1987 Nissan Truck engine rev

Hi Bcrapson,

Thank you for the donation.

There are 2 different symptoms and

1. Engine rpm would go up to the specified range and maintain as if you are holding the speed. Wide open throttle could not be achieved due to too much slack in the accelerator cable or something is stopping the throttle valve from opening fully. Check if there is any foreign material in the Mass Air Flow restricting the volume of air going in.

2. Engine would surge or misfire as if cutting off and on. This would be due to sensor out of adjustment or not properly installed. If the Throttle Position Sensor is out of adjustment, it would cause this.

There is a self-diagnostic system which you can use to to check for fault codes.

MODE 3: SELF-DIAGNOSIS
The ECU constantly monitors the operation of sensors and actuators, regardless of ignition key position. When a malfunction is suspected, the information can be retrieved from system memory by turning the diagnostic mode selector to the "ON" position on the side of ECU to Mode 3. See Fig. 3 .

When properly activated, the Red and Green LED lights will flash appropriately to signal the code number of the malfunctioning part(s). First the Red light will flash and then the Green light will follow. Red light flashes refer to number of tens in the code number. Green light flashes refer to number of ones in the code number. All codes are classified in 2 digit numbers. For example, if Red light flashes once and Green light flashes twice, code 12 is detected. All codes are stored for 50 ignition starts from the time the malfunction is last detected. A code of 55 indicates no problem in components monitored by the ECU.

When diagnostic code(s) are obtained, refer to the SYSTEM INSPECTION TABLE that applies to the application of vehicle and perform the test that it refers to. If no diagnostic codes are obtained, define the driveability symptom and refer to the DRIVEABILITY INSPECTION TABLE that applies to that vehicle (perform Mode 4 first). There you will find a list of common driveability symptoms, find the symptom that your vehicle is exhibiting and check all the components in that column as well as any tests listed.

If engine cranks, but fails to start, crank engine more than 2 seconds prior to starting self-diagnosis in Mode 3. Do not erase stored memory codes prior to self-diagnosis (Mode 3) or intermittent malfunctions will be lost. Stored memory is lost if battery is disconnected or if Mode 4 is selected after Mode 3.