 

You might be feeling the torque converter clutch disengagement but it should not really be noticeable.
Since the truck is brand new, the best thing would be to stop by the dealership and ask for a road test with a tech, as well as asking them to let you drive another 2020 model to compare.
It is very hard to diagnose over the internet...