Lack of Power. If the ECM is reading high vacuum, it assumes the engine load is low, so it cuts fuel injection and retards spark timing.This leads to excessive fuel consumption, poor fuel economy, and possibly detonation. Poor Fuel Economy. If the ECM is reading low or no vacuum, it assumes the engine is at high load, so it dumps in more fuel and advances spark timing.So, how will you know that your MAP sensor is going bad? Here are the key problems to look out for: If the MAP sensor goes bad, the ECM can’t accurately calculate engine load, which means the air-fuel ratio will become either too rich (more fuel) or too lean (less fuel). Sometimes, engine heat “overcooks” the MAP sensor's electronics or cracks vacuum lines. MAP sensors fail by getting clogged, contaminated, or damaged. MAP sensor problems could trigger a DTC and check engine light.