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2018 Pacifica Rough Idle, Stalling, and ESS Not Engaging

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Robert C. · rep 0 · May 22, 5:50 AM · 1 replies · solved · Question

Vehicle: 2018 Chrysler Pacifica Touring L

Hey everyone,

I'm having some frustrating issues with my 2018 Chrysler Pacifica Touring L. Lately, it's developed a really rough idle, especially when I'm stopped at a light. Sometimes it feels like it's going to stall, and it actually has a couple of times when pulling away from a stop.

On top of that, the Engine Stop-Start (ESS) system hasn't been working at all. It used to engage regularly, but now the light on the dash just says "ESS OFF" or it simply doesn't activate, even when all conditions seem right (engine warm, battery charged, etc.).

I haven't seen a check engine light yet, but the rough idle is definitely concerning. Has anyone experienced similar problems with their Pacifica? Any ideas on what could be causing this or what I should check first? Thanks in advance for any help!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:50 AM

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ClearTheCode admin answer:

It sounds like your 2018 Chrysler Pacifica is experiencing a combination of issues that could be related to engine performance and the ESS system. Here's a breakdown of potential causes and steps:

  1. Rough Idle/Stalling:

    • Causes: A rough idle and stalling often point to issues with the engine's air, fuel, or ignition systems. Common culprits include:
      • Ignition System: Worn spark plugs, faulty ignition coils, or bad spark plug wires.
      • Fuel System: Clogged fuel injectors, a failing fuel pump, or a dirty fuel filter.
      • Air System: A dirty or failing Mass Air Flow (MAF) sensor, a clogged air filter, or a vacuum leak.
      • PCV Valve: A stuck or clogged PCV (Positive Crankcase Ventilation) valve can cause vacuum issues and rough idle.
      • Throttle Body: A dirty throttle body can restrict airflow and lead to poor idle quality.
    • Diagnostics: Even without a Check Engine Light, a pending code might be present. Common codes for these symptoms include P030x (misfire on cylinder x), P0171/P0174 (lean condition), or P0507 (idle air control system RPM higher than expected).

  2. ESS Not Engaging:

    • The ESS system is designed with many interlocks and will not engage if certain conditions aren't met.
    • Causes:
      • Battery Health: The most common reason for ESS not engaging is a weak or aging auxiliary battery (or main battery). The system requires a strong charge to operate.
      • Temperature: Extreme ambient or engine temperatures can prevent ESS activation.
      • HVAC Demand: High demand from the HVAC system (e.g., max A/C or defrost) can disable ESS.
      • Brake Pedal Pressure: Insufficient brake pedal pressure.
      • Hood/Door Ajar: Safety interlocks.
      • Engine Performance Issues: If the engine itself is running poorly (like your rough idle), the ESS system will disable itself to prevent further issues.

  3. When to See a Shop:

    • Given the combination of rough idle, stalling, and ESS malfunction, it's highly recommended to have your Pacifica professionally diagnosed. A qualified technician can:
      • Perform a comprehensive scan for active and pending diagnostic trouble codes (DTCs).
      • Test the main and auxiliary batteries.
      • Inspect the ignition system (plugs, coils).
      • Check for vacuum leaks and inspect the PCV valve.
      • Clean the throttle body and MAF sensor.
      • Evaluate fuel pressure and injector performance.

Addressing the underlying engine performance issue will likely resolve the ESS problem as well, as the system relies on optimal engine operation.

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