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Virtual Wrench
Virtual Wrench, Ford Mechanic
Category: Ford
Satisfied Customers: 14620
Experience:  35 years Master Mechanic
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my 2003 ford focus zxw shuts off after coming to a stop at

Resolved Question:

my 2003 ford focus zxw shuts off after coming to a stop at a stoplight or stop sign (e.g. bottom of an exit ramp) following an hour or more of sustained highway driving. When I push the gas to go again, the car stalls out and shuts down completely, like I took my foot off an invisible clutch pedal too quickly. Can't replicate it with city driving, it only happens after driving at highway speeds (55-75mph) for a sustained period of time. Local mechanics can't figure it out, since they don't have the time to drive around for a few hours. No check engine light or other warning indicators come on, so no codes on the computer. What could be wrong?
Submitted: 5 years ago.
Category: Ford
Expert:  Virtual Wrench replied 5 years ago.
Welcome,

It has been my experience that this can be caused from a faulty Idle Air Control valve. It needs to be removed and cleaned throughly then reinstalled. Most of the time is takes care of it but may just need to be replaced. It doesnt set a code and fits the description you gave.

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Expert:  Virtual Wrench replied 5 years ago.
Welcome,

It has been my experience that this can be caused from a faulty Idle Air Control valve. It needs to be removed and cleaned throughly then reinstalled. Most of the time is takes care of it but may just need to be replaced. It doesnt set a code and fits the description you gave.

graphic
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If you have any further questions or need more help at all please feel free to reply. If not, Please remember we use an honor system and you must click on accept for me to receive credit for assisting you.
Customer: replied 5 years ago.
Would a faulty IAC also cause my car to stall each time I came to a stop, regardless of the number of hours/speed I was driving? The problem only occurs after hours of sustained driving at highway speeds, not in the city. Our local mechanic suggested we reprogram the computer. This did nothing. The last time this happened, I managed to restart the engine, but when I flipped on the 1) headlights, the engine stalled; restart, then 2) defrost (AC engaged), stalled. Then restart. After that, we drove for a while down the highway, and it cut in and out (as if it were about to stall) while at speed on the highway. Once home and at rest for the overnight, it hasn't done it since. But, we also haven't been on another highway trip since.

Does this still sound like an IAC problem? I've read elsewhere that it could be something fuel-management related?
Expert:  Virtual Wrench replied 5 years ago.
Hi,

The engine speed is reduced when you turn those accessories on like the defrost (ac engages) and the alternator drags it down some when the lights are turned on so that is hard to say if its causing this but i dont think so. I would still be very suspicious of the air control valve...it could be fuel management related, but it could be a lot of things but i dont like just listing every single possibility only the most common if i cant test it myself.
Customer: replied 5 years ago.
Ok, thanks for this. 1 last question: Is this something that a reasonably competent but not mechanically inclined owner could do, or should I have a mechanic do it? If I should have a mechanic do it, what do I ask for?
Expert:  Virtual Wrench replied 5 years ago.
Hi,

It would be best to let your mechanic take a look at it and remove it and de-carbon the valve and the passage/port that it connects to. Just tell them that you suspect a fault in the IAC (idle air control) and they should know exactly what you mean. If they dont know what IAC valve means right away,,,,dont let them even work on it :-)

Best wishes my friend!

LJ


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