Help!!! Cold start with A/C on sucks!
Thread Starter
Joined: Nov 2001
Posts: 8,246
Likes: 34
From: Victoria, TX
Help!!! Cold start with A/C on sucks! A little background on my car.
346ci, M6, AFR 205 heads, 231/234 112LSA cam, Kooks headers with cats, FAST 90, Nick Williams TB, 85mm SLP MAF.
I've done most of the fine tuning. Warm idle and driveability is very good. Here's what I've done:
Base idle 34 degrees (good IAC counts with this timing)
Zeroed out the startup timing retard tables
Zeroed out the ECT timing retard tables
Hi/Low Octane table with 34 degrees of timing at lower rpm and load.
Speed Density tune with VE tables running -2 degrees S Trims max
Scaled MAF to keep L-Trims slightly negative.
Base RAF nice and high (12 when fully warm)
Parked Idle Airflow up 10%
Dynamic airflow, desired idle airflow and MAF airflow all match with the A/C on when car is warm.
OK, here's the deal. I feel I've done everything right, and my car starts fine when dead cold as long as the AC is turned off. The car starts right up and idles nice. But if I try to start it when it's dead cold with the AC on, the motor will sputter and die. I have to feather the throttle to keep it from dying. Turning off the AC cures the problem, but I'd rather not sweat as soon as I jump in the car in the August heat. HELP!!!
346ci, M6, AFR 205 heads, 231/234 112LSA cam, Kooks headers with cats, FAST 90, Nick Williams TB, 85mm SLP MAF.
I've done most of the fine tuning. Warm idle and driveability is very good. Here's what I've done:
Base idle 34 degrees (good IAC counts with this timing)
Zeroed out the startup timing retard tables
Zeroed out the ECT timing retard tables
Hi/Low Octane table with 34 degrees of timing at lower rpm and load.
Speed Density tune with VE tables running -2 degrees S Trims max
Scaled MAF to keep L-Trims slightly negative.
Base RAF nice and high (12 when fully warm)
Parked Idle Airflow up 10%
Dynamic airflow, desired idle airflow and MAF airflow all match with the A/C on when car is warm.
OK, here's the deal. I feel I've done everything right, and my car starts fine when dead cold as long as the AC is turned off. The car starts right up and idles nice. But if I try to start it when it's dead cold with the AC on, the motor will sputter and die. I have to feather the throttle to keep it from dying. Turning off the AC cures the problem, but I'd rather not sweat as soon as I jump in the car in the August heat. HELP!!!
__________________
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
Iac
Originally Posted by Patrick G
A little background on my car.
346ci, M6, AFR 205 heads, 231/234 112LSA cam, Kooks headers with cats, FAST 90, Nick Williams TB, 85mm SLP MAF.
I've done most of the fine tuning. Warm idle and driveability is very good. Here's what I've done:
Base idle 34 degrees (good IAC counts with this timing)
Zeroed out the startup timing retard tables
Zeroed out the ECT timing retard tables
Hi/Low Octane table with 34 degrees of timing at lower rpm and load.
Speed Density tune with VE tables running -2 degrees S Trims max
Scaled MAF to keep L-Trims slightly negative.
Base RAF nice and high (12 when fully warm)
Parked Idle Airflow up 10%
Dynamic airflow, desired idle airflow and MAF airflow all match with the A/C on when car is warm.
OK, here's the deal. I feel I've done everything right, and my car starts fine when dead cold as long as the AC is turned off. The car starts right up and idles nice. But if I try to start it when it's dead cold with the AC on, the motor will sputter and die. I have to feather the throttle to keep it from dying. Turning off the AC cures the problem, but I'd rather not sweat as soon as I jump in the car in the August heat. HELP!!!
346ci, M6, AFR 205 heads, 231/234 112LSA cam, Kooks headers with cats, FAST 90, Nick Williams TB, 85mm SLP MAF.
I've done most of the fine tuning. Warm idle and driveability is very good. Here's what I've done:
Base idle 34 degrees (good IAC counts with this timing)
Zeroed out the startup timing retard tables
Zeroed out the ECT timing retard tables
Hi/Low Octane table with 34 degrees of timing at lower rpm and load.
Speed Density tune with VE tables running -2 degrees S Trims max
Scaled MAF to keep L-Trims slightly negative.
Base RAF nice and high (12 when fully warm)
Parked Idle Airflow up 10%
Dynamic airflow, desired idle airflow and MAF airflow all match with the A/C on when car is warm.
OK, here's the deal. I feel I've done everything right, and my car starts fine when dead cold as long as the AC is turned off. The car starts right up and idles nice. But if I try to start it when it's dead cold with the AC on, the motor will sputter and die. I have to feather the throttle to keep it from dying. Turning off the AC cures the problem, but I'd rather not sweat as soon as I jump in the car in the August heat. HELP!!!
What are your IAC counts? If you have too much or too little then either the car will surge or will die when the A/C is turned on. After tuning cars I will usually sit there with the car at idle and cycle the AC on and off so the PCM will learn, At first the idle will drop then rise to the correct setting, after doing this for a few times it will not drop at all and the idle will remain stable.....
Thread Starter
Joined: Nov 2001
Posts: 8,246
Likes: 34
From: Victoria, TX
Originally Posted by moehorsepower
What are your IAC counts? If you have too much or too little then either the car will surge or will die when the A/C is turned on. After tuning cars I will usually sit there with the car at idle and cycle the AC on and off so the PCM will learn, At first the idle will drop then rise to the correct setting, after doing this for a few times it will not drop at all and the idle will remain stable.....
Does the "Desired IAC Area Max" figure have anything to do with it? Mine was originally 84. Now it's at 200. Do I want it to be higher or lower?
Patrick this is a problem that not only you have. I am in the process of trying to figure it out myself. I have tried almost everything I can think of but I think I am onto something. I will need a few more days to double check and see if things are going to work. If not, I'll just make sure the a/c is off when I start the car. A little sacrifice I guess.
"All Motor 9 Second club member"
iTrader: (60)
Joined: Nov 2001
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From: On the Bumper!
Patrick- Go to Eng-idle A/F- Cooling fan air in HPTuners and try raising the airflow parameters. It is supposed allow additional air to maintain the load of the drawn current of the cooling fans which come on when the A/C compressor is commanded to activate. On that same tab to the right side there are a few options to change A/C load limits. I'm not totally familiar with the exact issue you have , but I have bumped these settings and my car is more stable with the A/C on than off.
I was very conservative on these parameters since I didn't have too much of an A/C load issue and I was battling other minor issues at the same time. I can send you my bin file if you like. Good luck and keep us posted. It doesn't sound like your alone on this one. I bet these tables will correct it though. I'm running a 244/244 612/612 cam and it doesn't flinch with the a/c on.
I was very conservative on these parameters since I didn't have too much of an A/C load issue and I was battling other minor issues at the same time. I can send you my bin file if you like. Good luck and keep us posted. It doesn't sound like your alone on this one. I bet these tables will correct it though. I'm running a 244/244 612/612 cam and it doesn't flinch with the a/c on.
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Thread Starter
Joined: Nov 2001
Posts: 8,246
Likes: 34
From: Victoria, TX
Originally Posted by TXCAMSS
Patrick- Go to Eng-idle A/F- Cooling fan air in HPTuners and try raising the airflow parameters. It is supposed allow additional air to maintain the load of the drawn current of the cooling fans which come on when the A/C compressor is commanded to activate. On that same tab to the right side there are a few options to change A/C load limits. I'm not totally familiar with the exact issue you have , but I have bumped these settings and my car is more stable with the A/C on than off.
I was very conservative on these parameters since I didn't have too much of an A/C load issue and I was battling other minor issues at the same time. I can send you my bin file if you like. Good luck and keep us posted. It doesn't sound like your alone on this one. I bet these tables will correct it though. I'm running a 244/244 612/612 cam and it doesn't flinch with the a/c on.
I was very conservative on these parameters since I didn't have too much of an A/C load issue and I was battling other minor issues at the same time. I can send you my bin file if you like. Good luck and keep us posted. It doesn't sound like your alone on this one. I bet these tables will correct it though. I'm running a 244/244 612/612 cam and it doesn't flinch with the a/c on.
patrick@guerragroup.com
Thanks in advance.
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