Idle's beautifully ... if I hold throttle to desired idle ... what's going on?

[Black LS1 T/A]

I've been screwing around with the VE (lower area), timing, cracker and idle tables and, though the car will idle nicely all the way down to 700 RPMs (big cam, supercharger, LS7 Stroker, 2Bar MAP Sensor, COS5, SD mode), if I take my foot completely off the pedal, it will dip on down below 400-500 RPM's and die. This difficulty occurred after switching to the 411 PCM. The 2002 PCM solved my RPM over-rev issues and no longer kills the transmission, but just getting it to crank initially was an issue. I have non-sensical values I had to place for Injector flow rates to get it to crank and run. It runs strong now. But, this idle thing ...

Any ideas what tables should I be massaging to overcome this?

It won't settle out at the Desired Idle values I give it. What is going on?

[joecar]

Post a log file and the tune file.

[Black LS1 T/A]

Two Logs with different Parms and a tune I just uploaded where I increased Base Spark down low.

[Black LS1 T/A]

Tune and 2 Scans

[joecar]

In your log 0224 I see several things:
- MAP is high at 86 kPa when TP is steady at 7.5%... what cam specs do you have (intdur/exhdur lsa adv)...?
- MAP flucuates while throttle is steady, I don't see IAC steps, but it is fluctuating too much.

What intake manifold do you have...? Do have any vacuum/air leaks...?

[Black LS1 T/A]

The TP is 0% when the pedal is not pressed. Remember, I have to hold the throttle open slightly, for it to stay cranked. That's why you see a Throttle angle. I think it may even be off-idle.

It idled the same place (800-900 RPMs, zero TP) on the 98 PCM and tune without cutting off.
I don't think I have any vacuum leaks

Also, remember, it wouldn't stay cranked the first time I loaded my tune after the PCM swap. I finally got it to stay cranked, but I can't take my foot off the accelerator pedal. Otherwise, it ran very strong.

I have the LS7 Intake Manifold.

Additional info: also, it cranks right up the first time, every time, cold or hot. But, I have to hold the throttle down slightly to maintain engine RPM at idle speed.

Competition Cam:
Gross Valve Lift: .623 .623
Duration @ .006 Tappet Lift: 289 305


Installed Specs:
Duration @ .050 239 254
Lobe Lift .367 .367
Lobe Separation 115

Thanks for your responses, joecar.

[joecar]

ok, we may have to go thru the idle tutorials...

[Black LS1 T/A]

OK. The car is not inspected yet, so I can't drive ... just idle in my driveway.
I'm getting a 10-day tag Monday, so I can take it to a tuner who says he is willing to tune with EFILive, and inspect the car so I can drive it. But, I need to time the 10-day tag where I can drive it a few days and still get it to him to iron out kinks before inspection. I was hoping I could get as much resolved as I can before I take it to him.

Every tuner around here uses the other package. I don't know why it's become entrenched in the market here. :(

[Black LS1 T/A]

I got it to idle without shutting off.
Adjusted quite a few idle parameters, so I can't say what by itself may have done it.
I also adjusted Injector Min Pulse width and Small Pulse adjust

[joecar]

Post the before and after tunes, lets have a look.

[Black LS1 T/A]

Here is the Calibration file with the adjustments I made.
(You have the "before" file in my post of the attachment before)

1. It cranks right away.
2. While cold, I have to hold the pedal down for it to stay in the idle area (about 800 to 875 RPM's).
3. Once temperature is stabilized, it idles fine, in or out of gear. (It's like a threshold it reaches and it idles at zero TP, not as if it is really cold)
4. Driving down the road, if I take my foot off the gas, around 30 MPH or so, it dips below idle point and I have to give it a little throttle.
5. If I come to a stop at a light, as I ease off the pedal, it finds idle and holds.

[joecar]

Looks like you may have to play with Throttle Follower and Throttle Cracker.

[Black LS1 T/A]

Looks like you may have to play with Throttle Follower and Throttle Cracker.

Thanks, Joe. You're the best