2003 check engine light beow 60 degrees - Ranger-Forums - The Ultimate Ford Ranger Resource


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Old 02-12-2015
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2003 check engine light beow 60 degrees

I have a 2003 3.o flex fuel during winter months when tempature is below 60 degrees it idles rough and the check engine light comes on as soon as the weather warms up the check engine light goes off after 60 miles whats causesing this does not happen in summer months
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Old 02-12-2015
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Get the codes in memory to see why computer notified you with CEL(check engine light).
Anytime the CEL comes on the computer saves a code number for why it came on.
Code numbers NEVER ID the problem, ever.
The code number tells you what sensor FOUND the problem, so don't "shoot the messenger", i.e. don't get a new sensor.

Most Auto Parts stores read the codes for free, write them down.

Assuming outside temp is 40degF:
Does it idle rough but drive OK at higher RPMs?

Does it only idle rough when engine is cold but not after engine warms up?
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Old 02-13-2015
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seems to run fine at higher rpm idles rough when engine warms up
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Old 02-13-2015
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codes reoprt missfire #6
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Usually with a Misfire the CEL will Flash during the misfire.

And the CEL going off after that long of a time(assuming 1 hour) would not be from misfire code.

3.0l Ranger engines around your year did have a few issues with misfires.
One was a bad run of Coils I will see if I can find those serial numbers, there was a TSB for that, but it was a Pinging issue when accelerating, along with misfires.

The other was bad exhaust valve seats, expensive repair, new heads were needed.

Colder weather means colder air, cold air is denser, has more oxygen in it.
The air/fuel mix for a gasoline engine is 14:1, oxygen to fuel
And this is a weight ratio NOT volume, which is why fuel "pre-vaporizers" are a scam, just FYI.

Warm air rises above cold air because..................it is lighter, has less oxygen.
So in colder weather the computer needs to add more fuel to get the same 14:1 ratio
This is why MPG goes down in the winter and why the engine feels like it has more power in the winter, it needs to burn more fuel with the colder air.

Say it is 75degF outside and a cylinder pulls in 10cubic inches of air on it's intake stroke(this is a volume) and that air has 28 units of oxygen(weight), the computer would add 2 units of fuel(weight) to get the 14:1 ratio
At 40degF outside temp, the cylinder still pulls in the same 10cubic inches of air, but this colder air has 35 units of oxygen, computer has to add 2.5 units of fuel to get the same 14:1 ratio
And the computer has an IAT(intake air temp) sensor just for this reason, but the MAF sensor also does this because it is a heated wire sensor, the wire cools more in colder/denser air, so computer can compensate for denser air.
Above is an example not meant to be exact numbers.

When a fuel mix is rich it is harder to ignite, so a weaker spark may work fine in warm air mix but not be able to ignite cold air mix, just guessing.
This could be because of the coil, or spark plug and wire for #6
Or could be start of a recessed exhaust valve seat in #6, this lowers compression which makes igniting air/fuel mix harder, more so with colder air rich mix

Last edited by RonD; 02-13-2015 at 11:25 AM.
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