Electrical One of a kind spark issue?

Howdy y’all!
First off I want to say thank you to all the members here who have unwittingly helped me work on this car while I’ve been stalking threads.
Now onto business. I have an efi 5.0 in my 87 ‘stang with enough mix & matched upgrades to give you a headache. Out of the blue, after driving it for a while since replacing all ignition components besides the dizzy, (plugs, wires, tfi, cap & rotor, coil) it starts idling rough, and I don’t think it could have drove anywhere, didn’t try. Closer inspection reveals I am getting no spark to #1 plug at the DIS cap. With the engine running I can touch the tower barehanded. I didn’t know this was possible, and apparently neither did google as I can’t find anything remotely similar. The only thing I can think of is that the MSD dizzy is shot, but that still doesn’t make much sense cause if the magnets were going wouldn’t it be erratic misfires and not a steady #1 miss???

No codes besides #34 which is the egr. Which is blocked off with lmr’s kit.

Verified compression & that all components are indeed working. Ohm’d all wires to tfi and coil. Swapped #1 & #6 wires placements at the cap to verify the tower was the problem. Timing set at 12°.
The dizzy is the only thing that bothers me, as I don’t know how to test it. But nothing was broken inside. Gears fine.

Can the computer cause this?? I’m going to pull it later and check for breaks anyway.

So far it has stumped all my mechanic family members and our sanities are going to go out the window soon if we keep dreaming about this crap.
At this point the only option I can think of is getting it scoped.

Recapping, it was driving absolutely fine. One morning a few days ago started it up and no spark to #1 at the dis.

Sorry for the long-winded ness of the post, I appreciate any help you might have. If you want a list of parts... I still don’t know all it has internally. As for ignition components, MSD dizzy, I don’t have a spare and would prefer to avoid spending money until I’m sure of the problem, motocraft coil, select tfi, (and MSD spare) streetfire cap & rotor (brass)

If I missed anything please let me know.

- Wolf out

Steel1 said:

In my experience aftermarket ignition parts can be problematic on these cars especially TFI.

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I 100% agree. Anytime you combine a stock computer with aftermarket sensors you’re asking for parameters to not line up. I just found it odd that both TFI modules would cause the exact same problem after it had been running fine.

Steel1 said:

So you tried 2 different tfis , were both of them aftermarket ?
I've even had intermittent issues with just an aftermarket shutter wheel, change to oem...solved.

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I’m hesitant to blame the tfi at this point, however you just “sparked” something. I wonder if the pickup coil and shutter wheel are the culprits here. Still seems very odd, but more plausible than anything else I can come up with.

Steel1 said:

If aftermarket could certainly be possible.
Any check engine light, could pull codes to narrow it down.

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It’s an msd pro-billet dizzy. But even stock parts wear out.
As I mentioned the only code is 34, which I set off.
87, so no check engine light.

UPDATE: Would be cool if this thread could be marked as solved to help others.

So, today i pulled apart the distributor and slapped in the new pickup coil i ordered. PROBLEM SOLVED. The aftermarket TFIs are both fine. Spark to #1 cylinder restored. The hardest part of the change was getting the dizzy gear off without breaking the end of the rod. Ended up using a socket slipped over the end with a two-leg puller.
As a note if you ever need to take apart your MSD dizzy, be VERY CAREFUL with the shutter wheel. They are thin aluminum and bend easy. I can only find one site that sells this particular one and its $70.

- Wolf out