Idle with Air Condition on. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**Accelo** · 03-19-2022, 07:45 PM

I just charged the Vintage Air I have installed on my LS1 motor in my C10 truck. The LS1 has a BTR Stage II truck cam installed. It idles fine in or out of gear without the air on. However, with the air on the motor surges and struggles to keep running when ever the pump kicks in.
Background is the motor is stock except for the headers and cam. ECM has not been tuned nor has the motor done any driving except for idling in the shop.

Since the Vintage Air is not connected to the ECM in any way I have to assume the idle is controlled by the idle air control. Doesn't seem to controlling the idle with the air-conditioning running. Maybe it's just chasing it's tail.

I'm thing I shouldn't worry about this till I get some miles on it and the computer has had time to learn.
What is everyone's take on this? I am all ears. This is my first LSx swap.

ls1nova71 · 03-20-2022, 10:56 AM

If you've swapped cams, a tune is mandatory. If the PCM isn't chasing it's tail, you will be by trying to drive a cammed engine with a stock tune!

That said, the IAC should be fully capable of controlling any extra load placed on the engine by the AC compressor. Some people say you need the PCM to know when the AC is on, but in my experience, which is a lot of miles, it doesn't matter.

**AussieinNC** · 03-20-2022, 04:34 PM

Ditto to what ls1nova71 said.

The ECM must know when the air is turned on and compressor is cycling. The ECM will then know to increase the idle and timing etc to compensate for the load.

Even the earlier version DBW systems had the ECM feedback from AC controls so it could compensate.

Plus, any cam change should be accompanied by an ECM tuned to suit the installation.

Does the vehicle still have CATS in place? O2 sensors?

**Accelo** · 03-20-2022, 04:42 PM

Quote:

Originally Posted by AussieinNC

Ditto to what ls1nova71 said.

Does the vehicle still have CATS in place? O2 sensors?
:

No CATS but I does have the two forward 02 sensors.

This is a fairly mild cam as far as they go. I am told it will work with a stock converter. It idles in gear fine, that is without the AIR on. I plan on starting it again today and checking the scan tool for IAC function.
I was planning to get a tune but was attempting to get any obvious issue dealt with first. Currently the motor starts immediately and idles fine without the AIR on.

**CarlsLQ9SS** · 03-25-2022, 09:15 PM

Any aftermarket cam even if its a mild grind requires proper tuning. Being that it is a mild cam it may idle OK without a tune but its not as efficient in lower RPMs as a stock cam. So the slightest load on the engine will cause it to struggle to idle. I done a swap on a 65 GMC with a cam and old air products ac system, and it wouldn't idle with the ac on until I had it tuned. I didn't have the ac ran through the computer either and it worked fine. I hope this helps and you get it lined out.

**Accelo** · 03-28-2022, 10:59 PM

CarlsLQ9SS
Thank you for the tip. Having never gone down this route it is sometimes difficult to figure out the correct path.

kglowacky · 04-02-2022, 07:23 PM

I am getting ready to complete my ac system also , When I had my harness re worked he left the AC wire in the harness. My question is does anyone know how or what this one wire would connect to in the system? Does it need neg or positive power going to it when you turn on the ac?

03-19-2022, 07:45 PM	#1
Accelo Senior Member Join Date: Mar 2015 Location: washington Posts: 2,295	Idle with Air Condition on. I just charged the Vintage Air I have installed on my LS1 motor in my C10 truck. The LS1 has a BTR Stage II truck cam installed. It idles fine in or out of gear without the air on. However, with the air on the motor surges and struggles to keep running when ever the pump kicks in. Background is the motor is stock except for the headers and cam. ECM has not been tuned nor has the motor done any driving except for idling in the shop. Since the Vintage Air is not connected to the ECM in any way I have to assume the idle is controlled by the idle air control. Doesn't seem to controlling the idle with the air-conditioning running. Maybe it's just chasing it's tail. I'm thing I shouldn't worry about this till I get some miles on it and the computer has had time to learn. What is everyone's take on this? I am all ears. This is my first LSx swap.

03-20-2022, 10:56 AM	#2
ls1nova71 Registered User Join Date: Dec 2009 Location: Independence Mo Posts: 4,118	Re: Idle with Air Condition on. If you've swapped cams, a tune is mandatory. If the PCM isn't chasing it's tail, you will be by trying to drive a cammed engine with a stock tune! That said, the IAC should be fully capable of controlling any extra load placed on the engine by the AC compressor. Some people say you need the PCM to know when the AC is on, but in my experience, which is a lot of miles, it doesn't matter. __________________ My '72 short bed build. http://www.ls1tech.com/forums/conver...6-0-4l80e.html 5.3 swap into my RUSTY '71 C10 http://ls1tech.com/forums/conversion...71-c-10-a.html

03-20-2022, 04:34 PM	#3
AussieinNC Moderator Join Date: Jun 2017 Location: Cherryville, NC Posts: 2,204	Re: Idle with Air Condition on. Ditto to what ls1nova71 said. The ECM must know when the air is turned on and compressor is cycling. The ECM will then know to increase the idle and timing etc to compensate for the load. Even the earlier version DBW systems had the ECM feedback from AC controls so it could compensate. Plus, any cam change should be accompanied by an ECM tuned to suit the installation. Does the vehicle still have CATS in place? O2 sensors? __________________ Family and country before all others... 2006 Chevy Silverado (Daily Driver) 2012 Chevy Equinox

03-25-2022, 09:15 PM	#5
CarlsLQ9SS Senior Member Join Date: Aug 2018 Location: London, Ky Posts: 1,162	Re: Idle with Air Condition on. Any aftermarket cam even if its a mild grind requires proper tuning. Being that it is a mild cam it may idle OK without a tune but its not as efficient in lower RPMs as a stock cam. So the slightest load on the engine will cause it to struggle to idle. I done a swap on a 65 GMC with a cam and old air products ac system, and it wouldn't idle with the ac on until I had it tuned. I didn't have the ac ran through the computer either and it worked fine. I hope this helps and you get it lined out. __________________ Carl 1971 GMC short bed, (Henry) Options I've added, tilt, ac, 8k tach, Electric speedometer conversion for LS swap, 6.0 with 823 heads and BTR stage 4 truck cam, 4L80e, posi with 3.73 rear end, Power steering and power brakes Lowered 5/7. Frame up build.

03-28-2022, 10:59 PM	#6
Accelo Senior Member Join Date: Mar 2015 Location: washington Posts: 2,295	Re: Idle with Air Condition on. CarlsLQ9SS Thank you for the tip. Having never gone down this route it is sometimes difficult to figure out the correct path.

04-02-2022, 07:23 PM	#7
kglowacky Registered User Join Date: Mar 2020 Location: The Woodlands,Tx Posts: 588	Re: Idle with Air Condition on. I am getting ready to complete my ac system also , When I had my harness re worked he left the AC wire in the harness. My question is does anyone know how or what this one wire would connect to in the system? Does it need neg or positive power going to it when you turn on the ac?



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