Owner's Problem Description
The owner's 1999 Chrysler Concorde starts without issues but stalls after about 20 minutes of driving. Symptoms include jerking movements before cutting off. After stalling, the vehicle won't restart immediately but can start again after sitting for approximately an hour. The check engine light remains off throughout these issues. Recently, the timing belt was replaced, which may be related.
Professional Technical Analysis
The 1999 Chrysler Concorde, equipped with a 3.5L V6 engine and approximately 127,230 miles, is experiencing intermittent stalling issues characterized by a loss of power after about 20 minutes of operation. The vehicle starts well but exhibits jerking motions before shutting down, indicating potential fuel delivery or ignition system failures. The absence of a check engine light complicates the diagnosis, as monitoring systems are not registering any faults. Given the recent replacement of the timing belt, it's critical to ensure correct timing alignment and tension, as improper installation can lead to performance issues. Furthermore, a systematic approach to diagnosing fuel pressure and ignition quality is warranted. Fuel pressure should be checked for stability, ideally maintaining 35-45 PSI during operation, while spark quality must be verified through inspection of the ignition coil and plug wires. Since the vehicle is able to restart after sitting, it suggests a possible thermal failure of components, such as the ignition control module or fuel pump, often leading to symptoms that worsen with heat-related expansion. The connection integrity of electrical components should also be examined, particularly any related to the fuel pump relay and PCM, which may be influenced by thermal effects. Current vehicle condition indicates a potential safety risk, as stalling in traffic can lead to dangerous situations. A thorough diagnostic check is necessary to address these concerns.
Possible Causes
Most common causes (ordered by frequency):
- Fuel Pump Failure: The fuel pump may be experiencing thermal failure, causing it to stop delivering fuel when hot. When the vehicle is allowed to sit, the pump cools down and resumes operation temporarily. Fuel pressure should be tested at the fuel rail with expected values of 35-45 PSI while running. - Intermittent stalling after extended use, inability to restart until cooled down, fluctuating fuel pressure readings.
- Ignition Control Module (ICM) Issue: The ICM may fail when hot, disrupting ignition timing. This is common in vehicles with aging components and can lead to stalling. Testing the ICM for proper operation at both ambient and elevated temperatures is essential. - Check engine light remains off, stalling occurs primarily after the engine heats up, potential stored codes related to ignition timing.
- Timing Belt Installation Error: Improper installation of the timing belt during replacement can lead to misalignment of timing marks, causing poor engine performance and stalling. Verifying timing alignment after the recent replacement is crucial. - Recent timing belt replacement, symptoms of performance issues immediately following installation.
- Electrical Connection Issues: Poor connections or corroded terminals can lead to intermittent failures in both fuel and ignition systems. Thorough inspection of wiring harnesses and connectors related to the fuel pump and ignition system is recommended. - Fluctuating electrical performance during operation, signs of corrosion on connectors, intermittent operation of vehicle systems.
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 Diagnostic Scan: Begin with a scan using a professional OBD-II scanner or GeekOBD APP to check for any stored codes, even if the check engine light is off. Freeze frame data may provide vital clues about conditions when the stalling occurs.
- STEP 2 - Fuel Pressure Testing: Utilize a fuel pressure gauge to measure fuel pressure at the fuel rail. Pressure should be maintained between 35-45 PSI during operation. If pressure drops significantly, the fuel pump may require replacement.
- STEP 3 - Ignition System Check: Inspect the ignition control module and related components for heat-related failures. Test the ICM at both ambient and elevated temperatures to determine if it’s functioning properly.
- STEP 4 - Timing Belt Verification: Confirm that the timing belt is properly aligned and tensioned according to manufacturer specifications. This can be crucial in preventing stalling and performance issues.
