I have a 1996 Ford F150 with the crazy 5.0/302 where the plenum covers one side of the motor. Started to misfire but didn't show engine light till later that afternoon. Its saying the #4 so knowing from my experience and seeing some open wire from rodents. I pulled the plenum so I can just go in there and check the wires.My thoughts are to fix what I find and apply a heavy coating of liquid electrical tape to hopefully avoid this for a good time. Now here is my confusion comes into play. The #3 injector is showing the bare wire damage but the rest look fine. So my thinking is why the #4 is the problem when nothing has been chewed on but yet the #3 does but not misfiring? Does this make any sense? Truck was running great before this came about. Seeing I can't work on it till my next day off so its rides to work till I can get back in there and work on it. My thinking is vacuum everything nice and clean and pull the whole harness up and go completely through it. If needed maybe even look into replacing the harness? That's if its possible to find a new one? Since it going to be easy to access, I am already going to replace plugs and wires. I also have a lifter makes some noise over on that side as well. I'm not experience with adjusting so I might leave that alone. It hasn't affected it and doesn't get any louder when driving. It's mostly heard when idling. It sat for about a month so that started when I first cranked the motor.So what do you guys think about the misfire issue? Thanks

 

Id put some di-electric grease on the connections and snap them together too.. Also knowing that cylinders 1234 are on the passenger side and 5678 are on the drivers side for referrence too

Theres ways to determine whats good and bad with a DVOM so on the ECU theres 8 seperate trigger wires aswell as only 1 main power feed from the ecu branched off to test each or the suspected areas for continuity and open faults..........If you suspect flip flopped plugs on 3 and 4 the VOM test from the EEC plug will tell it through a continuity circuit trace........

Noid lights help alot too;-..
Sometimes the problem is either a coil or a wire itself but seeings its suspected mice if wires short together bad things happen with-in the ecu too.....Hence the noid lights...

You can use a DVOM too ...I use one that measures hz plus bluetooths the results to my phone so I can still see the results even when I cant be there to see the screen.....

Good Luck

 

I would have to wait till next check to get that tool. If i remember from that ( over 10 yrs ago) I had the same problem but it was taken to a shop so I didn't get to see what it looked like but was told a rodent had got into the injector wires. From what I am seeing on the #3 wires , its has been chewed on. It's like they chew the cover off. Hell it could just be a faulty wire or plug but seeing the bare wire is what made me remove the plenum to get full access to all of them.I was just thrown off by the wire not relating to the problem was the only one damaged. Thanks

 

Pull the #4 spark plug and inspect.
How does the plenum look? Look at #7,#8, #3 and #4. If you have a large build up of oil/carbon, it could be because your PVC is connected at the back of the plenum. Usually causes issues with #8.
Ford TSB says to move the PVC to the middle of the plenum.
Just something else to look at.

 

I will take a look at the plenum in the morning but everything on the intake look the same. I just wasn't sure if the #3 wire to the injector was effecting the #4 since 3 is showing some bare wire and I am going to fix that in the morning as well. I seen a couple of the wiring diagrams on injector injectors and i will admit they confuse me. I am going to reroute some of the tubing and wiring from behind the plenum so they don't cover the bolt that gave me a huge issue when removing it. Its a shame when Ford 302 are simple engines to work on and they dumped all this crap on top of them with fuel injection. Darn thing covers one side of the engine and fuel injectors. Rodents seem to like the tunnel to hide in. Thanks for the help guys.

 

Update its running good now.I was wrong on which injector connector had wire exposed. It wasn't #3 but #2. I cut,cleaned and reconnected the wires and I replaced plugs and wires. Wasn't really any difference in the plugs so who was the problem will remain a mystery. The rest of the injector wiring looked really good. Checked plenum and was was a little cleaner on the number 4 side but again, no real huge difference. Its running nice and smooth and I'm happy with that. Thanks guys for the help.