88 Ranger 2.9l missing spark

[LittleDevinBro]

I have an issue with my ignition system. My truck wants to run great but it keeps missing spark. I hook up a timing light and all spark plug wires miss. So I think it has something to do with the distributor or the ignition coil. I have replaced the distributor like four times and it keeps doing the same thing. I have also replaced spark plug wires and the ignition coil. I’m not sure what else to check other than ground wires. I wanted to come on here to see if anyone has any ideas.

If you get in the truck and start it it will run okay but then it just jumps rpms on the tacometer. What I mean by that is it will drop rpms suddenly and randomly. It drops anywhere between 100-400 rpms. It does it most when high rev and righ rpm. Guessing because the rotor is spinning fast and it’s producing more spark.

I have tried to insulate the cap more and it doesn’t make a difference.

Is there anything else I’m not thinking of that can cause a miss spark on all 6 wires or should I check ground wires again?

I did also replace the connector to the ignition module that’s connected to the distributor. I did that in between a couple distributors so I know that’s wired correctly.

Let me know if you have any other questions about what I’ve tried so far or if you have any ideas.

 

[franklin2]

I just had a problem with my 2.9. It would not start very well, but once running would run fine. As it got colder and colder, it took more cranking till it would not start at all, just crank. I found I had a voltage problem to the coil +. This is the same circuit that also feeds the TFI power.

I found I had voltage at the coil +, but when cranking, it went a little to low and would not fire the coil. What sealed the deal that it was the problem, I took a jumper wire and jumped the coil + wire directly to the battery +. Fired right up after I cleaned the wet sparkplugs off. If you want to try the jumper wire to the coil +, that could tell if you have intermittent power problems to the coil.

In my situation I cheated. After all that troubleshooting (a week on and off) I was burnt out. So what I did, I added a little bosch type relay to feed the ignition. I used the original wire feeding the ignition circuit (it comes from the firewall on the driver's side) and used that to fire the relay. I then went from the battery through the relay and then to the coil circuit. Fires right up everytime, been that way for about a year now. Not sure what the original problem was, be assured it's still there, I just went around it.

 

[LittleDevinBro]

I appreciate your comment. I’m not sure what to do to be honest. I’m thinking about using your advice and start using a jumper wire to see if I can narrow down a bad ground or power wire.

All I know is that the truck runs great and then randomly it will miss spark(at the same time time drop 100-400 rpms) and then the computer tries to compensate for it and doesn’t run right after that. But it if could stop misfiring then the truck would smooth idle and run great. Has good power when it doesn’t start losing spark.

 

[SenorNoob]

Guessing you changed the TFI when you changed the distributor? What about ground on the TFI? I've heard adding a ground wire cane make a difference.

 

[franklin2]

There is also a major large ground on the 2.9 that goes from the coil frame, through the loom, and bolts to the side of the tall aluminum intake. You can loosen those connections and clean them up, the one on the coil base likes to rust and the one on the intake likes to get that white corrosion on it. It's a big fat black wire.