i got a 95 civic with a b16a. its obd1. the check engine light is on now, and the motor is making a humming sound. if i try and rev the car at all, the motor will not allow me to rev beyond 3500 rpm's. when the rpms do climb to 3500, it sounds like its tacking out, or hiting rev limiter. i can drive the car through every gear, just as long a i shift before 3500 rpms. thecar is slow getting to that point now too... WTF ???

 

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try checking out if your VTEC Oil Sending unit (VTEC Pressure Switch)is getting twelve volts or if it has continuity between the two connectors.
Also, the connector for the Oil sending unit is compatible with the coolant tempature switch. Triple check it.. you did do a swap right?