Year: 2010

Make: Ford

Model: Focus SES

Transmission: 5 Speed Manual

Engine: 2.0L I-4

Mileage: 79K

Last summer my Focus stalled while climbing a hill with the AC on. It was a hot day and I had the AC cranked on high. I immediately put the clutch in and tried starting the engine again before I started rolling backwards down the hill but it just would not start. I then maneuvered to the side of the road and kept trying to start the engine. The engine would hesitate and sputter, nearly starting, but then die as soon as I tried to give it a little gas to keep the RPMs up. I had it towed to a nearby Ford dealer and it finally started again in the dealership parking lot after sitting for an hour. The mechanics there claimed in was a faulty fuel pump, and wanted to charge me $800 to import a replacement part (not including labor)! I told them that I'd get a second opinion and then drove it home with the AC off. I have been daily driving it with no AC for 9 months now and it has not stalled once and I think my fuel pump is working just fine. However, today I tried using the AC again and after 30-40 minutes the engine did stall.

Poor graduate student here looking to save some money. Any insight is appreciated!

  • 1
    So, this hill : slight rise in the road or Mount Washington?
    – Solar Mike
    Commented May 10, 2019 at 4:48
  • It's about a 7% grade hill. Commented May 10, 2019 at 4:51
  • What’s with the downvote? Commented May 10, 2019 at 22:04
  • Why ask me about the downvote? I will vote if you wish, but have not yet....
    – Solar Mike
    Commented May 11, 2019 at 5:23
  • 1
    Using paragraphs to avoid a wall of text is always a good idea...
    – Solar Mike
    Commented May 11, 2019 at 5:31

1 Answer 1


I'm too new to comment, and you technically don't ask a question but I assume you want to know why your car stalls after the AC has been on for a while. Running the AC takes a bit of power so its normal to see the RPMs move on a car when you kick it on. Besides your issue being caused by the AC compressor or it's clutch its is possible your vehicle isn't producing enough HP to run the AC while the car is idling. I saw the same issue with an 07 mustang, the car would drive fine with the AC on with the RPMs up, but once you hit the clutch it would begin to stall. It's throttle body assembly was gunked up, so the car wasn't producing enough strength in idle. But the car drove fine because when you pushed on the gas it over compensated for the strength it needed.

I can't tell you exactly whats wrong with your car because I don't have enough info, but my answer is to roll down your windows to stay cool. And put money aside, if it is a fuel delivery issue it will eventually fail and the car probably won't run. If its the AC pump/clutch leave it off an put the windows down.

  • 2
    I second the throttle body suggestion. The OP might try cleaning the throttle body and idle air control valve (if present), and the mass air flow/manifold absolute pressure sensor also. If they're dirty, any additional load can and will make the engine stall. The OP can also try giving a good cleaning to the condenser fins in order to reduce the AC compressor head pressure and therefore the engine load.
    – Al_
    Commented May 14, 2019 at 9:56

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