1993 Ford Mustang RPM/ Check Engine Light/ Acceleration

Electrical problem
1993 Ford Mustang 4 cyl Wheel Drive Type unknown Automatic 150000 miles

Hello:

My RPM Gauge is not working. The needle moves sometimes, but most of the time it just remains dead with no movement. In addition, my check engine light remains on and no mechanic I go to seems to have answers. Also, my acceleration is totally weak. The car goes through alot of stalling during acceleration and then it will suddenly accelerate with the big thrust. No smooth acceleration process here, although I have a new transmission. Please help. I've been to three mechanics and they say the problem is fixed, take my money, and everything is still the same.