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HOMESERVICE MANUALSMAZDA1999626 ES, 2.5 D, STANDARDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 392 (SYMPTOM TROUBLESHOOTING (ENGINE CONTROL SYSTEM) AJ)NO.8 ENGINE RUNS ROUGH/ROLLING IDLENOTES
1999 Mazda 626 ES, 2.5 D, Standard

No.8 Engine Runs Rough/Rolling Idle: Notes

1999 Mazda 626 ES, 2.5 D, StandardSECTION Notes
WARNING: This page is about a different car, the 2005 Mazda MPV. However, it is still accessible from the selected car via links, so may be relevant.
ENGINE RUNS ROUGH/ROLLING IDLE - DESCRIPTION AND POSSIBLE CAUSE

8 Engine runs rough/rolling idle
DESCRIPTION 
  • Engine speed fluctuates between specified idle speed and lower speed and engine shakes excessively.
  • Idle speed is too slow and engine shakes excessively.
POSSIBLE CAUSE 
  • Air leakage from intake-air system parts
  • A/C system improper operation
  • Erratic signal to ignition coil
  • Purge solenoid valve malfunction
  • IAC valve improper operation
  • EGR valve malfunction
  • Erratic or no signal from CMP sensor
  • Low engine compression
  • Erratic signal from CKP sensor
  • Poor fuel quality
  • PCV valve malfunction
  • Air cleaner restriction
  • Restriction in exhaust system
  • Disconnected electrical connectors
  • Inadequate fuel pressure
  • Fuel pump mechanical malfunction
  • Fuel leakage from fuel injector
  • Fuel injector clogging
  • Engine overheating
  • Vacuum leakage
    WARNING:
    • The following troubleshooting flow chart contains the fuel system diagnosis and repair procedures. Read the following warnings before performing the fuel system services:
      • Fuel vapor is hazardous. It can easily ignite, causing serious injury and damage. Always keep sparks and flames away from fuel.
      • Fuel line spills and leakage are dangerous. Fuel can ignite and cause serious injuries or death and damage. Fuel can also irritate skin and eyes. To prevent this, always complete "BEFORE REPAIR PROCEDURE" and "AFTER REPAIR PROCEDURE" described in this manual.

        (See BEFORE REPAIR PROCEDURE .) (See AFTER REPAIR PROCEDURE )
RENDER: 1.0x

NO RELATED

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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.