Startup engine idle speed

I've found this interesting, and am curious about how other trucks act.

When I first bought my truck, mid March I noticed when starting the cold engine it would instantly reach 1600rpm, then of course idle speed would start to fall. But recently I've been noticing that the cold start idle speed is like 1400rpm. I always felt that 1600r's seamed kind of high, not that 1400r's is a lot slower but it is definitely noticeable.

The thing that's curious is how did this slower startup speed manifest its self? My thought is maybe part of a software update downloaded by the truck. I have had updates show up on the main display on the dash that I accepted and installed, is that possible?

 

I thought those updates were for Entune only but I could be wrong. Is it possible the dealership updated the ECU when you were in for something else?

 

My 17 starts with enthusiasm but quickly scales back to about 1000 rpm and then finally on back to around 700. The outside temperature could have something to do with the start cycle

 

My 19 does the same thing. I just figure with how many Gen 3 Tundras there are with the exact same engine and nobody else worrying about it that it’s normal. Kind of like the clicking sound or the bump when first starting. Or like your ankles if you are older. Hahaha.

 

Agree thinking those updates for Entune, and I did have the truck at the dealer 9/15 for a wheel alignment check and they did the turn signal wire fix. But I would think if they did any software updating it would have been documented in the paper work.

 

I also realize ambient temperature would play a roll, but living in "Minnesnowta" its cold here a lot. Certainly in mid March and October, November overnight temps can get rather chilly.

This isn't something that's concerning me, just a curiosity more than anything.

 

I've upgraded to my truck to the Auto Climate Controls, but I've noticed that until the engine is at full operating temperature, the revs will stay elevated somewhat if the Climate controls are set to Defrost and/or Auto. If I'm sitting there in P/N and partially warmed up, I can press Auto/adjust Defrost on/off, and the revs will increase when these functions are on. Play with that on yours just to see if the same thing happens.

Additional thing that I noticed: When the revs are slightly elevated pre full operating temp, I've noticed that when I place the transmission in gear, the computer will lower the revs so the truck won't "bang" into gear.

 

I believe the change in engine speed when engaging Auto or Defrost in the climate controls, is because of the compressor engagement.

 

Yep

 

I used Techstream to restrict the A/C to only come on with an A/C button press. It will not come on automatically under any circumstances.

 

Now that is something I would love to have done with my truck!

 

Does the A/C light or LED come on every time AC is turned on automatically? I mean before your techstream tweak.

 

So somewhat similar. Looks from your account it’s a 2020 just like mine. I have less than 4K on my odometer but I installed an exhaust and a intake. Mine kinda went down after doing so I figured the ECU adjusted for everything properly and didn’t need to idle as high. But I would consider as you’ve “broken in” the truck maybe it’s mapped the idle speed bwtter?

 

It did, yes.

 

Hadn't considered startup idle speed slowing after engine break in. I have about 5600 miles on it now, maybe your on to something.

 

Cold engine start my truck always revs higher in RPMs for maybe 30 seconds before it idles down some. Doesn't matter if it's hot or cold outside, fan on or off, AC on or off. All my Toyotas have done that I just thought it was normal.

 

I m not too fond of that crazy loud fan at startup, but when I turn the key it s like it cant wait to start. It s almost startling sometimes.

 

I agree with Nick's comment regarding the ECU. When you install any aftermarket intakes, they recommend you disconnect the battery.
This step performs a few things, but it will clear the long term fuel trim map file.
When a truck is brand new , it is still learning and writing the fuel trim file.
Once that file is established, it will be referenced to help optimize start-up and idle.
When comparing cold-start to cold-start, is it at the same weather conditions and temperatures? or just cold?

 

I was just comparing the cold start initial rpm speed, not taking specific temperatures or weather conditions into consideration. Nothing scientific and I haven't disconnected the battery, at this point Nick's thoughts on the ECU adjusting start up speed seem the likely scenario.

 

These are what I have available in the ECU regarding idle rpm and airflow on my 2018. 3rd picture I opened the Base P/N(park/neutral) table, coolant temp in white numbers, target idle speed numbers in color below.

 

I think all Toyota’s have the high idle. Hell my grandmothers 94 Avalon has the same high idle startup, kind of annoying but at least you know the major components are warmed up before you start driving

 

Assume temps in Fahrenheit?

 

Yes

 

Wow I bought my 2014 Platinum used an 16 months ago w/ 95k miles and I didn’t get a check to check things like engine idle speed at first cuz I was in accident a month after I bought it and it was still winter. Now I have it for the first time in “warmer weather” 65 temp day time and 40 something at night and it takes literally 5 minutes for my idle speed to drop from 15-1600 to 800 rpm. I did install a performance tuner but I’d think that wouldn’t affect it that much cuz that’s a crazy long time for the rpm to be that high. I’ve typed this whole message since starting my truck and it just got to 750 and it’s been 8 minutes .

 

My 17 is the same. At start it is at 14-1500rpm. Takes about 5m to come down. I just sit and wait until it is under 1000 rpm. I'm never in a hurry to get anywhere.

 

I just wonder why it does that and if something is wrong with it… honestly I’m always in a hurry as a single dad. I tboned in the accident I had and it sat at one shop for 7 months and when I finally started to check on it the last month to light a fire under the guy, I realized he wasn’t making the repairs promised or properly. The driver door beam was bent and needed the door replaced and I literally caught him trying to take the dent out to after making more dent’s removing the emblem. He also heated up and bent the damaged lift kit parts to reuse them. I had to send a tow truck to get it and the guy refused to give me a refund (he promised 6 weeks to fix it and was clearly committing insurance fraud as he’d already been paid) so I took it anyway and my boss gave the loan for $6k to get it finished with an additional $2.5k from my insurance cuz he missed that much damage he wasn’t going to repair. My point is it sat for so long and had been molested by that shmuck so I’m concerned they missed something maybe or at the very least maybe tuner is doing it.
Have you ever done any engine mods… ie tuner, intake, exhaust… to your ‘17? Long post I appreciate it if you read all that lol.