1994 Mazda MX-3
1.6L 16V DOHC
Vehicle was parked unused for 9 years under a carport. In 2015, brakes, battery and fuel pump were replaced and vehicle resumed service. Initially, vehicle ran well, but seemed slightly lacking in power. After 6 months, a rough idle was noticed, with the vehicle exhibiting what seemed like an intermittent misfire at idle.
At this point the spark plugs, plug wires and distributor rotor were replaced without a successful resolution to the problem and the misfire grew worse.
Eventually, the Check Engine light started blink codes for the Mass Airflow Sensor and the Throttle Position Sensor. Both were replaced which caused the Check Engine light to stop, but did not have any effect on the idle or lack of power.
Recently the transmission HOLD light began flashing from time to time. This resulted in the Transmission Speed Sensor being replaced, but did not resolve the flashing HOLD light. Transmission fluid was replaced, but still no resolution to the flash of the HOLD light.
Within the last 3 months, an Oxygen Sensor (Inversion) code from the Check Engine light and the engine will not rev past 2400 RPM. At 2400 RPM it will drop RPM’s and then surge back to 2400, drop and surge, drop and surge, until the throttle is released. Sometimes there will be a backfire through the intake. If the throttle is just at 2400, the surge cycle is slow, if the throttle is opened wider, the surge cycle is faster.
O2 sensor replaced, throttle body removed and cleaned, EGR valve tested, checked for vacuum leaks and inspected vacuum hoses, still surging. While the Check Engine light for the Oxygen Sensor (Inversion) has stopped, the codes for the Mass Airflow Sensor (08) and the Throttle Position Sensor (12) have returned.