When driving down the road as I ge5 close to work or home (18 miles or so) I have been seeing a stumble while driving down the road under mild to moderate load. Any ideas?

Fuel filter

I have cased this problem before. Check plug wires also. I had a friends bronco acting up going over Monarch Pass. We rebuilt carb and changed fuel filters helped some, Then changed plugs, no help, new better plug wires fixed problem.

Alright so the green machine's slight stumble on load has changed quite dramatically. I can say for sure it is not the fuel filter, distributor, plug or coil wires as all of those are brand new.

Drove it to work on Friday and the slight every now and then stumble was there on the way to work getting worse as I got there.

On the way home it was ok to start with a every now and then cut out stumble but by the time I got to the exit at 6th and Kipling I am pushing in the clutch and out and pumping the throttle to get the revs up and push thru the stuttering dead spots. On the off ramp I have a prolonged dead spot and when it kicks back in I get the mother of all backfires. So obviously getting fuel is not the problem.

I nurse it off the road and as I pull off it is dead. The starter just spins. Doesn't even pretend to want to start. I pop the hood. Wiggle various ignition related wires and connections...nothing. At this point because it is Valentines day and I need to get home to pick up the kids I toss a hail mary, grab a wrench and bang on the coil, ignition module on drivers fender and the alt module on the pass firewall...Frickin thing starts right up. Get most of the rest of the way home and it starts the stutter dance that gets progressively worse until it once again is dead. This time in the left hand turn lane. Fantastic. I do the dance again and eventually get it to start and hammer the poor beast angrily the whole way home.

Here is something that doesn't make sense to me.

When it is dead the flashers, hazards, and the heater fan don't work but the starter and headlights do? I just don't get it

What year is it? Any charging system upgrades? Any wiring upgrades? Heater and hazards work fine otherwise?

[quote="Viperwolf1"]What year is it? Any charging system upgrades? Any wiring upgrades? Heater and hazards work fine otherwise?[/quote]

1974
no wiring upgrades
Only charging changes would be a new alt several years ago
Everything works fine otherwise

Only odd electrical thing I have seen which has been there for at least the last 10 years is that the dash lights not in the instrument cluster are on when the lights are off and the key in the ignition and turn off when you turn the headlights on. The instrument cluster lights work as expected

Is the new alternator a stock 1g or a 3g?

The alt was a direct replacement for the old one

I would think your battery and alt are good if you can spin the starter.
It's sounds like a ground/fuse issue almost since some work.
Do the lights start to dim when it starts to have the issue. In the cab or outside.

The ones that work when the issue happens do not appear to dim

I was first thinking it might be a problem with the fusible link (reason for the alt questions) but now it sounds more like you have some creative wiring going on.

You might check the power supply to both your ignition coil and spark control unit to see were the power stops. You might have a bad ignition switch.

Yeah it seems like that to me. I'll go Thru and see what I can find...

Anybody have any thoughts on that t3 bronco harness?

And of course now it isn't having the issue. Drove it around the block for 30mins to get it hot. Hard to ts it when it isn't happening.

I might just throw parts at it starting with a harness, ignion mod, coil, ign switch just for peace of mind

Figures...I unconnected and reconnected all the ignition wire connections on the coil and module and the issue is gone at least on my last test drive