Weird noise on cold start?

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

Loose heat shield?

Your (vertical) cell phone video doesn't do a great job capturing the audio...

huh

It sounds to me like a small exhaust leak and when it gets warm it expands and the noise goes away.

Vibrating heat shield.

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.

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 ???