pcmhacking.net

Hi guy's, doing some tuning on my VR 5 litre Commodore manual running 12P.
Can anyone explain this paramater to me? "IAC - Idle MAP Threshold Vs Idle RPM"

I've got a problem im just starting to look into, i have'nt got a wideband yet which could make it hard.
The motor idles fine but then after the 20 second delay to idle mode it dies. The motor is quite modified but still standard stroke.

When looking around i come across this and I'm curious.

Appreciate any input

20 seconds is the default time to change from open loop fueling to idle fuel table, that may hold the answers. although that should be richening it so I wouldn't think that would kill it!

"IAC - Idle MAP Threshold Vs Idle RPM" is used for decel conditions to keep some air flowing as if the thottle was still open slightly. It helps emissions and helps the IAC to catch the engine when coming to a stop.

The catch is it can be triggered when idling on a high vacuum engine causing it to use open loop idle speed control (this is not fuel control), so long as your idle MAP is higher than values in this table it will go in to closed loop idle ok.

I closed loop idle at 70 kpa without touching that table i just changed iac max map setting im on my phone so cant tell you the exact name of constantnl.i had some stalling after time from map sensor error and ecu goijg into default map mode car would rev high then quit.maybe post a bin

Thanks, I will leave it alone then. When I'm on my computer I will post a log.
It idles at 75kpa. The idle spark is the same as the main table, idle afr is 13.2 and the main table afr is 13.5 at same point.
So I will keep logging and looking for now I wouldn't of thought that small change in afr would hurt it.

IAC Params - Maximum MAP load limit is what i change to suit idle kpa on 304 with a cam

Thanks mate I will look at that

IAC Params - Maximum MAP load limit is actually only used when there is no VSS and a code 24 is active.

ah good to know i guess thats why i needed it cause first few days it ran with no VSS LOL i guess its set ready for the next time the vss dies

I might be best to start a new thread but i've been logging my idle, I'm wondering if one of you guy's could take a look at it. It slowly dies untill i tap the throttle.
The vaccum dies as the AFR richens but im not sure if the vac is dropping off because of the afr change or vice versa.

The target idle is set high 1150rpm to try and help, once i get a steady idle and return to idle i will work on lowering it.

304 Holden V8 running Crane 288 solid with 10.5 compression. Im thinking of raising the compression aswell?