Why does an engine run lean when it misfires?
Why does an engine run lean when it misfires?
Common Misconception: When an engine misfires, the cylinder runs lean, not rich, this is because the air to fuel ratio favors air by 14x. Therefore, an engine must be running properly without cylinder misfires to avoid lean mixture codes.
What should the fuel level be for a misfire monitor?
•The Fuel Tank level must be above 15% for misfire monitor operation. It’s not uncommon to be working on a vehicle that’s low on fuel, but if the fuel level is less than 15%, misfire monitoring is suspended.
Do you scan your memory for engine misfires?
Not all misfires are directly translated into DTCs, especially intermittent ones. Yet, it’s a good idea to scan your computer memory because other potential stored codes may help you in diagnosing and fixing your engine misfires (see the box below on Misfire-Related DTCs).
How does the PCM work to diagnose a misfire?
This greatly helps the Powertrain Control Module (PCM–car computer) calculate crankshaft acceleration time. The PCM can detect when a cylinder decelerates (an indication of a misfire), store a Diagnostic Trouble Code (DTC) in memory, and turn on the Check Engine Light.
•The Fuel Tank level must be above 15% for misfire monitor operation. It’s not uncommon to be working on a vehicle that’s low on fuel, but if the fuel level is less than 15%, misfire monitoring is suspended.
This greatly helps the Powertrain Control Module (PCM–car computer) calculate crankshaft acceleration time. The PCM can detect when a cylinder decelerates (an indication of a misfire), store a Diagnostic Trouble Code (DTC) in memory, and turn on the Check Engine Light.
Not all misfires are directly translated into DTCs, especially intermittent ones. Yet, it’s a good idea to scan your computer memory because other potential stored codes may help you in diagnosing and fixing your engine misfires (see the box below on Misfire-Related DTCs).
How can I find out if my engine is misfired?
Some car computers detect misfires by measuring electrical activity [ionization] at the spark plug electrodes. You can retrieve stored Diagnostic Trouble Codes with a code reader (for OBD I systems on pre-1996 vehicle models) or a generic scan tool (for OBD II systems-1996 or newer models; some scan tools can read both OBD I and II).
