Hello, newby here. I have a 99 ws6 formula that has had long tube headers, highflow cats, ls6 intake, cam, and a few other goodies added by the previous owner.
I have older Pontiac's, including 2- 1972 455HO formula's, and have always enjoyed the crisp throttle response of a well tuned carb. With the 99', the response is good, but the return to idle seems slow. Is this normal? Can it be improved? I have the HP tuner software and interface, but have never looked into how much
control thas gives me.

Thanks

Welcome to the Source! Please post in the New Members Lounge so we can get to know you.

Not sure about LSx motors, but my LT-1 and my father's do that. Can always go with a 90mm throttle body, but I would bet you have one if you have the LS6 intake installed.

Matt

The PCM is programmed to keep the RPM elevated until the vehicle actually stops moving. I don't know the specifics of the LS1 PCM, but there should be a "follower" table that controls idle RPM during vehicle decel. Normally, the PCM opens the idle air control valve to let more air in as engine speed increases, so that the engine won't stall when the throttle blade snaps closed. The PCM will immediately cut fuel and retard timing to limit emissions. As the engine RPM drops, fuel flow will eventually be restarted, and the idle will be held high until the input from the vehicle speed sensor indicates the vehicle is no longer moving.

Thanks, I'm going to dig into the software, and try some small changes. The car does have that "snap" when I'm at a standstill, but when I am slowing down and push the clutch in the Idle does stay up till I am almost stopped. This is what Im interested in adjusting.

Henry

Please post back if you find a way to adjust the idle with clutch in and car moving. My '94 M6 could benefit from this, as well.