Gonna share 2 pics of my engine and where we think there might be a problem. I couldn't tell you what all the wires are for. Anyways think we are gonna try cleaning this area and see. Pretty much just followed the spark plug wires to the ignition coils to see if anything looked wrong and noticed alot of oil caked up over the years around some wires.

 

That looks like a GM ignition module and a coil pack to me. Similar to what they used in the 90s on all their cars.

 

We need to look up which sensor drives the tach and which sensor drives the speedometer. I believe the vehicles speed sensor drives the speedometer and I believe there is another sensor in the transmission that takes a measurement and converts it to RPMs. I will post later today what is what.

 

Thanks Derf for sending me the information! I have since taken your advice and ordered the chilton's manual that you described from ebay. Fyi they sell newer versions of the Chilton Manual 8419. First one was 91-93, then I saw alot of 91-98, then there there is a 91-02. All 3 labelled 8419. I'm guessing the newer version should have all the diagrams from the older version.

 

You thought wrong.

That's why I specifically suggested the 91 to 93. 93 is the first stable SC2 and SC1 configuration. The book has all the wiring diagrams for both sedans, wagons, and coupes by year. 91 and 92 are trash.

91 98 ends up being useless for mechanical procedures for a lot of things because it includes both first and second generation coupes and sedans, so the descriptions of how to do certain things are usually only for one or the other. The sedans remain very similar but coupes do not in many ways

91-02 covers all three generations of coupes sedans, and wagons. Some mechanical how to stuff is pretty useless since you can't cover three generations of the vehicle for a procedure with a single description when that has changed over the years.

The only redeeming quality of the 91-02 book is it has stereotypical wiring diagrams for OBDI and OBDII versions. They include the PCM input terminal identification, but that usually only comes into play when you've exhausted every other possibility besides whether the signal is getting to the PCM.

With the BCM introduced into the S series in 99, I believe there is a BCM layout as well, but since the problems are almost always with the BCM module itself, these diagrams are not terribly helpful.

I did not know they are all under the same item number. That's a bs thing to do.

 

I should add that another source of the issue maybe one of the connectors at the back drivers edge of the cluster. There are two female harnesses that very tightly grab onto wide copper traces on the IP cluster board.

If they have never been removed, there are extremely difficult to get off. The plastic is dry rotted and there is usually a layer of corrosion lately bonding it to the copper.

Connectors have retention clips at the ends. You can try to save them but they pretty much fall off as soon as you try to loosen them. The key is to remove these connectors without breaking them or damaging the copper traces. The insides of the connectors have matching copper contacts, so you cannot pry in between the two.

It takes a lot of patience to remove them if the car has been a lot of time in the Sun during its life. Keep alternating from side to side. Once you break it loose, take your time alternating sides until it is all the way off. Did not try to pull it off by hand when it is 4/5 of the way. You will not be happy with the result.

Use very fine Emory cloth in a direction parallel to the traces. If you dare. They have a tendency to lift off the board and when they do you're pretty much screwed because they actually tear off.

You are better off using spray electrical contact cleaner and just letting it drain rather than trying to physically contact the contacts to clean them.

You can try sweeping the contacts but because the connectors fit so tightly, this is very difficult.

If you put it back together and get a code 26 for quad driver fault it is almost guaranteed that one of the traces in one of the connectors is not making good enough contact with the trace on the board.

Sorry these suggestions are coming out piecemeal but my brain is not at peak performance as of late so when it comes to mind I post it.

 

The above would make sense if the tach did not work at all. Sorry for that.

There may be a failure on the IP cluster as mentioned by Andy, but everything else should be explored before coming to that conclusion