91 Lx Ignition Question

The spark advance will jump all over the place with the SPOUT in. That's the computer controlling the spark timing.

The 7 three times in a row while in cylinder balance test mode suggests low power on cylinder #7. Start swapping things like spark plugs, spark plug wires and injectors from other cylinders to cylinder #7 to see if anything changes, No changes, then be prepared to do a compression test. If the failure follows a swapped component to a different cylinder, you have found the culprit that cause #7 cylinder to fail.

The code 18 bothers me, and I have lost track of what you have replaced.. You have swapped a lot of stuff, so a re-listing of the parts you have replaced would be very useful at this time.

I suggest that you start at the top of this list and work your way downward.

Replacing the TFI would be the next logical step to eliminate the code 18. If that does not fix it, then the computer is the only thing left to cause code 18.

If I correctly understand your explanation of the resistance testing of the TFI & SPOUT wiring, it is OK.

The failure of the cylinder balance test with it pointing to cylinder #7 needs to be resolved. You will probably want to use the noid tester to check that cylinder.
If it passes the noid test, that leaves either a bad spark plug, bad spark plug wire, cap, fuel injector or no compression. Swap the items around to a known good cylinder and run the cylinder balance test again. If it follows the swapped item, you have found your culprit for the cylinder balance test failure
If the noid test does not pass, that leaves the engine fuel injector harness, 10 pin connectors, main wiring harness or computer. Of all the items in this group, the 10 pin connectors, and the computer are most suspect. I have a procedure to test the injector wiring from the injector socket to the injector pin on the computer harness. If it is needed, I will post it later.

Once you have cleared the code 18 and the #7 cylinder failing the cylinder balance test, start working on the idle. Don’t jump around and try to fix the idle problems before fixing the codes, you’ll just confuse things and make the troubleshooting process more difficult.

I have the same problem I'm not getting spark signal. I tested pip, tfi, and coil and everything is good. When doing my resistance test on the yellow and lt green wire I get nothing. But when I do a continuity test between tfi and computer it is good. I jumped the yellow and lt green wire straight to my negative side of my coil and get spark. What could this be. Thanks