Ac Cutting In & Out At Idle

[edbro]

I cleaned the IACV a couple of days ago, reset the computer and drove it around for about 15 miles. All was good.

For 2 days now when I go to start it, it will not idle cold. After warming up it is fine. But, my problem now is that when at idle with the AC on, the idle drops to 500 and either the AC stops working or the idle will surge fairly rapidly between 500-1000 with the AC turning off and on. I drove about 40 miles around town yesterday. Mostly it was surging but towards the end, I noticed that the idle was smooth at 500 but the AC was blowing warm while at idle. If I turn the AC off the car idles around 750 fairly smoothly. Today, it was cutting off and on again. With the hood open I can see the AC clutch stopping and starting. If I rev the engine just a bit, the AC works fine.

Any ideas?

[wwest]

I cleaned the IACV a couple of days ago, reset the computer and drove it around for about 15 miles. All was good.

For 2 days now when I go to start it, it will not idle cold. After warming up it is fine. But, my problem now is that when at idle with the AC on, the idle drops to 500 and either the AC stops working or the idle will surge fairly rapidly between 500-1000 with the AC turning off and on. I drove about 40 miles around town yesterday. Mostly it was surging but towards the end, I noticed that the idle was smooth at 500 but the AC was blowing warm while at idle. If I turn the AC off the car idles around 750 fairly smoothly. Today, it was cutting off and on again. With the hood open I can see the AC clutch stopping and starting. If I rev the engine just a bit, the AC works fine.

Any ideas?

"reset the computer" How, are you SURE...??

Otherwise my guess you broke the MAF/IAT.

[edbro]

"reset the computer" How, are you SURE...??

I disconnected the battery for 20 minutes. I also pulled the EFI fuse for 5 minutes.

Otherwise my guess you broke the MAF/IAT.

I didn't touch the MAF other that moving the hose it is attached to to get to the IACV. I'm not sure what the IAT is?

[edbro]

Okay, I just took it out for another spin and I got my first CEL. The code was P0120, Throttle Position Sensor. What's that? I assume I don't have something aligned properly?

[Grumpa72]

A/c surging has always been something that I equate with low freon. Have you had yours checked? I don't see how the IACV can possibly affect the a/c.

Gary

[wwest]

"reset the computer" How, are you SURE...??

I disconnected the battery for 20 minutes. I also pulled the EFI fuse for 5 minutes.

Otherwise my guess you broke the MAF/IAT.

I didn't touch the MAF other that moving the hose it is attached to to get to the IACV. I'm not sure what the IAT is?

MAF: Mass AirFlow sensor. IAT: Intake Air Temperature.

And sorry, I miss-spoke I meant to say you broke the IACV.

When the A/C compressor comes on line at idle the IACV is used to raise the mixture volume in order to maintain the idle RPM.

[Mike Bearden]

A/c surging has always been something that I equate with low freon. Have you had yours checked? I don't see how the IACV can possibly affect the a/c.

Gary

We had a droning noise from under the hood...only when the air was on... Lexus had sent out a service letter addressing the droning noise. The dealer replaced one of the AC lines and recharged the system...but their machine was overcharging the system and the surging started...three or four minutes of AC followed by three or four minutes of just air flow. They recalibrated their machine and the the surging problem was solved.

[edbro]

Solved! The black solenoid that sits on the front of the IACV was installed upside down.