I was doing yard cleanup after Irma. I loaded down the truck with a downed tree that I cut up - it was at or just beyond max weight. On the way to the inert dump to drop this mess off it started skipping. I have a blutooth ODBII hooked up and I got the following codes:
P0300 - multiple misfire
P0303 - misfire in cyl #3
P0306 - misfire in cyl #6
P0316 - misfire detected on startup

I cleared the codes while I was waiting in the line and then dumped my load. I got the P0300, P0303, and P0306 on my return trip home. I pulled my #3 and #6 plugs and they look like they are supposed to. I replaced my ignition module about 6 months ago and pulled it and carried it back to where I bought it since it has a lifetime warranty.

I installed the new ignition module and it is still skipping. I am now getting a P0300 and p0306. I swapped the #5 plug wire with the #6 and I am still getting the P0300 and p0306.

The only thing I can think of is maybe a clogged catalytic converter . I will test for that tomorrow.

Any ideas?

 

I tested the catalytic converter using the vacuum method. Start the engine and note the vacuum reading of the intake port at idle. Then increase engine speed to about 2,500 rpm and hold steady. Normal vacuum at idle was 19.1 in/Hg and the acceptable range is 18 to 22 inches Hg. When the engine speed is increased the vacuum pressure drops and it returns to within a couple of inches of the idle reading - it did.

I am using the Torque code reader app. One of its functions is "possible engine codes". The possible codes are P0303 in addition to the codes P0300 and P0306. I started swapping parts.

One of the possible causes is low fuel pressure due to a clogged fuel filter - The canister under the frame rail looks like it has never been changed. It now has a new fuel filter and the codes came back after I had cleared them. No joy.

I next swapped out the spark plugs. I had changed them about 25k miles ago. I cleared the codes and it started without any skips. I ran it down the road - a nice smooth ride and idle. I went back and checked the gap on the old plugs - they were almost twice what they should have been.

 

So sounds good to go now?

When i checked my plugs, one back had no fine wire center electrode left (just the base) but both banks had gaps of around 100 thou, way over the 44 spec'd. No codes though, honestly surprised it ran.

 

What also surprised me was my new Motorcraft plugs were gapped at 65/1000. I had to re-form every one of them.

If I remember correctly the last set were dead on at 44/1000. When I pulled them the closest one was 70/1000 (#4) and the worst was 95/1000 (#6).

 

Yeah, it's a shame but plugs aren't engine specific, so chancing on a set that are factory gapped as you need them is hit and miss.

Curious, which plugs did you get? I bailed on Motorcraft and got NGK's instead.

 

I can get the Motorcraft for about $3 each for the Ranger.

My Fusion with the 1.6L turbo takes a $9 Motorcraft plug and is coming due. I try to stick with OEM as much as possible. It works and with Ford is usually isn't too expensive.

 

Which plug number? There has been some discussion and conflicting reports (inc. from Ford dealers) as to the current plug in the 3.0

 

The 2004 3.0L takes the AGSF32N

There is an optional plug if you have one of the few duel fuel 3.0's that were set up for natural gas.

 

I see, so they're just regular plugs then, not even single platinum by the looks of it.

 

Supposed to be good for 40K miles. The last set only lasted 25K.

 

20-25k is about right for non plat plugs, i see them listed as copper, which is the base plug, hence the very cheap price.

I went for half plats, should last a little longer, don't need the expense of double plats for the 100k life, probably not make back the money.