I have a 1998 F150 4.6l 4x4. While driving, a misfire condition developed. I was able to get the truck home and park it where it sat several days until I could get to it in better weather.

The truck would not restart when I got to it. I checked the OBD codes with a bluetooth scan device and only pulled up a P0307 (#7 misfire detected). A second scanner also only detected the P0307.
I tested the plug wire for continuity with a meter and it tests OK.
Since the wires and plugs only have 10-15k on them anyway (this truck is rarely driven at its age), I plopped on a new coil pack.
Still crank but no action; but, the battery had run down a bit, so I charged it up, and tried again.

It caught briefly after cranking about 2 seconds, ran perfectly for about 1 second, then died immediately. It felt like a normal start until it died.

Suspecting a fuel issue, I sprayed some ether into the intake to see if the engine would fire. It did not.

At this point, I'm thinking there is some abnormal electrical problem, or something is deliberately preventing restart?

I'm looking for direction/guidance. What to do next? Has anyone ever had this happen?

Any help is appreciated!

Thanks

sirrobocop

 

Did the check engine light come on at all? And if it did was it flashing? One cylinder misfiring surely isn't enough to prevent it from running. Being an older truck that spends a lot of time sitting around there is a chance it's developed one heck of a vacuum leak somewhere. When I had a similar issue as you (would start and run great then shut off immediately as if i'd removed the key) it ended up being an ignition control module causing the issues. Being that I can't see the truck though i'm not going to recommend running out and ordering a bunch of parts. You can take it to be checked at the parts store though I believe. Is the Battery good? Maybe the alternator is failing and not charging it properly?

 

RE: LIGHT - The check engine light came on; then as the miss increased, I got FLASH from the engine lite. It chugged up the hill to the drive way and had enough power to park in a "rough terrain" section of the yard where I park the current project. It would not start a couple days later, so I began trouble shooting. I tried the coil, because a similar issue a year ago affected the other bank, and I don't recall if I changed both or just one.

RE: Charge - The truck might sit a couple months at a time; I keep a trickle charger on it that runs for an hour a day to keep the battery up. My son borrowed my charger a month ago and didn't bring it back until I called him yesterday. Troubleshooting multiple times brought the battery down pretty quick. I charged it just to eliminate that as an issue, because it usually needs a couple seconds to catch and fire up. Odd that it did fire briefly after charging.

When it went down, I had been driving it for a day or so for yardwork, then the issue started.

I recently filled the gas tank, but since the Ether doesn't get a response, I think that filled tank is just a coincidence rather than possible water in the gas, and that the problem is therefore electrical.

I pulled the #7 plug today; lightly bronzed, perfect condition, correct gap. I swapped out the plug wire in case it was shorting to the block thru the boot. No change in condition, so we've now swapped coil pack, wire, and checked for a wet / corroded plug, and see no issue.

I am thinking I need to check with an induction light to see if spark is gone on all cylinders; this makes sense to me, given the no start condition. This might point at something else, then.

 

A flashing CEL indicates a multiple misfire condition has occurred and therefore would likely be more than just cylinder #7. I would check things out related to that bank directly like a cam position sensor or crank position sensor (could effect both banks). Possible ignition control module rather than just one coil. Let us know what happens when you check each cylinder for spark. If you're missing spark on multiple cylinders then you can at least rule out some stuff.

 

Thanks Shift lock, here's what we have...

I had to wait to get a new light to test the wires.

Today when we tested the wires, the truck again started very briefly and died.
Testing a few wires at random indicated a few of them had some spark...butttttttt....I got a note pad to mark which ones were and were not firing, and tested them one at a time at the plug and coil - and there was no spark at all. So, we had some spark for about 10 seconds on a couple of tried starts, and nothing after that.

Bad computer? Gets hot and won't roll anything to either coil pack?

Anyone? A bit out on a limb here


Next step?

Thanks

sirrobocop

 

Additional Information:

I swapped the EEC and the Horn relay in the box under the hood with no effect (tested the horn to verify relay).
I ran a continuity light over all the fuses in the engine area, and all are intact.

Still cranks fine but no start.

What next? Pull the battery, unbolt the PCM and swap in a replacement? Anyone have a better idea

Thanks
sirrobocop

 

I'd check for power to the coil packs while you're checking for spark. If you have power but no spark then I'd focus on the grounds. Coils need good ground through the ignition system in order to build a charge. I'm not sure how Ford grounds the coil packs, it would either be through a separate ignition control module, like the old EDIS, or through the PCM. Early ignition modules grounded through the mounting points. All of the coil current passes through them. The fact that you had a miss suggests that you were losing a connection or two somewhere.

Grounds are probably the most overlooked electrical problems. Easy to miss when you're just checking for power.

Found this on the internet. A, B, C, and D would be the ground circuits. You can follow them out and eyeball connections and/or see where they go.

https://easyautodiagnostics.com/ford...cuit-diagram-1

 

Thanks BarebonesXL! The ground was not exactly the issue, but I stumbled on the real problem while checking the power at the coil.

This is the stupid chain of events:

1. Misfire on #7, then multiple misfires, followed by a no start condition
2. Replaced coil pack containing #7, but only occasional brief intermittent start condition, followed by no spark on any wire.
3. Used a 12v light continuity tester with key in "RUN" position on the middle (red/green) wire inside the wire loom that plugs into the coil pack

I did not get a light the first time, but I felt like I was having difficulty probing into the connector to make contact. So, I used the probe to peel the orange silicone watertight seal - and I found out there were TWO seals in the socket.

I removed one seal, got good contact with the light, so I plugged the wires in, and got a good restart on the truck. I could feel the truck was still misfiring slightly, especially in gear, although no code was throwing on the ECU. I decided to replace the #7 spark plug wire with one of the spares I keep on hand from a previous change, and problem solved. Restarts, no miss.

Wild guess, the #7 plug wire misfire might have caused the original coil to fry. I'm not sure if the orange silicone seal is supposed to be on the wire loom plug, or come inside the port on the new coil, but somehow I got an extra one in the mix. Most pictures of new coil parts show it without the seal, but here's one with a seal, in case anyone else stumbles here and needs to see what I'm talking about:


Probably would not have figured it out without trying to probe the coil power wire as suggested, since the extra seal does NOT prevent you from re-attaching the wire plug. The locks on the wire plug are both snapped off due to age, and the seal probably forces the plug out of contact just slightly.

Now to rig some zip ties to keep the wire in the coil "just in case".

Thanks for the support everyone!

sirrobocop