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HOMESERVICE MANUALSMAZDA1991MX-6 GT, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROLS - BASIC TESTINGPRELIMINARY INSPECTION & ADJUSTMENTSMECHANICAL INSPECTIONCOMPRESSION
1991 Mazda MX-6 GT, Standard

Mechanical Inspection: Compression

1991 Mazda MX-6 GT, StandardSECTION Compression
  1. Check engine mechanical condition with a compression gauge, vacuum gauge, or an engine analyzer. See engine analyzer manual for specific instructions.
  2. On RX7 models, connect Compression Tester (49F0189A0) to front rotor housing and battery. Fully depress accelerator pedal and crank engine for 5-10 seconds. Note compression of 3 front combustion chambers and engine cranking speed. See COMPRESSION SPECIFICATIONS TABLE. Use same procedure to check rear chambers.
WARNING: DO NOT use ignition switch during compression tests on fuel injected vehicles. Use a remote starter to crank engine. Fuel injectors on many models are triggered by ignition switch during cranking mode, which can create a fire hazard or contaminate the engine's oiling system.
COMPRESSION SPECIFICATIONS

Application Minimum psi (kg/cm2 ) @ RPM Standard psi (kg/cm2 ) @ RPM
B2200 121 (8.5)@300 173 (12.2)@300
B2600i 142 (10.0)@280 185 (13.0)@280
Miata & 323 (1) 135 (9.5)@300 192 (13.5)@300
MPV
2.6L 142 (10.0)@280 185 (13.0)@280
3.0L 121 (8.5)@300 164 (11.5)@300
MX-6 & 626
Non-Turbo 114 (8.0)@265 162 (11.4)@265
Turbo 98 (6.9)@265 139 (9.8)@265
Navajo (2) 100 (7.0) (2) 100 (7.0)
Protege
SOHC (1) 121 (8.5)@300 173 (12.2)@300
DOHC (1) 128 (9.0)@300 182 (12.8)@300
RX7 (3) 43 (3.0)@250 85 (6.0)@250
929
SOHC 114 (8.0)@300 164 (11.5)@300
DOHC 125 (8.8)@300 179 (12.6)@300
(1) Difference between cylinders should not be more than 28 psi (2.0 kg/cm2 ).
(2) Lowest compression reading should not be less than 75 percent of highest compression reading.
(3) Difference between chambers should not be more than 21 psi (1.5 kg/cm2 ).
RENDER: 1.0x

NO RELATED

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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.