Owner's Problem Description
The owner reports that while driving at 65 mph on the interstate, the engine dies suddenly without warning. After pulling over, the vehicle will not restart for about 10 minutes, although the starter engages. Additionally, the engine idles erratically, racing up and down. No check engine light has illuminated during these incidents, indicating a potential intermittent issue that may be fuel or spark-related.
Professional Technical Analysis
The 2000 Dodge Dakota, equipped with a 3.9L V6 engine and an automatic transmission, has approximately 120,000 miles on the odometer. The main symptom reported is the engine dying suddenly while driving at highway speeds. Upon stopping, the vehicle is unresponsive to the starter until it cools down for about 10 minutes. Additionally, the engine exhibits erratic idling behavior. This symptom could be indicative of several issues, including a failing ignition control module (ICM), fuel pump malfunction, or sensor failures such as the crankshaft position sensor. The lack of a check engine light further complicates diagnosis, as it suggests that the PCM (Powertrain Control Module) is not detecting any faults. However, intermittent faults can evade detection, especially if they do not trigger a hard fault code. The racing idle suggests potential issues with the throttle position sensor (TPS) or an air intake leak. Given the vehicle's mileage, common failure points can include the fuel pump, which often experiences wear and can lead to inconsistent pressure, or the ICM, which tends to fail under heat due to thermal stress. Careful observation of electrical connections and grounds while the vehicle is running can provide insight into possible intermittent failures. Safety is a priority here; if the vehicle is stalling while driving, the potential for loss of power steering and braking should be considered. The first step should be to check the fuel pressure, which should be around 60-65 PSI, and monitor for any signs of electrical overheating or loose connections.
Possible Causes
Most common causes (ordered by frequency):
- Ignition Control Module (ICM) failure: The ICM in this model can suffer from thermal breakdown, particularly when subjected to high temperatures, potentially causing the engine to stall. This is a known issue for many Dodge vehicles of this era. Symptoms typically include intermittent stalling and difficulty restarting until the module cools down. - Intermittent stalling, difficulty restarting after engine is hot, common failure pattern in similar models.
- Fuel pump failure: A failing fuel pump may not maintain adequate pressure, especially under load, leading to engine stalling. This could be due to wear or electrical issues within the pump. Symptoms include engine dying when driving and difficulty starting. - Inconsistent engine performance, inability to restart until cool, pressure tests indicating low fuel pressure.
- Crankshaft Position Sensor (CKP) failure: This sensor can fail intermittently, leading to loss of spark and engine stalling. When the CKP fails, it may not trigger the ignition system, which would prevent the engine from starting until the sensor cools down. - No spark during cranking, symptoms often match CKP failure patterns, intermittent fault codes possible.
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 - Initial OBD-II Diagnosis: Use a professional OBD-II scanner or GeekOBD APP to scan for any stored or pending fault codes, even if the check engine light is off. This will help identify any intermittent faults that may not have triggered a light. Pay attention to freeze frame data if codes are present.
- STEP 2 - Fuel Pressure Testing: Connect a fuel pressure gauge to the fuel rail and check the fuel pressure while the engine is running. It should maintain a pressure between 60-65 PSI. If the pressure drops significantly during operation, the fuel pump may be failing. Document the results for comparison during future tests.
- STEP 3 - Spark Testing: When the vehicle does not start, check for spark at the spark plugs. Use an extra spark plug connected to the ignition wire to see if there is a spark when cranking. If there is no spark, it may indicate an issue with the ICM or CKP sensor.
- STEP 4 - Visual Inspection: Inspect all electrical connections, grounds, and wiring for signs of corrosion, wear, or damage. Pay special attention to the ICM and CKP sensor wiring. Look for loose connections that could cause intermittent issues. Document findings and repair as necessary.
