98 Windstar MIL code p300 misfire

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goobers04@gmail.com - 17 Dec 2006 05:09 GMT

Hi there,

I'm looking to solve my problem for not alot of money (aren't we all),
I have done alot of research but I do need some insight.

My van started running poorly, but only when it rained. We replaced the
spark plug wires as they were original. Next rain storm the same thing
happened. The van sputtered on idle, backfired on acceleration but
above idle was fine.

Eventually it threw a code, P0340 which is camshaft position sensor
circuit. We replaced the sensor, code was cleared.

Next rain storm, same thing happened, except the MIL started flashing
while it sputtered on idle and backfired on acceleration. Once it
stopped raining and things dried out, the van ran like a top. The new
code was P0300, Random misfire.

The common causes seem to be, spark plug wires, CMP, spark plugs, EGR,
coil pack etc. The problem is this problem ONLY occurs in the rain,
never any other time until today. It rained alot yesterday and the van
was still running poorly today and has started backfiring on
acceleration even at 100 km/h. My mechanic is leaning towards coil pack
now, which makes sense to me.

Anyone ever had this problem only in the rain?

Information:
98 Windstar GL 3.8L
162,000 km's
Replaced:
Spark plug wires
Camshaft position sensor

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marks542004@yahoo.com - 17 Dec 2006 07:42 GMT

> Hi there,
>
[quoted text clipped - 29 lines]
> Spark plug wires
> Camshaft position sensor

Not much help to you but I had this problem on one of my first cars. It
turned out to be a faulty (cracked) distributor cap and bad cover on
the coil lead. When water spray collected enough mist on the
distributor or coil it started shorting . Let everything dry out and no
further problem.

Unless you can find an electrical connection exposed to the water that
might be shorting to ground and seal it up I dunno.

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Don - 17 Dec 2006 15:12 GMT

>Hi there,
>
[quoted text clipped - 29 lines]
>Spark plug wires
>Camshaft position sensor

If the van dries out and starts to run better get a plant sprayer
bottle full of water and spray the coil pack and see if that provokes
a missfire. Your "mechanic" should have known to do this the moment
you mentioned the problem correlates with rain.

Don
www.donsautomotive.com

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Comboverfish - 17 Dec 2006 18:15 GMT

> Hi there,
>
[quoted text clipped - 29 lines]
> Spark plug wires
> Camshaft position sensor

To add to the good responses so far, you may just have junk replacement
wires. I wouldn't trust anything other than OEM or high quality
replacements on a demanding ignition system like yours. Your mechanic
is probably right about the coil, but I wouldn't rule out the wires
just because they are new.

OBDII Fords are reluctant to set specific cylinder misfire codes and
often only set a P0300 if the misfire duration on any specific cylinder
is too intermittant. You could actually have one cylinder misfiring
due to a wire, or two cylinders due to a companion coil inside the
coilpack assembly. Water and an ignition scope could help in this
diagnosis, or simply water and visual/audial inspection for spark
arcing to ground anywhere around the coil or wires.

Given that even a Motorcraft brand coil pack is <$100 it wouldn't be
the end of the world to replace it on a hunch. They're definitely not
bulletproof.

Toyota MDT in MO

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