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Old 07-03-2012, 17:45   #1 (permalink)
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07 F-150 rough idle

My 07 F-150 5.4 has a rough idle during a cold start for about 1 minute. It happens mostly when the weather is chilly or cold. Also after the first start it doesn't do it the rest of the day. Of coarse they can't find anything wrong and tell me there are no updates for anything like that.
Has anyone heard of anything like this?
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Old 07-03-2012, 18:35   #2 (permalink)
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Re: 07 F-150 rough idle

Check your vacuum lines, mine was doing the same thing, only mine has a 91 5.0. Replaced vacuum line to EGR and MAP, smoothed her right out.
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Old 07-03-2012, 19:02   #3 (permalink)
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Re: 07 F-150 rough idle

Autozone will pull codes for free. That will tell you if anything else is wrong.
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Old 07-04-2012, 14:31   #4 (permalink)
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Re: 07 F-150 rough idle

I've got a Scan Gauge II which will show the codes and it has never had one. It's odd because it'll be fine the rest of the day. In warm weather it never does it either. I've had 2 Expeditions with the 5.4 and I don't remember it in them.

BTW thanks for the thoughts.
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Old 07-06-2012, 21:45   #5 (permalink)
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Re: 07 F-150 rough idle

There is a problem but those who are looking at it are not investigating deep enough.
This may be a bit deep but when you turn the ignition switch to Run, the PCM looks at the values of the main tempersture sensors to determine it is to be a cold start by their values.
This sets the idle air opening, a richer amount of fuel and sets ignition timing.
If this sequence has a failure or out of spec sensor or action, the idle will have an issue especially in cold temps.
To go on, the reason is smooths out is when the OX sensors take over fuel control and the coolant temp begins to rise then the motor runs smooth as it should.
Certainly after the motor gets warm the cold start sequence values are "not the same" but is still looked at the same way upon ignition switch RUN position where it sees the sensors at a warmer resistance so the conditions 'set' for start are not the same.
What a good tech needs to do is take his scanner and look at the sensors under cold start conditions and compare with factory info.
If you cannot find a shop that can and will do it then it's a sad day for you and shop compentency.
You came here to ask, now you have some idea what's supposed to go on and how it can be looked at.
Good luck.
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Old 07-06-2012, 21:48   #6 (permalink)
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Re: 07 F-150 rough idle

There is a problem but those who are looking at it are not investigating deep enough.
This may be a bit deep but when you turn the ignition switch to Run, the PCM (computer) looks at the values of the main tempersture sensors to determine it is to be a cold start by their values.
This sets the idle air opening, a richer amount of fuel and sets ignition timing.
If this sequence has a failure or out of spec sensor or action, the idle will have an issue especially in cold temps.
To go on, the reason is smooths out is when the OX sensors take over fuel control and the coolant temp begins to rise then the motor runs smooth as it should.
Certainly after the motor gets warm the cold start sequence values are "not the same" but is still looked at the same way upon ignition switch RUN position where it sees the sensors at a warmer resistance so the conditions 'set' for warm/hot starts are not the same.
What a good tech needs to do is take his scanner and look at the sensors under cold start conditions and compare with factory info.
If you cannot find a shop that can and will do it then it's a sad day for you and shop compentency.
You came here to ask because you got no satisfaction, now you have some idea what's supposed to go on and how it can be looked at.
Good luck.
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