Hi there...First post for me, though I am a long-time Ford owner and fan of this forum. I have found some posts detailing problems similar to what I am experiencing with my van, but with a significant difference - my miss is severe and decidedly intermittent. I will be as detailed as I can.


After about an hour of driving following driving on a washboard dirt road for about 15 miles, at slow speed but with significant vibration, my van developed a noticeable miss. I put injector cleaner in the gas, which didn't help at all. The "service engine soon" light came on. When I put the obd reader on it, I pulled codes P0301 and P0351. Took it to a shop, they spent two days trying to fix it: replaced #1 injector, #1 COP, the wiring lead to the #1 COP, looked for vacuum leaks, etc. No affect at all. They suggested I take it to a shop they recommended, that specializes in analyzing, fixing, or replacing the pcm. At this point the miss had been there for about 3 weeks, though I hadn't been driving it much in this time.


I took it home, and two days later, with no other work on it, it suddenly ran fine. The trouble codes (I cleared them) stayed gone. Because the problem was gone, I never pursued taking it to the pcm shop. I did call the other shop back, and the owner proposed that maybe the pcm had needed to "learn" the engine again...


Anyway, it has now done this cycle two more times. It ran fine for about a month, then started the miss again, same codes. It had the miss for a couple weeks, then ran fine again for over a month. About 2 weeks ago, after a rainy day (if that matters - rain wasn't involved in the other incidents), it started missing again. Each time the codes are 301 and 351.


I used noid lights to check the injector electrical pulses on the #1 cylinder, and it seemed fine.


I read in one of the posts today about resetting the fuel cut off switch (the impact safety fuel cut off), so I haven't done that yet but will later today.


I could sure use some suggestions. I really don't want to take it to that brain surgeon unless its a pretty sure bet that is the problem. It seems logical that it is, with an intermittent problem like this, but I would rather exhaust all other possibilities first.


Thanks ahead of time...

 

Maybe, check the ground wires. Computers are finicky that way.

 

the PCM will re-learn its strategies within the first 10 miles you drive---it will typically NOT induce the misfires you're having.

As Vettex says you could have something as simple as loose grounds from the PCM to the chassis ground---those will be found inside a wiring harness---this is where the EVTM's come in uber-handy.

The shop replacing the #1 cylinder components did pretty much the right thing but without fully diagnosing the PCM while in operation there's not a lot left to change, parts wise.

I would offer because your codes are recurring its an electrical problem, perhaps due the PCM OR one of the wires or connecting pins inside a wiring harness connector from the PCM all the way to the connectors closest to #1. Again the EVTM would be most helpful here.

Go to AutoZone for their free schematics---view or print one or more that show your pathway from the PCM to #1. I have a printed EVTM which isn't helpful to you----sorry.