1989 F250 with a 460

So I've been trying to figure out why I have stuttering and stumbling when trying to accelerate fast. I got a spark tester and used it on the wires. Cylinder #2 is a weak spark. It fires fine at idle but when you hit WOT, it doesn't fire. If you rev slowly it does fine. It also randomly doesn't fire when the rpms drop down from revving. None of the other cylinders do this.

All the wires are brand new, less than 3 days. I switched wires and the issue was still there. I also grabbed some old wires to double check and it still did it. The rotor and distributor cap are about 3000 miles old. I checked the contacts inside and they appeared to be fine. I lightly hit them with some sandpaper to be sure. The coil was replaced when I changed the rotor and distributor cap. I also tested the coil using a ohm meter per Haynes manual and it was with specs.

It also did this before I changed the coil, rotor, wires, plugs, and cap. I assume it's something that wasn't changed? What else is left related to ignition? The ignition control module and that's it?

 

Have you tried checking the gaping of the plugs?

 

The tester I am using is one that you plug into the boot and then short to a good ground. There are no plugs being used.

I used one that was open and the spark jumped a gap so you could see the actual spark. I then used another tester that had an enclosed light. The tester was left in the same location and each cylinder plug wire was tested. Every cylinder except for cylinder 2 worked fine. Number 2 would not fire when blipping the throttle to WOT and would randomly not fire when the rpms were dropping down from say 3k. The spark in the gap tester did not look as strong as the other sparks. I changed the wires to see if that made a difference and it did not.

The only thing I can think of is that the spacing between rotor and cap is off or that there is something wrong with whatever tells the computer to fire and it is not firing the cylinder when it should. Other threads I've found on other sites say to change the crankshaft position sensor as it is not working correctly. I think something is wrong with the distributor or whatever electronics/gears are used in it.

Plugs were all removed and gap set to 0.044" on Tuesday. 0.044" what is in the haynes manual and the sticker on my air filter box says gap 0.042" - 0.046"

 

Just for grins.........is the #2 spark plug wire (on the distributor cap) located near where the pip sensor is mounted inside the distributor ?????

Spark jump there maybe ????

Bob

 

I don't get it?id you suspec the spark plug? Switch plugs wih another cylinder or put a new plug in.

 

Reluctor wheel in the distributor rusty at one point, something stuck in it? one for #2, that one lug damaged, bent misshapen perhaps?

 

@dad50+
No, I'm not using spark plugs. I am using a tester that you plug the boot into and then connect the tester to ground.
Like this:

@bob
No, I ran the wire several different ways. The wire comes off the cap and doesn't go down by the body of the distributor at all. I also checked it last night in the dark trying to see if I could see any loose sparks in the engine bay. There were none. I also checked out all my grounds real good and repaired a few rusty/corroded ones for ya.

@danr1
I think it's something like that. I found a few posts on other car forums saying it was the crankshaft potion sensor. We don't have those, we have something called a PIP (profile ignition pickup) that reads from the distributor then sends a signal to the ignition module. See CounterPoint Archive 2004 - 2006 - Wells Vehicle Electronics volume 8, issues 2 and 3. Good readin right there. I just need an O'scope now....I've always wanted one and it looks like I just got my excuse.

When I get enough money I'm going to pull the distributor out and see what's up. I'll change the cap too just to make sure it's not something stupid like that before I take stuff apart.

 

You need to cross this post with the other post you have here.

All of this could be vacuum related ........ and needs to be corrected before you spend any money of an oscilloscope (they are pretty cool though )or other diagnosing tools.

Since I don't have a 460, is the #2 spark plug wire the longest wire in the set.
If you're running lean because of a incorrect or leaking vacuum system you will get a weak spark on the furtherest wire from the dizzy.

Do the vacuum leak system check(s) repairs we discussed in your other post.
I'll bet it cures this spark issue and stumble issue you've got going on.

Bob