ASE A8 Engine Performance, checked for 2026

Incorrect: The MAP sensor reports manifold pressure, not throttle angle, so it cannot create a jump in the TPS trace.

Correct: A sudden step in TPS voltage at one throttle angle points to a worn spot on the sensor's track; the signal should rise smoothly through the whole sweep.

Incorrect: The engine control module only reads the signal; a step tied to one blade angle points to the sensor, and the module is condemned only after the sensor and wiring test good.

Incorrect: The pedal sensor has its own signal circuits; a pedal fault would not appear as a step in the throttle position trace.

Incorrect: The actuator motor moves the blade; a bad motor shows as sticking or a position error, while this step sits in the position signal itself.

Incorrect: Cap and rotor wear adds a gap and raises firing voltage, but the spark still jumps, so a spark line would still appear.

Incorrect: Carbon fouling bleeds energy to ground across the insulator, giving a low firing line, not a high one.

Correct: With the secondary open the coil's energy has nowhere to go, so the primary flyback climbs far above normal and no spark line forms.

Incorrect: Low supply voltage weakens the coil charge and lowers the flyback peak, the opposite of a 450 V spike.

Incorrect: A plug wire shorted to ground gives the spark an easy path, which lowers the firing voltage instead of raising it.

Incorrect: A weak fuel pump causes lean stumbles under load; it changes neither exhaust backpressure nor manifold vacuum.

Incorrect: A bad coolant temperature sensor skews fueling, but it cannot create 5 psi of backpressure in the exhaust.

Correct: High backpressure ahead of the converter plus vacuum that sinks while rpm is held steady is the classic sign of a plugged converter trapping exhaust.

Incorrect: A restricted air filter starves the intake but does not raise exhaust backpressure, and vacuum would not fall away at a steady 2,500 rpm.

Incorrect: An intake vacuum leak gives low, steady vacuum at idle that improves with rpm, not a reading that drops while speed is held.

Correct: An open purge valve feeds fuel vapor into the manifold; at idle that vapor is a large share of total intake, so trims go negative, and at 2,500 rpm the extra airflow dilutes it toward zero.

Incorrect: A vacuum leak adds unmetered air, which drives trims positive at idle, not negative.

Incorrect: A restricted regulator return raises fuel pressure at all engine speeds, so the rich correction would stay at 2,500 rpm instead of fading.

Incorrect: A coolant sensor reading cold adds enrichment at every speed, so the negative trims would not clear up at 2,500 rpm.

Incorrect: An exhaust leak ahead of the sensor pulls in outside air and reads lean, which pushes trims positive.