Car wants to die with A/C on and idle surge.

[94RedGt]

Hey guys my 94 Mustang GT has been driving me crazy ever since i got it, when ever i turn the a/c on it seems to run fine but the idle gets a bit weird and it will start to surge a bit then wants to die if i dont step on the gas, very annoying while waiting for red lights on hills, for whatever reason it runs fine while the car is moving but when i stop at a red light the idle will hang around 900-1000 rpm then it will start going down slowly to were its suppost to be then it will sometimes surge then dies if i dont manually open the throttle.

It will die faster if while standing still with the a/c on and i move the steering wheel, its like if the engine suddently had too much load on it and quits, i have already corrected my TPS voltage, even got a new idle sensor and made the ecm relearn the idle by manually setting the idle with the IAC valva was disconnected. I took it to my friends shop were he hooked up a scanner wich tells u at how much temp and volt everything is running and the only thing he found was that one of the O2 sensors was not working properly, and he also told me that Bank #1 wich is the right side of the engine was running leaner than the left bank. I will be buying two new O2 sensors and see if this fixes the idle problems, i mean brand new idle speed control valve and tps volt set correctly, timing set at 10 and i still get this dang idle surge, what is also funny is that the engine idles way smoother with the IAC disconnected, ofc it dies if i put a load on the motor since the computer cant correct it to compensate.

Can the A/c low preassure switch be bad ? I have noticed that my A/C comp reraly does a cycle , can too much preassure be building up in the ac system making the idle bad when the car is not moving ?

 

[rz5.0]

Reset your base idle. Check for vac leaks grounds. And alt supplying enough current

 

[94RedGt]

The idle has been set and all vacuum leaks and hoses problems have been eliminated, the alternator is new and the gauge says is charging , also confirmed with a volt meter and with everything on its charging 13.60 or around that. Should it be higher ?

 

[CC'S95GT]

Alt should be closer to 14.5vdc. What is your idle rpm set to?
Is your speedo working?
On a recent trip my speedo wasn't working and I noticed occasionally when I roll to a stop with the a/c on, the car would stall. I've never had this prob before. So I can only assume that the computer wasn't recieving a signal from the trans therefore the computer had no way of knowing when the idle needed to be bumped up when stoped or slowing down. I would have thought the signal from the tach would be used but maybe the speedo is used too.

 

[mustangspartan]

Sounds more like the ac unit is going bad either the clutch or the unit itself. If its turning on and off a lot and I would check before you spend moremoney into it how much fluid is in the ac iteself. If its low top it off.

 

[extreme_21]

The idle has been set and all vacuum leaks and hoses problems have been eliminated, the alternator is new and the gauge says is charging , also confirmed with a volt meter and with everything on its charging 13.60 or around that. Should it be higher ?

How did you check the vacuum to verify there is no leaks, did you use a vacuum pump and/or a smoke test and pressure it with nitrogen?? What were the reading from the vacuum pump/gauge?? If your running lean, idle is surging and averages at 900-1000rpm...There is a high chance you have a vacuum leak and haven't found it yet. There are various vacuum circuits, which circuit did you test??