I have a persistent problem with an engine miss that I can't figure out. I have a 73' 2.0 with F.I. and electronic ignition. The car starts and runs great but about 10 minutes after driving, it begins to miss enough that the car jerks while cruising. It idles fine and doesn't seem to be miss until I start out again. If I shut it off for a few minutes and restart, it runs great for a few minutes but when it gets warmed up again, the miss returns.
I recently changed the coil, rotor and cap and have checked the timing which is good. I removed the spark plugs to check them and #2 & 3 are good and #1 & 4 are black. I changed out the carboned up plugs with good used ones and the same plugs quickly turn black. Is this caused by the FI trigger points? Are #1 & 4 run off the same set of points or do I have a different issue? I have some basic tools like a timing light, dwell meter and multimeter.
Any ideas on how to track down the cause of this miss? It began last fall and seemed to be fixed with the coil change but now that I have it out of storage and am driving, it's back.

Thanks in advance.

Warrenoliver

Yes. 1&4 are fired by one side of the trigger points. Turn the plug on the distributor around and see if the problem moves to the two and three plugs. However, a trigger point problem would generally not fire those two cylinders. I suppose it's possible for one side to be keeping the injectors open, but I've never seen a trigger point fail that way. You could also just swap the injector leads on each side and see if that makes the problem follows the injectors. I would also suspect the injectors themselves. Its very possible for silt in the tank to keep those two injectors stuck open.

I had a very similar problem with my '74 2L where it would cut off and come back on like that, and it eventually progressed to a total shut off. I could cycle the key, release the clutch, and it fired back up for a bit. I dealth with it several times in a typical 20-30 minutes trip.

At one point though, it cut off and would not come back. Wouldn't restart. Had to have it flat-bedded home.

Short version, I replaced the relay plate with a known good one and it was fine again. I am not convinced it was the relay plate as much as it was likely the male quarter-split pins in the plate having contracted and not making good contact with the wiring plug. The one I installed had the pins visually and obviously wider, whereas mine were all contracted. I'm thinking that one of the pins, possibly the main power one, was not making good contact

I recommend removing the plate, cleaning all the contacts and CAREFULLY taking a razor blade to the split pins, bending them outward SLIGHTLY so that they make positive contact with the female barrels in the harness plug. Slather with dielectric grease and reinstall, see if that improves it.

Yeah, I thought about the trigger point failing and it wouldn't inject the fuel so I don't see why the plugs are fouled. If the injectors are going bad or plugged, I wouldn't think it would be the same ones all the time.
BTW, any idea where I can get the injectors cleaned, tested and repaired if necessary?

Thanks for your help.

I'm confused about which "plate" you are referring to. Do you mean the relay board in the engine compartment? If so, which relay controls the trigger points?
About 2 years ago, I had an issue with my relay board being bad and that left me stranded by the side of the road also. I replaced it with a different board and the problem has not returned although my new problem could very well be due to a bad contact on the board.

Thanks for the suggestions.

Warren

Yes.


Dunno. I'm not referring to a relay, and I have nothing to offer on the trigger points. I'm simply suggesting you check and verify the wiring harness connector pins between the engine harness and the replay plate.