Automotive

Weird noise on cold start?

  • Last Updated:
  • Oct 25th, 2019 1:02 am
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[OP]
Sr. Member
Jul 26, 2013
611 posts
535 upvotes
CALGARY

Weird noise on cold start?

Hey guys
I have a 2012 civic lx
It's been making a weird rumbling noise when started cold for the last 2-3 years. It goes away after the engine gets warm
Not sure what it is about
Made a video here, kind checking it out?
7 replies
Deal Fanatic
Oct 26, 2008
6389 posts
2039 upvotes
BC
The classic answer for a cold start rumble, on any car, that goes away when engine warm - is piston slap.

But I don't think that is happening here.

9th generation Civics have a fairly common issue with a scraping noise on cold starts that dealers have apparently been unable to diagnose correctly.

Seems like replacing the VTC actuator, or the rear engine mount, or the drive belt tensioner doesn't fix it.

Most agree it is an oil pressure problem though. Some owners fix it by ensuring oil is always filled to the Max line and trying to park on a downslope!

(I usually argue that fluid levels shouldn't automatically be filled to the Max line, and there is a reason for having a Min to Max range with midway being optimal.
But I concede with engine oil level it is probably best to shoot for close to the Max line in general.)

It is a bit concerning that this noise only emerged after four years of ownership. That does suggest something has worn and not just a 'feature' of that engine.

Of course it could be unrelated to the engine and be something like the exhaust system rattling until the engine has settled down after a cold start.
(But maybe that was the thinking behind the rear engine mount being the problem.)

Despite making what most believe to be exemplary engines, Honda does seem to have had problems the past 2 decades.

You may just have to live with the noise and be glad it is not something like a cracked block that 8th Generation Civic owners encountered.

Long owners forum thread here
Last edited by macnut on Oct 24th, 2019 12:07 am, edited 1 time in total.
Deal Guru
User avatar
Sep 3, 2003
12284 posts
715 upvotes
Toronto
Loose heat shield?

Your (vertical) cell phone video doesn't do a great job capturing the audio...
Deal with it.
Deal Fanatic
Jun 11, 2005
8547 posts
2322 upvotes
Mississauga
It sounds to me like a small exhaust leak and when it gets warm it expands and the noise goes away.
Deal Guru
Feb 9, 2006
12252 posts
6803 upvotes
Brampton
Vibrating heat shield.
Deal Expert
User avatar
Jul 22, 2006
22095 posts
2763 upvotes
A cold start is different than starting it when it's already warm..
When it is cold, more fuel is added to the air/fuel mixture to make up for the lack of natural vaporisation. So the AFR (air-fuel ratio) is seen by the ECU to be leaner than usual (below the Stoichiometric ratio of 14.7:1) so it compensates for this with extra fuel to make up for the unburned fuel due to the cold. [...] the ECU increases the engine speed at initial idle to make sure that all of the excess fuel is being forced out of the cylinders quicker than normal.
https://www.carthrottle.com/post/why-ar ... s-so-loud/


Like RFD members here said, check the exhaust.
Member
User avatar
Sep 1, 2009
316 posts
252 upvotes
gta
Piston slap and rings are dry and rubbing -light weight oil /frequent oil top up /sea foam clean.

When was your last air filter changed ???
“I swear by my life and my love of it that I will never live for the sake of another man, nor ask another man to live for mine.”-John Galt 😎

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