2000 Mazda B2500 SX, AutomaticFACTORY OEM SERVICE PROCEDURE

Diagnostic Index: Backfires

DETECTION CONDITION AND POSSIBLE CAUSE

8 BACKFIRES
DESCRIPTION 
  • Sound produced from exhaust system
BACKFIRES INSPECTION

STEP INSPECTION ACTION
1 PRELIMINARY CHECKS
  • Perform the following preliminary checks:
  • Vacuum lines (check for damage and proper routing).
  • Spark plug wire routing (proper firing order).
  • Are all checks OK? 
 Yes Go to step 2.
No Service as required. Verify symptom no longer exists.
2 PERFORM PCM QUICK TEST
  • Are any DTCs displayed during Continuous Memory, Key ON, Engine OFF (KOEO) or Key ON, Engine Running (KOER) Self Tests?
 Yes Check for cause.

See DIAGNOSTIC TROUBLE CODE NUMBERS .
No Go to step 3.
3 CHECK SECONDARY IGNITION SYSTEM
  • Is strong blue spark visible at each disconnected high-tension lead while cranking engine? 
 Yes Check spark plugs.
If OK, go to step 4. If not OK, clean or replace spark plugs.
No Go to step 4.
4 CHECK FUEL DELIVERY SYSTEM Yes Go to step 5.
No If pressure is greater than 496 kPa (72 psi), 3.0L Flex Fuel 517 kPa (75 psi): Replace fuel pump module.

See FUEL PUMP in REMOVAL, OVERHAUL, AND INSTALLATION article in Engine Performance .


If pressure is less than 386 kPa (56 psi), 3.0L Flex Fuel 380 kPa (55 psi): Check fuel supply line for restriction.
5 CHECK FUEL DELIVERY SYSTEM Yes Check injector for leakage.

See TEST 12: FUEL INJECTOR INSPECTION .


If injector leaks, service as necessary.

See FUEL RAILS & INJECTORS in REMOVAL, OVERHAUL, AND INSTALLATION article in Engine Performance .


If injector OK, go to step 6.
No Check fuel supply line for restriction.
6 CHECK BASE ENGINE
  • Check for base engine concerns (such as improper compression, worn camshaft/valve train, gasket leaks).

    See ENGINE COMPONENT TESTS .

  • Is a fault indicated? 
 Yes Service as required.
No Go to step 7.
7 CHECK EXHAUST SYSTEM
  • Is there a restriction in the exhaust system? 
 Yes Service as required.
No Go to step 8.
8
  • Verify test results. If OK,

See DIAGNOSTIC INDEX  to service any additional symptoms
Factory Service Tools

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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.