Owner's Problem Description
The owner reports intermittent issues with the tachometer not working after a friend replaced the ignition coil. The car sometimes cuts off while driving and exhibits a misfire. The owner is unsure if replacing the distributor requires flashing the computer. The check engine light has been intermittently on, indicating potential misfire codes. The vehicle was previously operating fine until recent repairs.
Professional Technical Analysis
The 1997 Chrysler Cirrus, equipped with a 2.5L engine and approximately 150,000 miles, is experiencing a combination of issues primarily linked to the ignition system. The tachometer intermittently fails to function, which often points to a signal disruption from the ignition control module or faulty connections at the distributor cap. The vehicle has exhibited stalling behaviors while in motion, alongside noticeable misfire occurrences. The check engine light has illuminated sporadically, suggesting underlying misfire codes, potentially P0300 (Random/Multiple Cylinder Misfire Detected) or P0301-P0304 (specific cylinder misfires). Given the vehicle's age and mileage, it is plausible that the ignition components, including the distributor and coil, have suffered wear and may contribute to these symptoms. Additionally, the broken connection at the distributor cap where the prong fits indicates a need for thorough inspection of the ignition system wiring and components. Intermittent electrical issues could also stem from corroded connections or damaged wiring harnesses, particularly in high-vibration areas. An assessment of the ignition coil's resistance (should be between 0.7-1.5 ohms for primary winding) and the distributor's signal output is critical in diagnosing the root cause. The vehicle's current operational condition poses safety concerns, given the possibility of stalling in traffic, which warrants immediate attention.
Possible Causes
Most common causes (ordered by frequency):
- Distributor Cap Connection Failure: The connection where the prong fits into the distributor cap is broken, leading to poor electrical contact. This can cause intermittent ignition failures, affecting engine operation and resulting in stalling and misfires. Inspect the distributor for internal damage as well as the integrity of the cap and rotor. Replacement of the cap (OEM P/N 4693756) is recommended if any cracks or signs of wear are evident. - Intermittent tachometer failure, stalling while driving, check engine light occasionally illuminated with misfire codes.
- Ignition Coil Fault: The ignition coil may not be providing sufficient voltage to the distributor, particularly if it was recently replaced. Resistance should be within 0.7-1.5 ohms for the primary circuit. Testing the coil under load with a multimeter can reveal if it is failing to deliver the necessary spark energy. - Intermittent misfire during acceleration, difficulty starting, potential stored codes related to ignition system faults.
- Faulty Wiring or Connectors: Damaged or corroded wiring leading to the ignition system can interrupt signals and power delivery, causing stalling and misfires. Inspect all wiring harnesses and connectors associated with the ignition system for signs of wear or corrosion. Use a multimeter to check for continuity and proper voltage at connections. - Check engine light on with intermittent operation of ignition system, evidence of corrosion on connectors.
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 full scan using a professional OBD-II scanner or GeekOBD APP to retrieve any stored trouble codes. Focus on misfire-related codes (P0300-P0304) and document freeze frame data for the conditions when the vehicle exhibited symptoms. Assess the status of the check engine light and any pending codes.
- STEP 2 - Visual Inspection of Ignition Components: Conduct a thorough visual check of the ignition coil, distributor cap, and wiring. Look for signs of wear, corrosion, or damage. Pay particular attention to the connections at the distributor cap and ensure they are secure. If any components appear compromised, recommend replacement with OEM parts.
- STEP 3 - Component Testing: Using a multimeter, check the resistance of the ignition coil to confirm it falls within the 0.7-1.5 ohms range. Test the voltage output from the coil to the distributor. Additionally, check for continuity in the wiring harnesses leading to the ignition system, ensuring no breaks or shorts are present.
- STEP 4 - Road Test and Live Data Monitoring: Perform a controlled road test while monitoring live data using the GeekOBD APP. Observe any changes in ignition timing, fuel trims, and RPM fluctuations. Document any incidents of stalling or misfires during the drive, as this data will be essential for pinpointing the issue.
