AC Idle Help - Desired Idle Rising

[BuckNasty92]

Good morning all. Been searching, playing with parameters and talking to people I know with no luck.

Run down on vehicle: It's a 2001 Silverado P01, 5.3, e-fans from 2005 denali, 3200 stall, 80e, s475 with SS2 Cam. I recently put AC system back in it (cycling style without pressure sensor) and is working really well.

Truck idles and drives without issue with AC Off In Gear or P/N. The issue I'm having is when sitting for about 10-30 seconds with ac on and in gear, the desired idle PID will start to rise from my set 850 up to around 925. It won't come back down no matter how long I wait or even if I shift to P/N. The only way for it to come back down is to turn the AC off and let it idle for a few seconds.

It's hard for me to dial in my STIT's because of how it's reacting and even when I tried to get them wrangled in, the truck feels like it's pushing pretty hard forward on the brakes like the converter isn't loose enough no matter what the desired idle is set to (850 vs 925)

In the attached log, you'll see towards the end where it rises and I shut the AC off for it to reset. I have a feeling this is something simple I've overlooked for about 2 weeks now but need some help so I can get this thing driving right. Thank you.

AC Idle Base 1.hpt
New Base AC Tune.hpl

[kevin87turbot]

You can reduce the AC Offset Max under the Idle airflow adapts for both P/N and In Gear as well.

[BuckNasty92]

I've messed with them a bit and I believe "widened" the margins. I set it to -3.00 g/s min ac offset and 3.00 g/s max ac offset in both in gear and off gear. The only time I got the RPM not to rise was when I actually set all off these to "0" but I know that can't be a permanent fix.

[kevin87turbot]

If you don't want any additional RPM rise when the AC comes on, then you can "0" the Max AC airflow adapts. You can also disable the throttle cracker tables by increasing the Enable Speed to a high value.

[BuckNasty92]

The amount of RPM rise in the tune is okay (800ac off/850 ac on) but it will then rise an additional 75rpm above what?s programmed to be

[sevinn]

Had this issue on a truck previously and never got to resolve it because the owner sold the truck. Definitely curious.

[BuckNasty92]

Had this issue on a truck previously and never got to resolve it because the owner sold the truck. Definitely curious.

What was year and model?

[sevinn]

03 silverado ss with a p59

[village_idiot]

As long as it still idles good, and transitions in and out of idle fine, zero out the AC airflow adders, and leave it. Maybe enable idle bump tq spark to help with the load transition. I am surprised your idle is okay with 31 degrees of timing advance

[BuckNasty92]

I'll play around with those a bit more and let you know how it goes. Would be nice just to avoid dealing with it. I'll post back on here my results.

[sevinn]

In my case it only started after enabling efans.

[BuckNasty92]

In my case it only started after enabling efans.

Really? I had LS1 fans originally but switched to fans from a 2005 Denali. First time I ever used the cooling fan adder parameter. That might be my next thing to look at.

[sevinn]

Really? I had LS1 fans originally but switched to fans from a 2005 Denali. First time I ever used the cooling fan adder parameter. That might be my next thing to look at.

Yes sir, I went to tune it after he bought the fans from an unknown junkyard truck and the on3 fan harness and ran out of time troubleshooting the issue, but same as you. ID just raises to 950 and then they sold the truck off the lot before I had time to go back and try anymore.

[BuckNasty92]

Yes sir, I went to tune it after he bought the fans from an unknown junkyard truck and the on3 fan harness and ran out of time troubleshooting the issue, but same as you. ID just raises to 950 and then they sold the truck off the lot before I had time to go back and try anymore.

So after you mentioned the fans, I started searching and turned up a handful of posts on e-fan conversion issues. The one I found most similar was a guys fans were constantly running the low setting which mine was doing too. I didn?t connect it to retuning the truck for AC. This was fixed by turning pin 33 from auto recirculation to fan control 2. This seems to have fixed my rising idle problem as well as my cooling fan always on.

Now I?m not sure if it was switching what pin 33 does or if it was changing the AC type fitted to ?Cycling? instead of ?Analog Cycling? which was also recommended in that thread

[sevinn]

So after you mentioned the fans, I started searching and turned up a handful of posts on e-fan conversion issues. The one I found most similar was a guys fans were constantly running the low setting which mine was doing too. I didn?t connect it to retuning the truck for AC. This was fixed by turning pin 33 from auto recirculation to fan control 2. This seems to have fixed my rising idle problem as well as my cooling fan always on.

Now I?m not sure if it was switching what pin 33 does or if it was changing the AC type fitted to ?Cycling? instead of ?Analog Cycling? which was also recommended in that thread

I had tried changing the pin 33 type when I was messing with it, but maybe not. Been almost 2 years now. If I come across it again I'll keep it in mind. Glad I could point you in the right direction I guess lol