Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Diagnostic Routines: Notes
These routines list the components and systems that may contribute to a particular driveability condition. They are listed in the order of probability and ease of accomplishment. These routines should be used as check lists and references. These routines may direct you to the QUICK TEST procedures, which will access diagnostic codes and refer you to CIRCUIT TESTS.
The following is a summary of the DIAGNOSTIC ROUTINES found in the DIAGNOSTIC ROUTINE CHARTS .
- Backfires (Induction or Exhaust)
- Diesels (Run-On)
- Lacks Power
- Spark Knock or Ping
- Stalls or Quits
- Stumbles or Hesitates On Acceleration
- Misses or Surges
- Idles Too Fast or Slow Return To Idle
- Idles Rough
- Engine Speeds Up
- Cranks Normally But Won't Start
- Cranks Normally But Slow To Start
- Poor Fuel Economy
- Overheating
- Exhaust Odor or Smoke
- Excessive Oil Use
- Fuel Odor or Leaks
- Fails Emission Test
- Unusual Noises
- "Check Engine" Light Always or Never On
Use the Manual With the Right Hardware
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When to See a Mechanic
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.
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