Odd stumble
 

Today went to get ice cream with my son, and on the way home the engine stumbled a little bit while I was going threw the roundabouts. I was a bit low on gas, so I got some more. But it still stumbled a little bit. Pulled it in to the shop and started it up. A few times it cut out, put still kept running. Once it actually stalled. I checked the fuel pressure, got about 40 KOEO and about 32-33 KOER. So I'm thinking it's not fuel. I then took a heat gun and heated up the coil, but no stumble.

Then I pulled out the big guns.
Attachment 1541

And this didn't find anything. The engine stopped stumbling. So, does anyone have any idea where to look? I'm thinking this is in the ignition system. A few months back I replaced the plugs, distributor cap and rotor. Not sure if the coil is getting bad, didn't change when I heated it up. perhaps coil wire.

Started to do it again. I believe this is electrical. The tank is full, and I have fuel pressure. Also noticed the RPM gauge drops to zero and then jumps right back up each time it stumbles. But the radio stays on. Seems to be a loose wire. Going to go over the battery connections at the block and starter tomorrow.

Fuel filter? Almost sounds like a fuel delivery problem to me

I thought that, but fuel tends to be more loss of power, this is a shut off, then right back on again. But I may check the filter just for giggles.

I've experienced a stumble with a plugged fuel filter before

So have I, but it wasn't like this. But I will check it anyways. This is just like a switch is flipped off, and then right back on.

Reseat the connector on the crankshaft position sensor. With the tach dropping to zero, something is telling the PCM to stop firing. The PCM relay is a possibility too.


Oh, I just re-read your post, I'm not sure it will have a crankshaft position sensor with a distributor.

That was one of my first thoughts as well. Exactly what a bad crank sensor would do. But I have a distributor, so no sensor. About 6 months ago I replace the distributor cap and rotor.

How about the pickup in the distributor?

You talking about the center rotor? I replaced that. What ever it is it seems to be killing spark for just a moment. Kind of thought a bad coil, but I heated it up with a heat gun and no change. I wiggled the coil wire and no change. I tapped around on things, no change. It seems to happen when it feels like doing it. I'll do some digging around today. I just need to find what is loose. Seems to only happen after it's warmed up a bit. A friend suggested checking the battery cable at the starter, he's seen several Ford trucks do this and he found a corroded cable at the starter.