So I'm tackling the issues of a new car and AC is something I've never had so I'm quite unfamiliar with it.

The car is a '89 CRX Si.
The motor is a Y8 head on a A6 block with a Y8 intake manifold.
The motor is running OBD0 at the moment.

When the car is idling and you turn on the AC, the idle drops and the motor struggles to run. When driving, the car performs flawlessly. There is no issue while driving with the AC running. Just when the car is idling at low RPM and the AC is on, it drops below the normal idling RPM and bogs.

Is there something electrical that turns the idle up via the ECU? I was thinking this was an issue with the non-OBD0 intake manifold and running the engine OBD0.

 

The ecu should bump the idle up to normal when ac is on. At least that happens with mine. What is your car idleing at with ac off and on?

 

What ecu are you running? What is your no load no iacv base idle set at?

 

It is a chipped ECU that I plan on replacing with something I trust more. No load base idle is right at 1000 RPM.

 

that's with the iacv unplugged right?

 

If the IACV is unblocked I beleive idle is set at 600 or 650rpm. Once plugged in it should be to around 800 +/-50rpm.

 

It doesn't throw any codes, I check the IACV plug and wiring.

I'll check with the plug unplugged. I didn't know that was what you were referencing.

 

This is a common issue on the EF's. I've tried in vain numerous times to fix it on my car and other EF's I've messed with. Couldn't ever get it to operate properly. When the engine first bogs down with the compressor engaged, if you rev it up it will then AFTER the rev stay idling higher. But it won't ever on its own bump the idle up.

What I've resorted to is just setting the idle artificially high. I just have my idle set at about 900 at all times so that it doesn't bog down when the compressor engages.

 

James! Such bad news. I will fidget with the IACV and stuff and see if I can edit the ROM and make the AC bump the idle up.

I won't be messing with this again until after I do some engine restoration, so no worries. I'll post some results on what I find.