Car has code P1131, but I think it's unrelated?

Rasmataz, thanks for the info. But that's not what I need. What would cause it first of all? Why would an instrument illumination fuse being blown have to do with an analog tachometer which should be fed straight from the sensor to the dash, those two don't relate. Why would a tach go from reading correctly to zero when the A/C is turned on? Next how do you check if the A/C relay or A/C clutch relay would be bad?

Just a few minutes ago, I started the car, started right up after acting like it was bad, ad the idle started hunting around and surging, looking for the right speed.

Could all these things trickle down to each other? As in a domino effect? Breaking parts as I go down the line looking for the next part? Looks like the next thing is the O2 sensor, fuel filter and maybe some MAF cleaner.

Engine cranks over if left to sit for a few minutes, then the tach shuts off, then idle starts bouncing, I assume looking for right compensation. I assume the most likely culprit would be vacuum leak, clogged fuel filter/supply/return line, bad O2 sensor, EGR, dirty MAG sensor. Maybe even the IAC. Still doesn't explain the tach shutting off when A/C is turned on.

Will replace fuel filter, check clogs, and clean MAF sensor.

Already turned engine on, listened for leaks, no whistles. Will get some throttle body cleaner and try and clean that as well.

Still don't understand the tac, isn't it it's own system, aeperate from everything else?

I don't that's it either. If that was bad I wouldn't get any spark and engine would either not turn over or shut off if it failed. Us no code for that. I do have an 1131 and a 0102 code. Neither really apply to tach. However those might apply to rough idle and searching for right speed.

So I'm going to try and break this down for as many people out there looking for real answers. 1998 contour kept stalling out and dying, took several jumps over a couple of days. Turned out fuel pump was bad. Took it to ford dealer and had it replaced, warranty. $1100. My price 350, not covered. Still cheaper than the part itself. Brought it home, ran ok for a few days. Stalled out again and brought it home. Battery was shot, replaced it for $100. Car couldn't keep a charge, took alternator in and tested it, yup, bad alternator, $175. Thought bcu. Cables were loose sent power surges back and forth and killed both bcuz that can happen too. Kept searching the Internet. Replaced positive battery lead, cleaned MAF, cleaned throttle body, replaced spark plugs, wires were good, $45. Put car back together, jumped it. Took negative jumper off, tachometer dropped, put it back on, tach came back up. Appears there is a mega fuse, 175 amp, under the air box just below throttle body that was the culprit. That $11 fuse getting ready to blow sent power surges to almost every electrical system causing them to fail. I started out with codes P0102 and P1131. The tach and air flow had nothing to do with this put could have saved $600 had I known to check an $11 part. I still have the P1131 code and now have a P1381 code. Will check VCT next, replace timing belt maybe even replace the O2 sensor and see where it takes me. I'm not an expert mechanic at all. Worked on cars here and there but with pictures I could have walked my 17 yr old daughter thru all of this.