Ok,
I am about to go back to the track, I have been looking at the vacuum lines and cannot find one. Anyone else know these issues from the past?

Runs hard, just readjusted roller rockers. I just am tired of dropping rpms on decelleration. I am thinking I may have to check my new throttle body for IAC counts etc. but before I download a new freescan version and do all that I wanted to see if that even is in the ballpark of what it could be. It starts up and idles perfectly, it is only after accelerating for a bit that it dies. It doesnt die all the way either, drops to 500 and I can keep it running with a little gas. It will just sit at 500rpms too for a while... last time at the track though it died after a burnout and htat was pretty embarrassing.

 

try opening up your throttle body blades with the set screw. It's pretty common to have to open them up a touch to get enough air into the motor.

 

Mine would do that too once in awile. It got better when I changed the set screw and changed PCM to idle at 850.

 

Any luck solving this?
I am having kind of the same problem with a fresh rebuilt 355 LE2 97 LT1.
Mine Idles fine and runs hard. It will almost stall when coming to a stop at a stoplight. RPMs will drop to 500-600 and after a short it will go back to the programmed 850 RPM
I have tried via programming with no luck altering the IAC/MPH follower table.
Yesterday I opened the throttle blades a bit ( approx 1/2 turn) and am under the impression it got much better. Still have not had a chance to drive it much.

I am using a HOLLEY 58 MM TB and it is different from the OEM TB. The difference being that it does not have a small hole supplying idle air directly to the plenum regardless of IAC pintle position. That might be the reason...

 

The IAC motor should start to open up (increase counts) as the speed goes up. It does that to prevent stalling when the throttle blades suddenly close on decel. Not sure if that can be adjusted in the tune, but I would think it could be. Both of you obviously have custom tunes.... check with the tuner.

 

I have heard of tuning the IAC to help with idle, I think the one you'd be looking for is in the constants called Default minimum IAC Keep Alive.

 

In Tunercat it is the "Throttle Follower IAC Offset Vs MPH" table. It goes something like...

MPH | Steps
0.....|.....3
4.....|.....4
8.....|.....8
12...|.....12
16...|.....16
20...|.....20
24...|.....20
28...|.....20
32...|.....20
36...|.....20
40...|.....20
44...|.....20
48...|.....20
52...|.....20
56...|.....20
60...|.....20
64...|.....20


In my M6 computer the programmed RPM is only 850 at 32*c. The higher the temp the more the RPM goes down. All the way to 625RPM at 92*c. Don't know if that helps anyone.

 

That is tha table I edited adding more steps to the lower values only and leaving the higher MPH values alone. Something like this:

MPH / STEPS
0..../....25
4..../....15
8..../....10
12.../....12

There were no noticeable changes.
I have my Idle set up to 850 RPM all the way from 111 to 240 Deg F

Mystery Bird:

I use LT1 Edit or my programming and can't fid that constant. Is it availiable in Tunercat?

 

Did you mess with DFCO at all? Maybe raise the MPH enable value.

The throttle follower table is probably more useful to manuals because pushing in the clutch and letting off the throttle can stall the engine if the follower is set too low. Also can potentially help with gear changes.

 

No, I have not touched the DFCO tables. This is happening in the M6. It happens when I am coming to a stop at a stop light at very low speeds. I only tries to stall the exact moment you come to a complete stop. It does not stall during rolling, even at very low speeds. I think the HOLLEY throttle body is the cause.

 

Your probably right there.. I still have the OEM TB. Have you logged during the problem? is the IAC maxing out at some point?

 

[QUOTE=
I use LT1 Edit or my programming and can't fid that constant. Is it availiable in Tunercat?[/QUOTE]

Yes that table is in Tunercat.

Did you also set the TPS voltage with the new TB? I have the Holley 52mm and only had to change it slightly. Also, had the split BLM's which was fixed as well when I adjusted the set screw and programmed the 850 idle.