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Mike S.
Mike S., ASE Certified Technician
Category: Ford
Satisfied Customers: 6793
Experience:  ASE Certified Master Technician
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2004 ford freestar: we changed the plugs and wires and still misfiring

Customer Question

i have a 2004 ford freestar 3.9. The engine all of a sudden starting misfiring. we changed the plugs and wires and still misfiring. The engine light is blinking and the computer readout says cylinder 1 is misfiring. Could it be the coil? We have had a lot of rain here and I wasnt sure if maybe water has gotten into something.
Submitted: 5 years ago.
Category: Ford
Expert:  Mike S. replied 5 years ago.

FlatHead_337 :

I do see a tsb on checking for water in the pcm that may cause a misfire, click here.

JACUSTOMER-vdmhj1b9- :

yes i saw that to

FlatHead_337 :

The ignition coil appears to be all 1 coil. Did you check for spark to #1 spark plug and wire coming from #1 coil?

JACUSTOMER-vdmhj1b9- :

i was told to check spark. if no spark then check the ignition coil. if the resistance is good than the problem si the ignition module under the coil

FlatHead_337 :

Did you do them tests? What were the results?

FlatHead_337 :

Was the code a P0301 or P0300?

JACUSTOMER-vdmhj1b9- :

no not yet. it was late last night when they changed the plugs and wires. was going to start back this morning. i dont know the code number. my husband just said the readout says cylinder 1 is misfiring

FlatHead_337 :

Then it must be P0301, that is for a misfire on #1, a P0300 would be random.

JACUSTOMER-vdmhj1b9- :

so if no spark shoudl they check the ignition coil

FlatHead_337 :

Yes, I am looking up a test procedure, right now.

JACUSTOMER-vdmhj1b9- :

and if the kohms is around 10-20 then i was told the ignition module under the coil is bad

JACUSTOMER-vdmhj1b9- :

but the coil is good

FlatHead_337 :

Who said the coil was good? I believe auto-parts stores have a tester to test modules for free.

JACUSTOMER-vdmhj1b9- :

no one i was told if the kihms is around 10-20 the coil is good but the module is bad

JACUSTOMER-vdmhj1b9- :

kohms

JACUSTOMER-vdmhj1b9- :

if i dont have a spark that is

FlatHead_337 :

I only see a test so far that uses a scope, still looking.

JACUSTOMER-vdmhj1b9- :

i have a test for the coil

JACUSTOMER-vdmhj1b9- :

i am asking what else could be wrong if we are getting spark.

JACUSTOMER-vdmhj1b9- :

changed plugs and wires but still misfiring

JACUSTOMER-vdmhj1b9- :

and what about the module being bad

FlatHead_337 :

You were correct before, if it's not the coil, possibly the module and most auto-parts stores will check the module for free.

JACUSTOMER-vdmhj1b9- :

ok if they are good is it possible then its injectors or valves?

FlatHead_337 :

If you are not getting a spark on 31 then the problem is with the ignition not the fuel, unless of course if you have 2 problems, but no spark means ignition.

JACUSTOMER-vdmhj1b9- :

this happened all of a sudden.no warning. the van ran fine than an hour later i started it and it was misfiring. But it has been raining here for 4 days so i thought maybe some water got in somewhere

JACUSTOMER-vdmhj1b9- :

so if i have no spark then its fuel?

FlatHead_337 :

If you have no spark, the problem is with the ignition which includes the coil, module, spark plugs and wires. Since you already changed the saprk plugs and wires, that leaves the coil or module as the problem. If you do have spark then the problem could be fuel or engine.

JACUSTOMER-vdmhj1b9- :

ok

FlatHead_337 :

Ok, I found it, click here. It's a *.doc so it opens with office or word.

FlatHead_337 :

Here is the wiring diagram, click here. This is a *.pdf which opens with Adobe reader.