The Mechanic i took my sammy to told me this and the only code i get is 12 so the ECM thinks all is normal i see there has been 2 caps replaced on the ECM i don't know who or where to have ECM checked or repaired can anyone HELP?

Why did you take the car to the mechanic?  Do you know how he arrived at that conclusion?  Maybe you need to find a mechanic who is familiar with EFI systems.

A defective coolant temp sensor could cause the ECU to think the engine is always cold and that will cause it to richen the mixture and retard the ignition timing, I believe that ECU also gets a "start" signal from the ignition switch, if that were active when it shouldn't be it could be another cause of both symptoms.

i took it to the mechanic because it won't idle,it surges 1200 rpm to 2000 rpm it won't pass emissions test.

Well sounds like a code 12
Check it out
https://www.obd-codes.com/p0012

A 90 Samurai is not OBDII, so OBDII codes do not apply - code 12 in this case means that the ECU is not seeing any faults.

i got a code 14 to flash by disconnecting coolant sensor but i don't know how to check ignition switch for a start signal after engine is running  any help?

Do not assume that the coolant temperature sensor is good because the ECU does not report a fault - the ECU will only tell you if it is shorted or disconnected - it won't tell you if it's saying cold when the engine is hot - you need to test it.

Also you need to check for the start signal at the ECU, not at the ignition switch - the start signal comes from the wire that runs from the ignition switch to the starter solenoid to pull the solenoid in - it is connected to the ECU so that the ECU knows when the engine is being started, it should be at 0V (relative to chassis ground) whenever the engine is not being cranked.

There should be a service manual at Acks FAQ with details on what resistance the coolant temperature sensor should show at various temperatures.

Ok ill get specs on temp sensor & trace the solenoid engage wire to the ECU make sure 0 volts to ground when engine is running got it Thank You for your help!