Hi guys, not sure really where I should post this but here I go. So about a month ago I bought a 98 ss with a decent amount of mods. Its cam'd has ls6 heads, ls6 intake, not sure if the rockers, lifters, and pushrods are stock, full length American racing headers to a catless y and magnaflow cat back. Its been tuned at least I was told it had. I had a couple of questions for you guys with much more experience with modded ls cars. My car idles at about 1100-1200. Doesn't surge just idles. Now if I let the clutch out to drop the rpms a little and push the clutch back in the car will stumble and rev a little then go back to idle. Is this normal? Also the car runs rich all the time. Even at wot. Any help would be awesome. I just don't think that idle is normal for a cammed car.

 

The stock idle speed for an M6 LS1 F-body is 800rpm once fully warmed up. However you said the car has been tuned, and changes (increases) to idle speed are pretty common for cammed applications. Just how high the idle needs to be will depend on quality of the tune and size of the cam. 1100-1200 is a bit on the high side unless it's a pretty big cam, but the stock tach isn't all that accurate. Mine have always been off anywhere from 50-150rpm at idle (usually reading high), so without a scanner you can't really know what the exact idle speed is. But higher than stock is certainly typical for a cammed car with a tune.

You would need to get a scanner and see what the commanded idle speed is to know if it's actually idling too high or not. However, if the idle is more than ~150rpm above the commanded speed then you'd be getting a P0507 code and a MIL, unless someone disabled P0507 with the tune, however this is doubtful. More than likely, the idle was just set high during the tune.

If the idle is stable and not surging (as you've mentioned), then this is further indication that it's following its commanded preset.

 

If you use an OBDII scan tool, does the rpm on the scan tool match the rpm on the gauge?

I believe the stock gauge is a bit off, perhaps its actually running correct but the few hundred rpm that the gauge is off is messing with your mind.

 

Are those rpms when cold or fully warmed up after 15 minutes? Shuould be closer to 650-700rpm. Maybe someone messed with some sensors, or O2's making it stay in a high idle loop all the time.

 

Rubber boot for the PCV line at the throttle body
is on borrowed time and have seen them torn /
cracked, causing high idle.

As for "always rich", I have to wonder how you know
what you think you know, or if. Many ways to get
there but a lot of people misinterpret smells and soot,
let alone causes.

 

As I posted above, the stock idle is set at 800rpm from the factory for every M6 LS1 F-body, so 650-700rpm would not have been the case even with a stock tune.

The OP has an aftermarket cam and tuning, so what's most likely is that the idle speed was raised further during the tune. If the car was actually idling at 11-1200rpm with a factory commanded speed of 800rpm still in place, then he'd be getting a P0507 code for high idle.

The tach is probably off a bit, as are most of them. And the idle speed has probably been raised a bit, via the tune, due to the aftermarket cam which is also typical.

No point in trying to diagnose any problem when we don't even know what the commanded idle speed has been set to during the tune, or how far off the tach is - and both of those things would require an OBD scanner to verify.