Problem when A/c is on.
Thread Starter
4th Gear
Joined: Apr 2017
Posts: 4
Likes: 0
Problem when A/c is on.
Hello everyone.
i have a 1996 LT-4, 6 speed.
Every time i'm running the A/c, (which is often here in AZ), I notice that the RPM's are low at idle, and it drops fast between shifts.
At idle, its probably around 600, i'm surprised the car stays on. And when i push in the clutch to shift, they drop very quick as if i put it in neutral making the car jump a bit when i pull out the clutch in the next gear.
As soon as i turn off the a/c, the idle rpm is back up at 900-1000 and the shifts are perfect and smooth.
i know it an old car and i know that the a/c gets it power from the engine, but is this normal? Or can this be fixed somehow? And also, what causes this?
Thanks for the help!
i have a 1996 LT-4, 6 speed.
Every time i'm running the A/c, (which is often here in AZ), I notice that the RPM's are low at idle, and it drops fast between shifts.
At idle, its probably around 600, i'm surprised the car stays on. And when i push in the clutch to shift, they drop very quick as if i put it in neutral making the car jump a bit when i pull out the clutch in the next gear.
As soon as i turn off the a/c, the idle rpm is back up at 900-1000 and the shifts are perfect and smooth.
i know it an old car and i know that the a/c gets it power from the engine, but is this normal? Or can this be fixed somehow? And also, what causes this?
Thanks for the help!
Safety Car
Joined: Aug 2009
Posts: 3,745
Likes: 275
From: Melbourne, Victoria, Australia
Hello everyone.
i have a 1996 LT-4, 6 speed.
Every time i'm running the A/c, (which is often here in AZ), I notice that the RPM's are low at idle, and it drops fast between shifts.
At idle, its probably around 600, i'm surprised the car stays on. And when i push in the clutch to shift, they drop very quick as if i put it in neutral making the car jump a bit when i pull out the clutch in the next gear.
As soon as i turn off the a/c, the idle rpm is back up at 900-1000 and the shifts are perfect and smooth.
i know it an old car and i know that the a/c gets it power from the engine, but is this normal? Or can this be fixed somehow? And also, what causes this?
Thanks for the help!
i have a 1996 LT-4, 6 speed.
Every time i'm running the A/c, (which is often here in AZ), I notice that the RPM's are low at idle, and it drops fast between shifts.
At idle, its probably around 600, i'm surprised the car stays on. And when i push in the clutch to shift, they drop very quick as if i put it in neutral making the car jump a bit when i pull out the clutch in the next gear.
As soon as i turn off the a/c, the idle rpm is back up at 900-1000 and the shifts are perfect and smooth.
i know it an old car and i know that the a/c gets it power from the engine, but is this normal? Or can this be fixed somehow? And also, what causes this?
Thanks for the help!
The a/c harness connector to a/c usually has a diode across it, that should be there and the ecm sees the 12 volts a/c on.
Adjusts idle speed to compensate for the a/c drag.
600 rpm sounds normal for early c4s, I doubt the 96 would be higher.
Perhaps someone will chime in and say what the correct 96 idle speed should be.
Melting Slicks
Joined: May 2014
Posts: 2,888
Likes: 590
From: New Port Richey FL
Hi imam not familiar with the 96.. so take that in mind.
The a/c harness connector to a/c usually has a diode across it, that should be there and the ecm sees the 12 volts a/c on.
Adjusts idle speed to compensate for the a/c drag.
600 rpm sounds normal for early c4s, I doubt the 96 would be higher.
Perhaps someone will chime in and say what the correct 96 idle speed should be.
The a/c harness connector to a/c usually has a diode across it, that should be there and the ecm sees the 12 volts a/c on.
Adjusts idle speed to compensate for the a/c drag.
600 rpm sounds normal for early c4s, I doubt the 96 would be higher.
Perhaps someone will chime in and say what the correct 96 idle speed should be.
Last edited by s carter; Apr 17, 2017 at 09:42 PM.
Melting Slicks
Joined: Jan 2008
Posts: 2,054
Likes: 120
From: AZ
600 seems low, unless it were an in-gear automatic.
Does the '96 have a solenoid to kick up the idle due to increased load from the A/C?
Last edited by whalepirot; Apr 17, 2017 at 09:18 PM.
Melting Slicks
Joined: May 2014
Posts: 2,888
Likes: 590
From: New Port Richey FL
Not a Stand alone Solenoid like old cars pre-FI it is handled by the IAC valve should kick it up a notch
Last edited by s carter; Apr 17, 2017 at 09:35 PM.
Team Owner
Joined: Jul 2004
Posts: 28,376
Likes: 3,260
From: Hartford WI
As to the idle speed, is there a way to hook up a scanner to see what the desired idle is? See whether the IAC is trying to compensate and whether the RPM you report is accurate per the ECM.
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