Stalling with heat or AC

I have a 2002 Taurus that is intermitantly stalling. It goes for days, weeks, or months without doing it, then all the sudden it happens 3 or 4 times a day. It can happen when setting still or when driving at 60 mph. I have watched to see what is common about the times it happens, and it seems that it happens always when we have the AC or heater/defrost on. Could there be anything there that would cause this?

If it does it when you have the AC on, it could be your AC compressor is shot. When it does this will your car turn over, if so does it turn over hard? If it's your compressor it would lock that pulley solid causing the belt to turn hard (you'd probably hear squealing and smell burnt rubber too).

Denis

The car seems to turn over fine. When the stalling happens, we do here a quick squeak, however, what would be causing it when the heat/defrost is on?

vacuum leak?

How easy is a vacuum leak to diagnose and fix?

The car seems to turn over fine. When the stalling happens, we do here a quick squeak, however, what would be causing it when the heat/defrost is on?

When you select "defrost," the A/C compressor engages as long as the outside temperature is above freezing. The purpose here is the A/C compressor takes the humidity out of the air, allowing the windows to defrost more quickly. So, if your compressor is seized as another poster mentioned, it could explain the quick chirp (belt slipping when the compressor clutch engages) followed by the engine dying due to the load of the compressor.

-Rod

Ah ok...Im starting to understand it all now. My final question is, if this were the case, would the AC and defrost/heat work? It will work without fail for a while, then the problems show up...then go without problems again.

Ah ok...Im starting to understand it all now. My final question is, if this were the case, would the AC and defrost/heat work? It will work without fail for a while, then the problems show up...then go without problems again.

Well, probably not. The A/C, when it works, gets cold? The blower motor will still work, so air will still blow, but if the compressor is seized, it won't create COLD air. I would not expect a seized compressor to work sometimes. But, I haven't seen everything in my short life.

-Rod

Rod, yes the AC gets cold and the heat gets hot.

Does the engine do anything else just before it stalls??? Or is it like you've turned off the key??

My '03 had a problem where just like yours, it'd be fine for weeks/months.... then just start it 3 or 4 times then stop again. It was also AC related, but my problem with stalling only occured at idle in or out of gear... never while driving.

Does the engine feel like its running rough before it dies, sputtering, or any fluttering in the RPM's before it dies??

It's very odd what it does. It does it both in and out of gear. When Im driving, the dash lights all come on, the head lights dim, and the car stalls. If I press the gas, it will kick back in and away it goes. It will jerk a little before it stalls and you can hear a quick chirp....all which are probably normal when you stall at speed.

When Im stopped or even in park, the speedometer races up then down, up then down, dash lights come on, then stalls.

when the a/c kicks on the ecm raises the engine rpm by ~100-200 rpm so the engine doesnt stall out with the extra load of the compressor. this is only noticable at idle speed. run your engine at idle w/o the a/c on (when engine is warm). record the rpm. turn the a/c on and you should instantly see the rpm raise. if it doesnt then you have a idle control motor malfunction. hope this helps.

I have a very similar problem with my 98, except I hadn't noticed a corrolation between the a/c and it dying. just for reference my idle control motor was replaced and it didn't fix it, as well as a fuel cleaning and trannie work. it does it during summer months only(in florida) during a florida winter it was fine. it just started up again

Go with Busa4.... When I had my problem, once the RPM's dropped below a point, all my dash lights would also come on, and hitting the gas stopped the problem (at least until I let off the gas...lol)

Turned out that for some reason, the Base idle speed was incorrect in the computer (it was idleing too low w/o the AC on), and when I turned the AC on, the computer would start to Freak out and out go too far each way to correct for the extra load. There were no actual bad parts, just had to have the Computer reprogrammed, and it's been fine since.

All of your symptoms fit, except for it stalling "at speed"... then you already have your foot on the gas to maintain 60mph, so any kind of IDLE problem is not relevant at that time. Because of that, I'd think you have a electrical problem somewhere.... maybe a open/short in a wire somewhere, bad relay.... something. Unless its the computer itself like Mine.... I would notice "surging" while driving before it was reprogrammed.

Either way, I'd take it in with the new info about the AC.... after you check the RPM's like Busa4 said, then have them check things with that info.

Good Luck... Electrical problems are a major PIA

Thanks everyone for the help. Ive had it in 2 different times and the mechanics havent found any problems. I guess the next thing is to look for electrical problems.

One more thought: Monitor the battery voltage while the car is running, then turn the A/C on and see what happens. The best tool for this would be a digital oscilloscope that you can set the trigger level on. Set the trigger level to 10 Vdc or so, arm the scope, and turn the A/C on. My thought here is if you have a bad alternator and/or a weak battery, the extra load from the A/C compressor clutch, cooling fan, and blower motor could be causing an instantaneous current draw that causes the battery to drop below the threshold for the ECU to operate (probably around 9.5 volts DC). So, you turn the A/C on, the cooling fan kicks in as does the A/C compressor, the battery voltage drops to 9 Vdc, and the ECU "shuts off" due to insufficient voltage, which in turn causes the engine to die. A high sample rate oscilloscope can catch even the quickest drop in battery voltage to let you see what is going on with the electrical system.

-Rod

Thanks everyone for the help. Ive had it in 2 different times and the mechanics havent found any problems. I guess the next thing is to look for electrical problems.