Start Up Sequence? (Noise Investigation)

Preface: This is a really, really technical question and I would be shocked if anyone can answer this right now. However, it won't get answered if I don't put it out into the universe...

Question: Does anyone know the start up sequence of this new engine (non-hybrid)? Meaning what happens mechanically & electronically before the starter engages?

Reason for my asking (wall of text warning): I worked in a mechanic shop for ~5 years throughout college so I feel fairly "advanced" for a shade tree mechanic. Because of that, my ears & brain have been conditioned to always listen for "trouble" sounds. When starting my new Tundra, I always hear the usual sound pre startup noise of the fuel pump pressurizing...no big deal, normal. However, if the truck has been sitting for a long time (i.e. engine is cold), I will hear a mechanical sound almost like a clunk. It kind of sounds like a valve snapping shut, or a gear engaging. It's definitely not an electrical sound like the "click" of a solenoid engaging. When I stand outside of the truck and remote start the truck, I can hear it and it comes from back half of the drivetrain...almost around the exhaust manifold or the transmission/transfer case area. It's louder when standing outside, but I can even hear it in the cab. It's tough to catch because if I shut the truck off and restart it (even if it's still cold) it won't happen again. It's only ever on the initial startup when it's been sitting cold. I'm at 4,000 miles and I only noticed it happening in the last 500-1000 miles. While I've worked on many cars & trucks throughout the years, this is the first turbocharged engine I've ever owned. I'm trying to track down what might be happening since it's so tough to replicate. I know when I mention it at my upcoming service appointment in a couple of weeks, they (probably) won't be able to replicate it since the truck won't be there long enough to go fully cold.

 

No idea, but have to recorded the sound? Could you attempt to isolate it by remote starting it while laying underneath the truck?

 

My 2022 tundra SR5 has 354 miles on it and it’s making the same clunk sound right at startup, usually when the engine is cold. This is not a normal sound and I’m definitely concerned . I’m about ready to take it to a Toyota dealer to check it out.

 

Let me know what happens if you do take it in. It comes and goes for me now. I tried to catch it on a video but it stopped doing it shortly after I made this post on Feb 3rd. It probably went 8 days without doing it and then it started doing it again in the last day or so. I’m going to mention it to my dealer when I take the truck in the for the 5k service this Thursday. Of course, I’m worried they won’t be able to replicate the noise. Hopefully, they’ll be able to take a look at it.

 

Next time try starting it with the hood up and see if it's louder. There's a secondary air pump on newer model Toyotas that dumps air into the exhaust on cold starts to get the cats up to operating temp faster.

 

I have heard/felt a clunk on cold starts as well. I am working with my dealer and regional Toyota field engineer on a couple other issues right now, I wonder if this could be related to the transmission behavior that they are investigating.

 

I hear this as well on cold starts!

I think we’re all being paranoid of the vehicle. This forum makes it worst. I have a list of items I want them to check out when I get in for service at 5k.
1. Wind noise
2. The noise at start up.
3. I mentioned this in another thread and was told it’s normal in turbo vehicles. If you do not let the truck warm up enough. Reverse out the driveway and out in D is has a slight lag. Also the first acceleration. After that never feel it again. I warm my truck up now everytime before going somewhere and never experience it.

 

I see a new warning note in the remote start section of future owners manuals

 

I might’ve missed it. What transmission issues are they looking at?

 

There is a lurch when transitioning from slowing to going at very slow speeds, 1-3 mph. Happens even after truck has been warmed up and driven for a bit. I started another thread on it - Transmission lurch at slow speeds.

 

How many miles do you have so far? Keep us updated on what Toyota tells you.

 

I agree this forum likely makes it worse sometimes. haha. This could be no problem, or it could be indicative of something else. I guess it always helps to know if others experience the same noise.

Side note...I have noticed the transmission lag when I back out of my driveway, especially on super cold mornings. I've already developed the habit of shifting into Neutral for a 3 count and then shifting into Drive. It seems to help with the lag.

 

3,094 miles. I back the truck into our garage, I don’t notice any lag when driving out. From complete stops the truck is fine, just the transition at slow speeds, which I did not notice at all in 2021 Tundra I had. My wife has driven both trucks and immediately commented on the lurch on her first drive in the 2022.

I’ll post future updates in the other thread. https://www.tundras.com/threads/transmission-lurch-at-slow-speeds.102878/

 

I think there’s an electric oil pump in the transmission. It could be that firing up at ignition on before starting the engine.

 

Ahhh. That might be it. The most plausible answer I've heard so far. When I crawled under the truck and managed to hear it...the sound seemed to originate toward the front of the transmission. If it's an oil pump inside the trans, it's def loud occasionally. Parking angle doesn't seem to impact it because I've noticed it on level ground and in my driveway.

 

I heard this clunk the other day when I started the truck with the door open.

 

I took my 22 tundra to have the clunk noise checked out. Fortunately the tech heard the noise at startup too. They just happened to have a 22 SR5 off-road tundra as one of their rental vehicles. The tech went out and started the other tundra and he heard the same clunk/knock sound. However, they have no idea where it’s coming from and what’s causing it. Their contacting Toyota to see if they have an idea. I’ll post whatever info the dealership finds out.

 

Nice. Thanks for the follow up. I mentioned it at my 5k service appointment and the dealership kinda brushed it off since they couldn't replicate it. I'd be interested to hear what your experience is.

 

I just wanted to add that I have recently noticed this knock too. I have 4k miles and like you said, it only happens on cold start. If I turn it off and back on, no knock.

 

Got about 1300 miles myself and have always noticed this noise. Its not all the time for me but is often enough where I've heard it dozens of times. Can't speak to whether it's isolated strictly to a cold start but can say it's not always when the engine is cold as this morning it did not occur and the truck was sitting all night in garage.

Wondered to myself many times whether or not this was normal...

 

VCT/VVT could be locking or phasing to a cold start position.

Have you opened the hood and asked someone to assist with your cold start?

 

I'm about to hit 10k and the noise continues occasionally. It's never caused any issue. Just the occasional "soft clunk" on cold or "warm" start. I've noticed it most often when I start my truck after sitting for between 2-8 hours. I've never noticed it when starting my truck after it sits 12+ hours overnight at my house.

It's definitely not in the valve train because it's not coming from the top of the engine. I've had the engine open at times trying to listen for it.

When it happens, it always sounds like it's coming from bottom or back of the engine. Like the the exhaust manifolds or transmission bell housing area. Who knows? Maybe it's the dreaded wastegates for the turbos slapping shut on cold startup? I dunno. I'll mention it again to my dealership at my 10k service on Monday, but I doubt they'll catch it. At my 5k service, they couldn't replicate it so they just chalked it up to normal operation.

 

If you want to check with a stethoscope, the transmission electric oil pump is right near the back of the pan. It’s the white part on this cutaway of the transmission. There’s also a front oil pump but it’s driven by the engine. You can kind of see the chain between the torque converter and the gears and the oil pump itself is in the lower left cutaway.

 

It sounds similar to when the truck auto stops and then restarts again at red lights. Thoughts?

 

I have the same thing, and am not really concerned with it, especially seeing that this is common on most, if not all '22s.

 

I've got the noise as well. Same exact description. It sounds like a "clunk" at startup. I'll talk to my dealer at 5k service, but I'm sure they'll pass it off as normal operation.

 

Had the same thing, took it to the dealer and they said they found nothing wrong with it.

 

Well...I guess I'm glad to know that it seems fairly common.

I'm sure it's just a normal operation of a pump or something else mechanical. If it fails...I just hope it does it during my warranty period. haha. Otherwise, I'll just keep an ear out for any changes to the noise over time. I'm about 11,000 miles and it hasn't impacted anything yet. [Knock on wood]

 

https://youtu.be/XE7_1k0A4VE

I believe I captured the noise we are talking about. Listen around the 3-4 second mark. Curious what everyone thinks

 

I definitely heard it in this video you posted.
Mine does not do that, at least for now!
It only has 112 miles on it at this point.