Engine almost stalls with Heater / AC on....

[mydland89]

My 99 explorer is running and when I have either the heat or the A/C on while running, the clutch on a pump ( I'm guessing) engages and it draws the engine down for about 1-2 seconds...and then it goes back to idle....it does it over and over again...when the heater / Air Conditioning is off, it doesnt happen....I noticed that I am low on power steering fluid and my trans fluid was also low...what gives???? I just applied for a $1000 loan to get new shocks, plugs and wires, new tranny cooler, U-joints, etc etc...I have just crossed the 90,000 barrier and want to get everything done before winter sets in and freezes the northeast for 6 months again....thanks in advance...

 

[TPLYNCH]

The idle dip is your A/C compressor engaging. The IAC's job is to compensate for that draw. If your IAC is clogged or malfunctioning, it will allow the engine to almost stall or stall. Try cleaning the IAC. There is a post on the next page of threads with instructions/pictures on how to clean/replace I think. At 90K, you will probably be low on several fluids, especially if you've never topped them off (PS) or flushed/changed filter (Tranny).

 

[glfredrick]

You also might want to do a visual inspection of the air conditioner pump - turn on the air, and then watch under the hood - how often does the unit cycle? If it comes on and off fairly quicly then you are also likely low on freon. It should come on and stay on for at least a while before it cycles.

 

[Glacier991]

How long the A/C "ON" cycle time is will depend on many factors. In cold weather, it will cycle rather fast (any annoyingly so), but glfrederick is right, in summertime temps, the cycling should not be that rapid (but it WILL cycle nevertheless). Ford even has a chart of acceptable cycle times based on various factors.