Will bad oxygen sensor or idle air control valve cause hard start? - Mustang Evolution

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Old 04-02-2010, 04:30 AM   #1
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Will bad oxygen sensor or idle air control valve cause hard start?

i own a 2002 ford mustang gt, automatic. My car has a hard time starting after driving it for awhile (it cranks, but dies off right after attempting to start while making a bop'ing noise). i had my fuel related issue taken care of (fuel pump, fuel filter, fuel pressure regulator, etc..) electrical-wise, battery, starter, alternator are all fine. my theory are the above mentioned parts, any ideas guys? (this only occur after the vehicle have been driven around for awhile). thanks for reading.
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Old 04-02-2010, 05:02 AM   #2
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Will bad oxygen sensor or idle air control valve cause hard start?

I suppose they could cause for a hard start, but if either of those things is defective they will cause a malfunction indicator light which means you can have a diagnostic scan performed to determine exactly what the problem is before throwing away hundreds of dollars replacing good parts.
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Old 04-02-2010, 05:30 AM   #3
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Will bad oxygen sensor or idle air control valve cause hard start?

Hard starting based on temperature is almost always somehow related to the air fuel ratio not being correct for the current conditions. On older carbureted cars when the choke would stick closed they would be hard to start when hot and start easy when cold.

On modern electronically fuel injected vehicles the causes multiply exponentially. In your case you would need to check your coolant temperature sensor, intake air temperature sensor, and check for fuel pressure leak down caused by a hung fuel injector. I suspect that you will find one of these to be the cause of your incorrect air fuel ratio problem.
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Old 04-02-2010, 05:40 AM   #4
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Will bad oxygen sensor or idle air control valve cause hard start?

The PCM does not monitor the O2 sensor during cranking.
The IAC might possibly cause a hard start, but I suspect that the symptom would be far more likely an idle problem after it starts.

Put a fuel guage on it and check to see if the pressure is bleeding down when you turn the engine off. This could indicate a leaky injector that might not exhibit any other symptom after start up.
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Old 04-02-2010, 06:01 AM   #5
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Will bad oxygen sensor or idle air control valve cause hard start?

if it was the 02 sensor then it should throw a code. besides that it would make the plugs black. i suppose it could cause it hard to start but like the 02 sensor if the idle air control sensor was bad then it would throw a code too. you might take the idle air control off and clean it.
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Old 04-02-2010, 06:33 AM   #6
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Will bad oxygen sensor or idle air control valve cause hard start?

Hello bx5
this a tough one and you are going to get many opinions on this and they will be diff. i read your question 4 times. My thoughts it must be the distributor or timing issue. My 2nd thought is fuel injectors but i have problems with that. Good Luck BS
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Old 04-02-2010, 07:24 AM   #7
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Will bad oxygen sensor or idle air control valve cause hard start?

Yes it could.
But it could also be a faulty temp sensor.
But my bet is on it needing a complete tune up!
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