Owner's Problem Description
The owner reports that their 2000 Dodge Dakota with a 4.7L engine and 192,000 km suddenly started running very roughly after a quick stop. They managed to drive it home by using the gas and brake. An OBD-II scan revealed a P0202 code indicating an injector circuit issue for cylinder 2, prompting an injector replacement, which did not resolve the issue. The vehicle still runs rough and stalls intermittently. Previous checks confirmed that the injectors are functioning properly.
Professional Technical Analysis
The 2000 Dodge Dakota in question features a 4.7L V8 engine coupled with an automatic transmission, accumulating approximately 192,000 km. The owner reports a sudden onset of rough running and stalling, occurring shortly after exiting the vehicle for a brief period. Initial diagnostics revealed a P0202 fault code, indicating an open circuit or failure in the injector circuit for cylinder 2. Despite replacing the injector, the issue persists, suggesting the problem may lie elsewhere. The vehicle's symptoms of running rough and stalling can be attributed to several factors including fuel delivery issues, electrical faults, or vacuum leaks. Given the nature of the reported symptoms, it is critical to assess the fuel pump pressure, which should be within the range of 55-65 PSI for optimal performance. Additionally, checking for vacuum leaks around intake manifold gaskets and vacuum hoses is imperative. The fact that the code keeps returning after clearing indicates a persistent issue potentially involving the PCM (Powertrain Control Module) or wiring harness leading to the injector. Current testing should include verifying power to the injector using a noid light to ensure proper signal and voltage are present during operation. A thorough inspection of the engine speed sensor should also be conducted since its failure can cause stalling and rough running. The vehicle's current condition is concerning due to these intermittent stalling issues, which pose significant safety risks.
Possible Causes
Most common causes (ordered by frequency):
- Injector Circuit Issue: The P0202 code indicates a problem with the injector circuit for cylinder 2, which could be due to a faulty wiring harness, poor connections, or the injector itself failing. Testing should include checking the injector harness for continuity and resistance (should be around 12-15 ohms), and using a noid light to confirm proper pulse width from the PCM when the engine is running. - Persistent P0202 code after injector replacement, evidence of wiring issues or poor connections.
- Fuel Pressure Insufficiency: If the fuel pump is not delivering adequate pressure (should be 55-65 PSI), it can cause poor fuel atomization leading to rough running and stalling. Fuel pump pressure should be tested at the fuel rail service port using a fuel pressure gauge. Any significant drop in pressure could indicate a failing pump or clogged fuel filter. - Inconsistent engine performance, potential signs of fuel starvation.
- Vacuum Leak: A vacuum leak in the intake system can lead to an incorrect air-fuel mixture, resulting in rough running. Check all vacuum hoses and gaskets, particularly around the intake manifold, for signs of wear or disconnection. A smoke test may be helpful in identifying any hidden leaks. - Rough idle, hissing noises during operation indicating a potential leak.
- PCM Failure: While less common, a malfunctioning PCM could lead to improper fuel delivery or injector control issues, contributing to the stalling and rough running. If other tests fail to identify the issue, further diagnostics may be necessary to evaluate the PCM's functionality. - Intermittent issues not resolved by replacing injectors or checking wiring.
Diagnostic Steps
Professional Diagnosis Process
Follow these systematic steps to accurately diagnose the issue. Each step builds on the previous one to ensure accurate diagnosis.
- STEP 1 - OBD-II Code Retrieval: Start by using a professional OBD-II scanner or the GeekOBD APP to retrieve and analyze any stored diagnostic trouble codes (DTCs). Focus on the P0202 code and examine related freeze frame data to understand the conditions under which it occurred. This initial step is crucial in identifying the root cause of the problem.
- STEP 2 - Injector Functionality Testing: Verify the functionality of the injector circuit for cylinder 2 using a noid light to check for proper pulsing during cranking. Measure the injector resistance to ensure it is within the specification (12-15 ohms). Document any irregularities observed during testing.
- STEP 3 - Fuel Pressure Testing: Connect a fuel pressure gauge to the fuel rail service port to measure the fuel pump pressure. It should maintain a steady pressure between 55-65 PSI under cranking conditions. If the pressure is inadequate, further investigate the fuel pump and filter for potential issues.
- STEP 4 - Vacuum Leak Inspection: Conduct a thorough inspection of all vacuum hoses and gaskets for signs of wear or damage. A smoke test can be employed to identify any hidden leaks in the intake system. Document any findings and address leaks as necessary.
