mikecronis

So I have a 2012 GS manual and I've noticed that all LS3 owners get a bit of a hesitation on idle, like it's missing randomly every now and then.

Since I have the Diablo InTune tuner, there's an option to increase idle speed in various increments.

I think the LS3 idles at what seems to be about 650-700 rpm and I was considering raising that to 900 rpm. I'm at 6000 feet altitude. I suspect this might fix the cylinder-skip issue.

Also, does anyone know why the LS3 does this? Is the spark not firing or is it perhaps starved for fuel at idle a bit? I've heard spark-plug replacement has been marginally successful and smooths it out. I never had this problem with the LS1, albeit a significantly different design.

Al Gumby

Mine idles at 600 rpm. If this lumpy idle were a real problem, I think it would throw a code, which it doesn't. In fact, I think most folks here like the way their LS3 idles. No fix needed.

C7/Z06 Man

Stock or Intune; I have looked at my idle since new and it looks like its 525/550 rpms after warm up on my tack. I could raise it with the Intune but see no reason.

needcheese

Nothing like a small healthy cam.

JCtx

I don't like it either, but it's perfectly normal. Mine idles at something like 550, which is nothing. Plus the cam. Plus the crankshaft is obviously not very well balanced (it's a freaking Chevy ), so all contribute to a less than Lexus-like idle quality. Nature of the beast. By the way, I replaced the stock wires, which have something like 800-ohm resistance with MSD 8.5mm superconductors, and they made a small difference, but we'll never have a Lexus idle on these cars, no matter what we do. Maybe with idle at 1K or higher, but that'd be crazy.

drspencer

Toying with the idea of doing an LS conversion on my '71 350/270 base C3.

I've never driven a LS3 car. Does a LS3 have a rough, lopey idle in it's stock form?

Is a LS1 idle quality any better?

Thanks

mikecronis

Revive this thread? Ack! 2013?!
Anyway, yes. The LS3 is essentially a bored-and-stroked LS1 with a more aggressive cam (not really but sort-of). The cam is a tiny bit lopey by a tiny bit compared to the LS1/LS2. It's not perfect intentionally. Like a 'cammed car, it lopes off at-idle and smooths during acceleration. Normal.

Spaceme1117

They are about the same. The LS3 seems to have what I would call a "hitch" every now and again in the idle but is otherwise quite smooth. Some might mistake it for a misfire but this is normal. Compared to stock Gen II small blocks, the cams in LS engines are massive and this is compounded by the fact that the Gen II small blocks used a 1.5 rocker and the LS cars use a 1.7 rocker (1.8 in the LS7).

LS3 is a spectacular engine and would be awesome in a C3.

cv67

w/spaceme its smooth like any other stock motor. Some guys get too picky.