"Silent Jackhammer" Sound When AC Running
 

This has been happening for about a month now. When my AC is running, and the compressor kicks in, about 20% of the time I hear what can only be described as a jackhammer noise, but it's not loud. Last week, I had my fuel pump replaced for crickets and the engine ECM reflashed for a bad idle (both were TSB's), but I still have this sound occasionally. Anyone know what this could be?

Here's a video I took while in drive and stopped. You'll hear it twice (ignore the dash rattling) and I manually switched on the AC each time.

[ame="https://www.youtube.com/watch?v=RAq0JvIWuDE"]BRZ Idle 1 - YouTube[/ame]

Really? It's the compressor kicking in and the car raising the RPM's to compensate. Hell, you even took the video of the tach. This is completely normal.

It may be hard to hear in the video, but there's definitely more than just the compressor sound. It's a vibrating metal-on-metal sound, that lasts for about 1 second. It just started doing this about a month ago.

I had to crank the video sound WAY up to hear it, but I do. With your extensive list of mods, it could be a lot of things. I'd start with checking to see if the exhaust is making contact with something.

open loop and close loop

Could you elaborate on this? Not familiar.

if the car ECU is in close loop the AC is on and if it in open loop the AC off that save same torque

Got it, but is there a reason it would cause this sound when going to closed loop?

I watched the video again using car sound system eith bass . I think that clicks is normal . Coz the AC system turn off the compressor if the AC air cooler is cools then it should be . To keep it dry from ice

I caught it again this morning, and you can hear the "jackhammer" much clearer in this video (between 4-5 seconds). It seems to happen when the car is cold, then dissipates over time. I never hear it while moving. I do have quite a few mods, but nothing near the engine that would make this sound.

[ame="https://www.youtube.com/watch?v=TxWa9WlBWME"]BRZ AC Sounds - YouTube[/ame]

False,

Open loop is when the computer does NO fuel adjustment and runs on programmed parameters, usually when the car is cold, Closed loop is when the computer puts the car into fuel control, usually after the car is warmed up.

AC on / off does not make the car change open / closed loop.

This usually happens when the compressor has too much oil or pressure when turning the compressor on, kind of like a hydrolock but the clutch compensates by making that nose, similar to slippage.

If it happens a lot you should have it looked at by the dealer and tell them it need to sit over night for the condition to happen. I have seen this happen on a lot of Tacoma's and we had to replace the compressor and check the oil level.

Test your frs

If you had a clutch instead of paddle shifters you would not have the noise.