Signs & Symptoms of a Bad Throttle Position Sensor on an Mx3

Written by jonathan lister Google
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Signs & Symptoms of a Bad Throttle Position Sensor on an Mx3
The Mazda MX-3 combined a customisable body with a racing style engine. (sports car image by Jake Hellbach from

The Mazda MX-3 was produced from 1991 to 1998 and featured a highly customisable body style and choice of three engines. This high-performance vehicle attracted the eye of street racers and car enthusiasts alike due to the vehicle's durable components and ease of customisation. Engine problems did occur with the vehicle, however, with issues like throttle position sensors affecting the MX-3's fuel economy, engine performance and transmission function. Drivers experiencing such symptoms should take the vehicle in for service immediately to avoid potentially expensive damage.

Engine Buck and Jerking

A faulty throttle position sensor (TPS) will send erratic signals to the Mazda's engine control unit, which will be unable to determine the position of the throttle. As a result, the driver will experience engine buck where the timing of the MX-3's engine is irregular. The engine will cause the vehicle's fibreglass body to shake and lurch forward. This is called "idle surging," and occurs as the ECU cycles through positions in an attempt to correctly locate the throttle.

Transmission Problems/Engine Idle

Mazda MX-3 models with automatic transmissions may experience an inability of the ECU to change gears because of the lack of throttle positioning. Drivers will also experience a rough idle and hesitation when the vehicle first accelerates due to the fuel-air mix running rich through the engine. The MX-3's three engine options (1.5L I4, 1.6L I4 and 1.8L V6) were built for speed and performance and as such are highly susceptible to the timing issues associated with air-fuel mixture.

Engine Stall/Engine Surge

A failing TPS will cause the Mazda's engine to run lean because the engine control unit believes the throttle is in the open position all the time. This will result in more engine stalling when the vehicle is idling. In addition, the driver will also experience a sudden surge in speed when the vehicle is travelling at high speeds. As the Mazda is a performance vehicle (0-60 mph in 8.4 seconds) this particular symptom can pose additional hazards for the driver as control of the vehicle may be lost at higher speeds.

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