No Idle Compensation with AC On

[husseinholland]

I'm still trying to get the idle under control - the current issue besides the high idle is that the system does not adjust the idle to compensate for the AC compressor operating. The idle can drop to 600 or so when the compressor engages, before settling at about 800rpm. With the AC off, the idle is around 1100rpm.

I'm assuming the system uses the CANbus signals on E11 & E24 that come from the HVAC controller to also call for idle adjust? I don't have any way of replciating those signals in my '87 Fiat..

I'm trying to figure out if there is a way to use the E18 signal, or another input that will cause an idle increase when triggered?

Any suggestions?

EDIT: someone suggested using the PSP (E16) wire? So maybe a relay with the AC clutch signal to switch E16 to ground? Or does it need a resistance that the PSP switch would create in it's path to ground? Any thoughts on that?

As an aside to all this, if I have P0511 disabled in software, is that disabling the IACV or just the code?

[KTuner]

The PSP is ground at idle with steering wheel straight. You'll need to reference the manual for anything else.

P0511 is not meant to be disabled with an active IACV.

[husseinholland]

The PSP is ground at idle with steering wheel straight. You'll need to reference the manual for anything else.

P0511 is not meant to be disabled with an active IACV.

I disabled the P0511 code as it kept coming up, along with 0506. I can't get a good idle hot and cold with the IACV blocked off. It's either too high warm or too low cold. Surges when warm also. The only way I worked around it was to modify an IAVC as a manually adjustable valve, so I could open it for cold start & close it after warmup. That is no good as a long term solution.



I rechecked the diagnostic sequence & I don't have vBat when I get to step 15. So far, I've bought 2 IACV. I don't know where is a reliable source to look for one.



I'll research the PSP signal some more. Since I never connected E16 to a grounding source, this seems like it's a problem even if I get a working IACV, no?

[KTuner]

If you haven't properly tuned fueling you're likely to get surging. You can see what fuel trims are doing to help you verify that as a potential cause.

Your questions are beyond the scope of our software and hardware support.

[husseinholland]

If you haven't properly tuned fueling you're likely to get surging. You can see what fuel trims are doing to help you verify that as a potential cause.

Your questions are beyond the scope of our software and hardware support.

OK. Thank you for all you help, I'll post on K20.org.

[KTuner]

Hope you get it figured out.

[husseinholland]

Hope you get it figured out.

Indeed.

An idle related question - if I use the PSP signal wire as a (idle increase) trigger for when I have the AC on, should I set that parameter in Output Tasks? I can't find an outline for the appropriate way to use those for alternate purposes, or do they only work if you have the CAN-bus network or are they intended for bypassing those (CAN-bus) requests?



Researching articles on idle control, I also found this which may explain my jerky condition when cruising with tip-in/no almost no throttle:

So, if I cannot get the idle below 1100, are there adjustments that can be made to the system's preset fuel cut to prevent it coming into play in that rpm range?

[KTuner]

You don't have the ECU controlling AC output via the AC input selection currently?

Fuel Cut Settings are in the parameter list right there in your photo.

[husseinholland]

You don't have the ECU controlling AC output via the AC input selection currently?

I don't - I thought that without the CANbus AC control head, those would not work as intended. You're saying that I can use that to get the idle bump with AC on?

Fuel Cut Settings are in the parameter list right there in your photo.

Yeah, sorry about that one - I realized after I added that, that there is a Fuel Cut parameter section. I'll play around with raising the base cut off

[KTuner]

Correct. Choosing an AC Input to be the activation switch for the pressure controlled output, as a regular working AC system would, allows the ECU to idle up and activate the AC Output to properly control the AC clutch.