VF SSV rough idle when stopped at Lights Etc..

[Scottay]

Hi All,
Just a quick question when stoping at a set of lights I have noticed a slightly rough idle is this something to do with the car dropping back to 4 cylinders (AFM)? I've only had the car for a week now so I'm not sure what is normal yet? Just need to know if this is fine or if it needs to go back to the dealer before it's too late.

Scottay

 

[Forg]

Someone who's used to a rotary would probably say any reciprocating-engine idle is rough ... I'm used to a 1970's Volvo 4-cylinder & a GM3800-II, so to me our L76 (L77?) VF idles quietly & smoothly ... I think maybe you have to define "slightly rough" (although I don't know how!).

I don't think it deactivates cylinders except at highway speeds.

Is there any chance it's had an aftermarket tune?

 

[someguy360]

It depends how sensitive you are.

In my opinion all GM pushrod engines shake a little at idle which can get transmitted through the cabin.

I find it was worse with the old 304 as they had solid rubber mounts and not a whole lot of flexibility so it tended to shake the car a little, even my L98 with new genuine mounts has a really small bit of a shake at idle, some people don't notice it, I do.

An aftermarket exhaust will also tend to make the idle a little rougher I have found.

A LS engine will never idle like a BMW/Euro V8 etc.

 

[mantaray56]

Could be fuel, try BP ultimate 98.

 

[CONROD]

Normal Trait :smoking:

 

[revster]

Well I have a '14 Calais, 6 .0 auto. Tuned and bolt ons and runs E85. No rough idle at all. AFM turned off but that matters little at idle.

 

[Scottay]

Thanks Folks, Been on holidays so it's taken me a while to reply.
Will try BP and see, I have added custom Exhaust & I seem to be getting used to it.

The main reason for the question was that when I picked the car up from the dealer they had left the radiator cap off so it overheated for a very short time. I thought maybe that was a problem that could get worse.
All seems to be good now.
Regards,

 

[Forg]

I was taking more notice over Chrimbo as a result of this post & others.

I can't feel any roughness at all, maybe it's about engine-mounts as much as anything else but the car just doesn't vibrate when the engine's on.

I can definitely hear squeakings & clickings & rattlings & what sound like normal goings-on under the bonnet, albeit not with the windows closed & the aircon on. If parked by the side of (or near) a road with traffic on it, I need to use the instrumentation to know the car's running.
I don't usually drive to work, but I parked last week between one workmate's current-model BMW 520i and another workmate's Porsche Cayman GT4. The BMW (which is admittedly a coupla years old now) does seem to make much the same normal-sounding mechanical noises from the engine-bay as the V8 VF; the Cayman, however, is eerily quiet mechanically, probably because (a) it's built AMAZINGLY well in every way you can think of, and (b) there's so much sexy exhaust-noise going on.

 

[Scottay]

Took it for a bit of a drive today & now I have the new Exhaust (Cat Back) on it the best way I could describe it would be that it's almost like it is misfiring every now and then but, I'm almost at refill stage so I'll try the BP fuel and see what happens.
Will report back soon.

 

[Nfsve]

I would say they all idle rough compared to say an sv6. Also they idle is a lot lower. Normal for this engine.