Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
tell me how it runs out on the road......do you feel the missfire?please explain
It runs very well on surface streets and on the freeway. even better sence I have been replacing parts. I cannot feel the missfire at Idle or during acceleration. I would never know there was a misfire of not for the check engine light. This car passed smog 4 months ago.
i would think you may need to check the fuel pressure..these must have no less than 60psi at all times..a weak fuel pump can cause this code to show
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CIRCUIT DESCRIPTION When you turn ON the ignition, the vehicle control module Vehicle Control Module (VCM) energizes the fuel pump relay which powers the fuel pump ON. The pump remains ON as long as the engine is cranking or running and the VCM receives reference pulses. If there are no reference pulses, the VCM shuts the fuel pump OFF within 2 seconds after the ignition was switched to the ON position or if the engine stops. The VCM also turns ON the fuel pump for 2 seconds when you turn OFF the ignition.An electric fuel pump pumps the fuel through an in-line filter to the fuel meter body assembly. The pump attaches to the fuel level sender assembly inside of the fuel tank. The fuel pump provides fuel pressure above what is needed by the fuel injectors. The pressure regulator keeps the fuel available to the injectors at a regulated pressure. Unused fuel returns to the fuel tank by the fuel return pipe.
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CIRCUIT DESCRIPTION The Crankshaft Position (CKP) sensor is the primary input to determine if misfire is occurring. Engine misfire is detected by monitoring crankshaft speed variations between cylinders. If a crankshaft deceleration occurs during a combustion or power stroke, the control module will compare this change in crankshaft speed to the previous cylinder. If the crankshaft speed change is more than a maximum allowable speed, the misfire is detected. Misfire may occur in a specific cylinder or in all cylinders randomly.When an engine is misfiring, brief decelerations in crankshaft rotational speed will be detected by the CKP. The control module determines which cylinder has misfired based upon the Camshaft Position (CMP) sensor input. Misfire data is stored for each cylinder in separate accumulators. After 100 combustion events, the misfire totals are compared to a calibrated maximum number. If the misfire is excessive, this Diagnostic Trouble Code (DTC) will set.CONDITIONS FOR RUNNING THE DTC IMPORTANT: If start-up ECT is below -7°C (20°F) , misfire detection is delayed until ECT is more than 21°C (70°F) . If start-up ECT is more than -7°C (20°F) , misfire detection begins after a 5 second delay.
CONDITIONS FOR SETTING THE DTC The VCM detects a deceleration in the crankshaft speed characteristic of either an emission type misfire or a catalyst damaging type misfire.ACTION TAKEN WHEN THE DTC SETS If the VCM determines that the engine misfire is significant enough to have a negative impact on emissions, the VCM turns ON the Malfunction Indicator Lamp (MIL) after the misfire has been detected on 2 non-consecutive trips under the same operating conditions. If the misfire is severe enough that catalytic converter damage could result, the MIL flashes while the misfire is present.CONDITIONS FOR CLEARING THE MIL OR DTC
DIAGNOSTIC AIDS The Misfire Index counts the number of misfires. The scan tool can monitor the Misfire Index. There is a current and history misfire counter for each cylinder. Use the current misfire counter in order to determine which cylinder is misfiring or use the history misfire counter for misfires that are not currently present. Many different condition could cause an intermittent misfire.Check for the following conditions:
An intermittent may be caused by any of the following conditions:
Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent and Poor Connections in Diagrams.If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Diagrams.
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