Diagnosing PCV Valve Stuck States via Reverse Engine Spin
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Solution Overview
Problem
Existing methods for diagnosing the functionality of a positive crankcase ventilation (PCV) valve are prone to noise issues due to varying engine loads, requiring complex noise reduction algorithms and are not effective in distinguishing between a stuck open or closed valve.
Innovation Solution
A method involving spinning the engine in reverse and forward directions without fuel or spark, using pressure and air/fuel ratio thresholds indicated by sensors to diagnose if the PCV valve is stuck open or closed, thereby determining its functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If blow-by based diagnostics approach is used to diagnose PCV valve degradation, then PCV valve degradation can be determined, but significant noise issues occur due to various engine loads requiring computation intensive noise reduction algorithms
Solution Approach 1:
The patent extracts the diagnostic measurement from the noisy operating environment by using a controlled test mode. The system isolates the PCV valve functionality by creating a specific test condition where the engine is operated in a controlled manner, separating the valve performance measurement from the confounding noise of normal engine operation including friction, barometric pressure changes, AC compressor load, and alternator load.
Solution Approach 2:
The patent changes the operating parameters to a specific test mode that facilitates accurate measurement. By transitioning to a controlled test operation with specific throttle positions, engine speeds, and duration parameters, the system creates optimal conditions for measuring PCV valve degradation without the noise of normal variable engine loads.
2Measurement precision
If blow-by based diagnostics approach is used to diagnose PCV valve degradation, then PCV valve degradation can be determined, but the approach is not effective in distinguishing between stuck open or stuck closed valve
Solution Approach 1:
The patent segments the diagnostic process into distinct test phases that isolate specific valve failure modes. By dividing the diagnosis into separate test sequences with different throttle positions and duration parameters, the system can independently evaluate whether the valve is stuck open, stuck closed, or functioning normally, preventing confusion between different failure states.
Solution Approach 2:
The patent uses inverted diagnostic logic by observing system response under controlled test conditions rather than attempting to directly measure valve position. By controlling the test parameters and observing the resulting engine behavior, the system infers valve status indirectly, which allows differentiation between stuck open and stuck closed conditions that direct measurement might confuse.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces engine complications by accurately diagnosing whether the PCV valve is stuck open or closed, preventing issues such as surges and degradation, and allows for timely maintenance.
Implementation Method 1
indicating pressure in a crankcase ventilation tube via a pressure sensor, the crankcase ventilation tube fluidically coupling the crankcase to an air intake system configured to draw intake air into the engine
Implementation Method 2
indicating an air/fuel ratio in the intake manifold of the engine via an intake air oxygen sensor
Data Source
AI summary
Methods and systems are provided for diagnosing a positive crankcase valve during a vehicle key-off event. In one example, a method may include controlling a fluid flow from a crankcase of an engine to an intake manifold of the engine via a positive crankcase ventilation valve, and indicating whether the positive crankcase valve is stuck open responsive to spinning the engine unfueled in a reverse direction, and indicating whether the positive crankcase valve is stuck closed responsive to spinning the engine fueled but without spark in a forward direction. In this way, functionality of a positive crankcase ventilation valve may be diagnosed effectively during key-off conditions, which may prevent or reduce engine complications arising from a stuck open or stuck closed positive crankcase valve.