ASE L1 Advanced Engine Performance Practice Test 2025 – Complete Exam Prep

When the exhaust is clogged, the manifold absolute pressure (MAP) voltage reading tends to increase, which corresponds to a high reading. This occurs because a blockage in the exhaust system inhibits the flow of exhaust gases, causing back pressure to build up. As the engine struggles to expel exhaust, the overall pressure within the intake manifold can rise due to a reduction in engine efficiency and an increase in the vacuum levels. This results in the MAP sensor detecting a higher pressure signal, which translates to a higher voltage output.

This scenario reflects the engine’s inability to expel exhaust gases effectively, which can skew the readings from the MAP sensor. In a normally functioning system, the MAP sensor provides crucial data to the engine's control module for managing fuel delivery and ignition timing; however, with a clogged exhaust, this data becomes misleading, leading to potential performance issues.