Feels like it's starting on 7...

[luca1290]

Hello everybody,

on cold starts I have the feeling the engine is having some kind of "resonance" at about 1000 RPMs, I can hear the engine speed fluctuating in a sinus function... I don't know how to say it better.
When I put the car in gear I can hear it through the drivetrain, she pulls the same way you can hear the engine speed fluctuating(a bit more / a bit less / a bit more / a bit less...). It's probably the engine shaking a bit.
Or maybe I just hear it when I put her in gear, it seems like that if I wait a few seconds for the engine to settle down, than I can't feel it.

No misfire detected, no gas smell, no sputtering. Lasts a few seconds and then it's gone. It's somewhat similar to the roughness you have when you are on longer gears with the 10R80 and giving a little gas, but I know that is a characteristic of this drivetrain.

It's probably normal, but I can't figure out what is causing it (firing order?).

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[Duston@Lethal]

Sounds like plugs, pull them and see if any are fouled.

 

[Synergy720]

Hello everybody,

on cold starts I have the feeling the engine is having some kind of "resonance" at about 1000 RPMs, I can hear the engine speed fluctuating in a sinus function... I don't know how to say it better.
When I put the car in gear I can hear it through the drivetrain, she pulls the same way you can hear the engine speed fluctuating(a bit more / a bit less / a bit more / a bit less...). It's probably the engine shaking a bit.
Or maybe I just hear it when I put her in gear, it seems like that if I wait a few seconds for the engine to settle down, than I can't feel it.

No misfire detected, no gas smell, no sputtering. Lasts a few seconds and then it's gone. It's somewhat similar to the roughness you have when you are on longer gears with the 10R80 and giving a little gas, but I know that is a characteristic of this drivetrain.

It's probably normal, but I can't figure out what is causing it (firing order?).

If you start driving immediately after cranking the engine for the first time in more than 5-7 hours. It’s gonna sound like that. Mine does that (if it’s what you’re referring to). Like it’ll be a very harmonic sound coming from the engine in the middle of shifts. I don’t recommend driving it like that. Give it some time to warm up. Maybe 30-45 seconds after first start.

 

[luca1290]

If you start driving immediately after cranking the engine for the first time in more than 5-7 hours. It’s gonna sound like that. Mine does that (if it’s what you’re referring to). Like it’ll be a very harmonic sound coming from the engine in the middle of shifts. I don’t recommend driving it like that. Give it some time to warm up. Maybe 30-45 seconds after first start.

Yes, like an harmonic resonance, you nailed it. Yours is probably a very good advice because harmonic resonances tend do grow on themselves.
Any petrol engine can exhibit little bit of roughness at cold, and I'm relieved yours does the same.

It would be interesting if an engineer or someone with deepest knowledge than mine can articulate why on this engine shows that in this way.

 

[mejohn50]

Cold start emissions reduction (CSER) strategies retard ignition timing for a period of time to heat up the catalytic converters. Retarding the timing can change the way the exhaust sounds. That’s probably what it is.

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