Loss of Idle control after A/C engagement.

[muttley383]

Hi, looking for some help with the idle tuning when the A/C clutch is engaged.

Engine idles ok without A/C and keeps control after a stumble after the thermo fans switch on.
When the A/C clutch is engaged idle mixtures go initially lean then recover, engine idles for approx 8 seconds then it looses idle control with a massive lean out until it stalls. Turn off A/C and restart the engine and it controls ok.

Attached is a log of what is happening. @ 2.19 A/C is engaged, @ 2.27 loss of control causing excessive leanout and stalling.
What I did notice in the log is that there is decel enrichment active, is this normal?
Can anyone give some info on what parameters to look at to enable control of the idle when the A/C is engaged?

Basic engine specs:
383 cuin stroker holden V8
c.o.m.e CSBH222 camshaft
Torque Power Dual plane hi-rise manifold.

Using OSE_12PV110.xdf.

[Holden202T]

i can't really explain that one, first i was thinking the 30kpa area of your ve map might have been lean but its not that i don't think, it seems to get back to rich enough idle then leans out again before stalling!

none of the main stuff like coolant temp or anything like that are really changing numbers at all other than the afr and the rpms!

[VL400]

I would firstly look at "IAC Params - Initial additional A/C steps" as its adding over 40 steps when the A/C kicks in - RPM kicks up around 400RPM. Also if you can post your cal when posting logs it can also help diagnose it too.

I think the decel enleanment your seeing is part of the manifold fuel calc. It estimates the amount of fuel thats condensed on the manifold walls so when the RPM increases sharply this fuel gets drawn in - there is a AE and DE component for the manifold fuel calc. The ECU compensates for a rise in RPM (and reduction in manifold fuel) by invoking DE to lean off the injector PW and then decay back to 0 DE.

To disable the DE part of the manifold fuel calc and test this theory, make "Decel Enleanment Param - DE delta fuel threshold" = 255

If that stops the DE can then play around with "Transient - DE Gain Vs Delta manifold fuel" and "Manifold Fuel Param - RPM gain factor for MANFUEL calc" so it does not lean out as much.

[Doctor Bob]

check the current draw on the ac clutch & fans as well

[vn5000]

I would also check the fuel press when the a/c is turned on .