Idle issue or working as intended?

Just picked up a new to me 2020 Platinum 4WD, 43k miles, my third 5.7 (previous Tundra and a Sequoia which I still have). Had a solid service history of oil changes every 5k, which is good enough for me on a Tundra with 43k miles. Test drive went well, I looked for the common issues, all seemed well.

After taking it home, when I started it the next day, the idle shot up to about 1600 for almost a minute (normal in my experience), dropped back down to 700 (normal in my experience) and then bobbed up and down slightly (100 RPM or so) a few times. Figured it was the A/C or I bumped the steering wheel, so I shut the A/C off, it still bobbed up down slightly. Steering wheel was vibrating idling in park more than my old Tundra which was 10 years older than this one, really the entire cabin was shaking a little. When I revved it up in park, the shaking got much worse. I started by just throwing some Techron in it to see if it was some bad gas left in it, ran it half a tank, same issue. Checked engine air filter, checked MAF sensor. Had a mechanic friend of mine check it out, he checked a few of the same things, no codes although some strange behavior from O2 sensor (showed as 0 for a bit and then all popped up on scantool at once). Said everything looked and sounded fine. Took it to Toyota, they said the same thing. I test drove a 2019 Tundra Platinum to make sure I wasn't crazy, and the vibration in idle and when I step on accelerator in park isn't there.

Am I losing my mind? My older Tundra and my 1 year older Sequoia with 3x as many miles doesn't shake one tiny bit in idle, and definitely not when I press the accelerator in park. How can the newest, least mileage 5.7 I have owned feel the worst? How can it feel different than the 2019 Sequoia I have, or the 2019 Tundra I test drove? The truck drives perfectly on the road, the highway, it's just at idle that it feels worse than a 14 year old Tundra. My wife notices it, but she has only driven it once. Anyone have any idea or is it just one of those "deal with it" issues? Thank you.

 

Is it a FFV?

 

Maybe it has a bad motor mount? I know that seems unlikely given the mileage, but you never know. Any oil leaks or signs of past oil leaks underneath? An oil leak can chew up rubber components quickly.

Edit: to answer the tread title, definitely an idle issue and not working as intended

 

I specifically went for non FFV because of the problems. Fifth letter of VIN is Y which was thr easiest way to tell when online shopping, or am I mistaken?

 

That was what I thought initially too, I doubt they even checked the motor mounts at 43k miles. They didn’t even say it was idling odd, they said it seemed fine, but I’ve driven the 5.7 for so long that I know how it’s supposed to feel.

 

Yea mine idles buttery smooth. I chased a vibration at idle for a long time in my Tacoma and after a million far more complicated things failed, a simple transmission mount (aka rear motor mount) solved it.

 

My truck has a smooth idle as well. If not motor mounts, maybe something being driven by serpentine belt has a problem, revving it and vibration increasing could be a balance issue with something; alternator, PS pump, AC clutch/compressor, etc…

 

I’m definitely going to investigate the motor mounts. I don’t feel comfortable jacking up underneath the oil pan, so maybe I’ll take it to a different dealer.

 

Just an update in case anyone has the same issue in the future and finds it on search, still not resolved. Things that have been checked- throttle body cleaned, MAF sensor cleaned, idle relearned, mounts checked, no signs of (external) oil or coolant leaks, have been running it with higher test gasoline to rule that out. It also started puffing little bits of blue/white smoke out on startup (followed by the normal white condensation puffs that my 5.7's always have on startup) and heavy acceleration. Took it to a really good and honest mechanic and he said it feels normal to him, did notice the blue smoke and thinks it is running a bit rich (which is what I wondered about since there is fuel residue in tailpipe) and is nothing to be worried about. I'm gonna give up looking for the cause at this point, even though my old 5.7 and my current 5.7 Sequoia run like a completely different vehicle, this Tundra feels like I have massaging steering wheel and seats and I'll just have to live with it.

 

I could be wrong, but I thought bad motor mounts stop shaking when you rev the engine. Is it burning through oil in between oil changes any? How's the fuel mileage? As crappy as expected or worse?

I know you said you have a really good honest mechanic but it might be worthwhile to take it to another trusted mechanic or someone that specializes in Toyota engines to get a second opinion.

 

Not burning through any oil or coolant, fuel mileage seems to be the same as what I've always gotten- between 13-15 city/highway. At this point I've taken it to a friend who is a mechanic, two Toyota dealerships (one didn't even pull the truck out of the parking spot so I went to another), and what most consider the best Toyota mechanic in my area who only works on Toyota/Lexus. I think it's one of those things that unless you have driven this engine consistently for years on a daily basis, you aren't really in tune with how it should "feel". If I were a mechanic I would think I'm crazy, which is specifically why I went and test drove another near model year Tundra to make sure it wasn't in my head. It's one of those issues that I'm pretty sure isn't a big deal, it's just annoying when I'm sitting in my truck waiting for my wife in the store and feel like I'm being massaged.

 

I have never noticed feeling anything from the engine idle, or rpms changes at idle. I do hear mine rev down and quickly rev up as the ac compressor engages, but I don't feel it. I hear it best at drive thru with window down. But really don't feel it.

 

Yes, I don’t feel anything on my Sequioa or my old Tundra with the AC off. With this one it’s a really deep vibration that is constant in park, amps up as I press the accelerator in park, and only goes away when I shift to drive. I’m at a loss.

 

Yea maybe just get used to it unless it gets worse. Mine has the valvetrain tick I Hear at idle and I keep thinking something was wrong, but it's a work truck that idles alot and 70k later nothing has went wrong. So I just stopped worrying about it. I have a co worker with a 2021 Tundra and his does not have the tick mine does.