CL Idle Not Engaging with AC Idle Up on

[smandzak]

I've been having a problem with closed loop idle not engaging since I enabled the Air Conditioning Idle Up.

As background, previously I didn't have an input tied into the AC and closed loop would always reliably engage. Since I needed an idle bump this summer with AC on I finally got it hooked up and configured. Unfortunately CL idle tends to not engage unless AC is on.

Today I grabbed a data log of a cold start, and you can see that even though it is 400 rpm over target the IAC PW never changed. I shut off the engine, switched the AC Idle off, restarted and closed loop smoothly brought the engine to target. Enabled AC idle again (engine off, etc) and I was back to a high idle with no reaction.

Drove it home that way and I figured out that I could temporarily trigger CL idle at each light if I toggled the AC On and right back off. But as soon as I accelerated at the next stop it would be stuck at the initial IAC PW value again. So it seems this AC code has some interaction in the problem.

Any ideas?

P.S. Any idea what the meaning of "Idle-up CL load Allowance (%)" in the Air Conditioning Idle-Up screen? Engine states and all other screens for closed loop don't seem to define a load cutoff, so no idea how this is used.

[smandzak]

Just to visualize the difference, here is the graph of the subsequent restart after disabling AC Idle Up (no problem).

[mill383]

smandzak,

Are you using the "Discrete Switched12V IN" as the A/C request? I am on my setup, and found out that there is an inversion with the weak pull-down. When it is set to ON its really OFF, etc. I didn't find the thread on it until I already trouble shot the issue, and soldered a pull-to-ground 10K resistor inside my MS3Pro. Prior to doing this, I had completely indeterminate activation of the system. Its squirreled away in the "Special Options" tab, under "Canbus/Test Modes".

Not sure this is a contributor, to this problem.

http://www.msextra.com/forums/viewtopic ... 31&t=69005

Anyways, mine hasn't repeated yet. Have had solid CL IDLE after every start. Probably a dozen starts since my event. I'm just waiting for it to repeat, and maybe bet some data on the SD card or laptop. We'll see...

But as soon as I accelerated at the next stop it would be stuck at the initial IAC PW value again.

I need to try that on my car, next time I'm out. This problem maybe hasn't manifested as much with my setup, because I leave it in "auto" mode and the head unit cycles the request on-off as needed. I'll drive around with it off, and see if it default and sticks at Initial IAC PW position. Hmmm, and the plot thickens....

Dave

[smandzak]

Just checked and I'm using 'Digital Switched In 1'.

It always seems to recognize the A/C signal OK (for example the rad fan behavior is always matching).

I also can't understand in the code how a indeterminate A/C signal would confuse CL idle. Maybe the target RPM would bounce around between the A/C on and off setting, but not stick at 1300rpm or something... Once we get back to warm weather I can throw a resistor on to try it, not like it will hurt anything

Anyway, thanks for the suggestion, I appreciate it!