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Cold start, LOUD engine noise. Any ideas?

It is single digits and below zero wind chill. My first cold weather with this vehicle. Noise does go away. 3.3 v6 2006 sonata

WARNING: Might not want to use headphones.

Very typical noise…nothing to worry about.Mine sounds like a diesel under -10 but gets better when it warms-up.

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I believe that most of what I hear is simply the engine running at high idle speed when it is ice-cold, which is totally normal, and which should not be cause for concern. When it is extremely cold, it is not at all unusual for an engine to idle at 2,000 RPMs. However, if this high idle doesn’t reduce itself to normal idle speed (usually
~ 600 RPMs) within a few minutes, then there could be a problem. Once the engine is warmed-up, what is the idle speed that is indicated on your tachometer?

In any event, what does concern me is the extremely rough, uneven running of the engine for the first few seconds. When were the spark plugs last replaced?

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It has always started at 1500-1200 rpm then goes to 1000 sometimes 800 after 5-10 minutes of idling. After it is put in gear it goes to 600 rpm. I also cleaned the throttle body, but still has high rpm.

Someone mentioned the loud start up noise might be timing chain or tensioner. It has been starting fine the last two days though, nothing as bad as the video.

I did install a new alternator, about 2 months ago. I also took out 2 spark plugs recently to see their condition (and need to fix valve cover leak) and put the same ones back in, I torqued them to spec. The old ones were gapped at .040. Noticed high rpm of 2500-3000 right after old plugs put back in but went back to old rpm after driving it.

This is what the old plugs look liked.

Bought the car in March 2017 with 96070 miles now have 97400.

It only gets about 5 miles a day, majority of the time it is not running more than 30-45 minutes a day.

Oil does not seem to be too bad…

Sounds like valve clatter to me. Are you using the proper oil and changing it regularly? Otherwise pretty normal unless the valves need adjusting. Don’t know what Hyundai says.

Cars don’t care what the wind chill is, only people do. Wind chill is how fast a body will lose heat so it just means how fast the car would cool down when sitting. It can’t get any colder than the actual temperature. Weatherman use wind chill as a caution to how warmly to dress to reduce heat loss.


+1 to Bing and I would add that you should use an OEM or high quality oil filter to ensure best circulation of oil when cold. This car is spec’d by Hyundai to use synthetic oil and that makes a huge (positive) difference in cold startups in single digit, or colder, temps. If you are not using synthetic oil then you are only exacerbating your problem. Keep in mind that most engine wear occurs at startup, before oil can fully circulate.

I live someplace VERY cold and VERY snowy. I have used nothing but synthetic oil for over 20 years and my cold starts are very quiet, fast, and smooth.


The carfax showed regular oil changes at Hyundai dealership. When I bought it in March 17’ the dealer said he did an oil change. When I checked it before purchase it was lighter than what it is now and had a new Hyundai air filter, so figured they did do the change and the window decal says next change is for 98xxx miles. Then again not sure what type they used.

I was going to do the oil change after I replace the valve cover gaskets and spark plugs (weather had been an issue with that). Hopefully it lets up.

I have some 5 qt jugs of Mobil 1 full synthetic high mileage 5w20. I have enough oil so I Will just do a change right now, if I can clear some if this snow out of the parking lot.