I have a manual 5peed 2004 Relliart Mitsubishi and it stops everytime it hits 3rpm then i would go up one speed then its ok until it hits the 3rpm again i would increase again. according to the check engine, the problem is the speed sensor. I tried locating the speed sensor but can't seem to find it. Do you know where the speed sensor's location and do you think speed sensor will fix the issue?

 

Not sure but it is on top of the tranny underneath the intake air hose

 

it's on the differential housing on the tranny under the shifter cables, to remove it, you need to take the metal wire clip out, to get the connector off and it's held in by a 10mm bolt if i remember correctly. your car is in limp mode, does the speedometer work?