348 Engine Cuts off when the AC is on.

what done to car since car ran and a/c ran well too? any services? Fixed anything else?

 

Some thing easy to check is air bypass screws and throttle balance.

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Does the engine cut out with the engine at higher rpms or just, say, at idle?

 

Thanks. During your run, could you let us know if your engine idle goes up when you turn on your AC?

 

Should not affect idle speed much, ECU does that for the most part, sometimes when ac kicks on the load pulls down the motor and it stalls, sometimes when slowing down it stalls. Those bypass parts tend to get gummed up. See if resolves it over time. Probably want to do ECU reset btw.

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Interesting. The AC system is supposed to tell the Motronic ECUs that the AC compressor has been turned on (and compensate for the increased load). On my F355, the idle speed goes up.

This presents a few possibilities:
The 12 volt signal from the HVAC system is not reaching the Motronic ECUs.
The A/C system is putting an unusual load on the engine (new compressor faulty, pressures too high?) and even the higher idle command is not compensating for the load.
An idle control issue?

(Edit: sorry, crossposted with Eric. I didn't think the rpms would go down)

 

They dip then go back up, but if the engine is not getting enough air with throttle ates closed it can stall. Usually gummed up bypass screws, the correct action is to remove and clean them and the port itself but backing them out is a quick way to see if that's the issue. Could be something else but that seems to fix ac related stalls for most.

When I removed my air screws they were coated with grime noticably thick, had to use 400 grit to clean them off.

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Typically it should be the other way around, usually its an idle-up when AC is on to account for the load of the compressor.
It does sound like there is a bypass issue there, but until you figure it out increasing the idle by the air bleed will work, idle should be about 950 +/- 50 so its a bit high but at least you wont stall!!

 

Unplug battery for 30 min, start car AC off, let it idle and don't touch anything not ac not gas pedal nothing for 15 minutes.

Reset is not super needed in this case, it will adjust. If your car starts fine and idles fine don't bother resetting ecu it will have to re-gather lots of information it gathered over time.