Sluggish over 80 Degrees?

I’ve have my DCLB auto 3.5 for 4 years and 50k miles now. I know what it is and what it’s not. It’s lifted 2” on 5100’s with icon leafs on 265/75/16 Toyo at3’s. I also have an ARE cap. As the New Jersey summer approaches, I’ve noticed a sharp decline in low end power when the temperature is around 80 degrees and up.

In the morning, when the temp is closer to 60, I can chirp the tires and it moves as fast as I’m comfortable driving it. However in the afternoon heat, it can’t get out of its own way, specifically in 1st and 2nd gear. The transmission seems to upshift faster than normal and hold the higher gear despite how much I hit the gas. Highway driving seems to be normal for what it is.

Any ideas? I was thinking maybe a fan clutch issue robbing power? Aside from the mods above, the truck is stock. Is this par for the course as these truck get some mileage on them?

 

I'm just throwing poop on the wall here, but could it be a dirty air mass meter wire?

 

With that, it’s worth noting I have a KN drop in filter that I clean religiously every 6 months.

 

Warmer air is less dense, reducing oxygen for fuel combustion, which decreases engine power and efficiency.

 

If it's one of those filters that you oil, that's probably the issue. Clean the air mass meter wire with some electric connector cleaner and put in a standard OEM paper filter and see if the problem goes away.

 

Interesting observation, I’ve noticed mine drives almost like a normal vehicle on damp cool days. The nicer it is outside, the worse it drives lol. I clean MAF every two years. It’s extremely noticable. Shifts smoother and more predictably. Wish I could correlate it with something and figure out why it’s happening.

Edit: I’ve experimented pulling the AC compressor fuse thinking that AC had something to do with it (defrost runs whenever it wants) and the behaviour remained the same.

 

Coupled with the 'summer blend' of gas who knows.
We're hitting 105+ already but I haven't noticed any issues.

80 degrees you say?.... I'd be putting on a sweater.

 

I tried 3 different after market air filters in my 2016 TRD off road.

In climbing up 5,000 ft elevation at 100kmh with a heavy load, on the same stretch of highway, it was a pig for performance. Surprised the hell out of me that filters like Fram and others bogged it right down. Badly so. It was gasping for air.

So I put the OEM filter back in, and presto no performance issue on that hill.

I would never go after market on air filter again. On the flats and smaller hills you might not notice it so much, but under heavy load those filters were absolute crap.

Not saying that is the issue here but a cheap change to make and test it with OEM air filter.

 

that’s interesting. I run my KN dry. I’ll try an OEM filter. Do you use a “Toyota” branded filter or generic oem spec?

I will also be checking my MAF.

 

I now only use the Toyota OEM filter from the dealer. The results with the other filters was surprising.

Not until I was hauling up that hill, which I do about 20 trips per year, did I discover how much those other filters affected performance.

 

I picked up an OEM filter and a can of MAF cleaner today. Stay tuned for updates!

 

Follow up! I wanted to make sure I had enough data before posting.

Cleaning the MAF (which looked brand new) and running a paper air filter definitely made a difference. Not exactly night and day, but noticeable. Fuel economy did not change much at all. I still averaged around 19 mpg on 87 octane.

After a few tanks a fuel I switched over to 93 octane(from the same Wawa). This was a definitively noticeable difference in power, throttle response, and acceleration. Additionally, fuel economy spiked up to a 21mpg average across 5 tanks for the same commuting that got me the first baseline of 19mpg.

I have since switched back to 87 octane and immediately heard more knocking from the engine under load, and have noticed less power. Keep in mind this data only applies when temps are over 80. In the 60’s and low 70’s. The truck runs great either way.

Thank you all for your input!

 

You really cannot reliably measure engine output by the ability to “chirp the tires”. There are too many variables. My guess is the your tires had more traction when it was warmer out. Have you seen drag racers do a burn out before a race? It’s because warmer tires typically have more traction.

FYI, in every thread where someone complains about an engine not running right, invariably someone suggests cleaning the MAF sensor. Take it with a grain of salt.

I think the differences between 87 and 93 octane are likely in your head. Ditto for air filters. The placebo effect is real.

 

For the record, I’m an equipment fleet mechanic with 20 years experience. So I know engines, just more in tune with off highway and diesel stuff. Cleaning the MAF was a free exercise and made sense based on the symptom.

Secondly, my average 0-60 time dropped over 1 second from 9.4 to 8.3 seconds with all the above changes. So while I can’t quantify my gains by variable, I truly feel the fuel change was the biggest factor. And the math behind the fuel economy is iron clad. I’d bet my paycheck the paper filter and fuel change made measurable performance changes in the truck.

 

I know you are right, at least in my case.
My V6 runs much smoother with the 93 octane, and I get a couple extra miles per gallon.
The 87 octane stuff definitely hurts performance for me and makes the truck sluggish
I've tried several different brands of gas the results are the same. The really cheap gas is the worst