Strange noise on a cold start

Foques

Foques

New member
I suppose it is my turn. Not sure what this is, so figured i'd ask.

A couple of days ago truck didn't want to start. after about 5-10 minutes of trying, it fired up and never had an issue again.

However, since then I get this odd sound only on the cold start. It lasts for about 30 or so seconds, and sounds like high pitched noise; almost as if I have a vacuum leak.

It originates by the filter area. uploading a youtube clip as I type
 
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Before you said filter area, I was thinking fuel pump, but the only thing that I can think of that would be coming from the engine bay area would be a high electrical load? I know my second car (Hyundai) made that sound when I had HID projectors installed and turned ON.
 
Foques said:
"...A couple of days ago truck didn't want to start. after about 5-10 minutes of trying, it fired up and never had an issue again..."
Click to expand...

Hi Foques,

When you say... "truck didn't start"... Did it 'Not fire up' or just 'Not turn over'; as in no starter engagement? Also, how many miles on the clock?
 
rigtec said:
Hi Foques,

When you say... "truck didn't start"... Did it 'Not fire up' or just 'Not turn over'; as in no starter engagement? Also, how many miles on the clock?
Click to expand...
It was turning over, but not starting. I popped the hood open to see If I could spot anything (at 9pm.. yeah, right), them asked my woman to try again, and it started. very odd.
TBH, it may have been the aftermarket immobilzer glitching, now that I think of it.
Bevo said:
Probably your secondary air injection system making the noise. If so, it's normal.
Click to expand...

That's what it feels like, i just have not heard that before.

video:
 
Foques said:
It was turning over, but not starting. I popped the hood open to see If I could spot anything (at 9pm.. yeah, right), them asked my woman to try again, and it started. very odd.
TBH, it may have been the aftermarket immobilzer glitching, now that I think of it.


That's what it feels like, i just have not heard that before.

video:
Click to expand...

Mine makes the same noise. Always has.
 
Foques said:
It was turning over, but not starting. I popped the hood open to see If I could spot anything (at 9pm.. yeah, right), them asked my woman to try again, and it started. very odd.
TBH, it may have been the aftermarket immobilzer glitching, now that I think of it.


That's what it feels like, i just have not heard that before.

video:
[]
Click to expand...

From my lurking on the 4th gen forum and general reading regarding the Secondary AIP system, the system kicks in on cold starts below 40 degrees (don't quote me exactly but that temperature sticks out). You picked up a 2015 sometime during summer so it would make sense you wouldn't hear the noise until now. As Bevo and others mentioned that is the likely cause.

The Secondary AIP system dumps air into the exhaust during cold starts to meet EPA requirements. It was included on the 4th gen V8s, Tundra V8s, and 2013+ 5th gen 4Runners.

OA
 
thank you for putting my mind at ease, chaps.

I do not recall my 2012 runner make that sound.

here is what it sounds like with the new intake on

 
aha! Thank you so much, this explains it all.

Is there any documentation I can read on this, by chance? I've not seen this stuff before.
 
Its stupid emissions thing that helps that catalytic converters heat up faster by introducing fresh air into the exhaust . I'm really glad that my truck does not have one in that they tend to be a very common point of failure and are surprisingly expensive to repair. I have no idea why they brought it back. It was on some of the older Toyota trucks (then not there i 2010-2012/13) and now it has reared its ugly head again. I'm guessing it has something to do with lower cost catalyst being used again (or maybe stricter EPA cold start emissions standards).
This video explains how it functions pretty well...
<iframe width="420" height="315" src="https://www.youtube.com/embed/Zj-_bAiPq9Y" frameborder="0" allowfullscreen></iframe>
 
Last edited:
wfo9 said:
Its stupid emissions thing that helps that catalytic converters heat up faster by introducing fresh air into the exhaust . I'm really glad that my truck does not have one in that they tend to be a very common point of failure and are surprisingly expensive to repair. I have no idea why they brought it back. It was on some of the older Toyota trucks (then not there i 2010-2012/13) and now it has reared its ugly head again. I'm guessing it has something to do with lower cost catalyst being used again.

This video explains how it functions pretty well...
<iframe width="420" height="315" src="https://www.youtube.com/embed/Zj-_bAiPq9Y" frameborder="0" allowfullscreen></iframe>
Click to expand...

CARB is why.
 
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