Mechanical Inspection: Compression

Check engine mechanical condition with a compression gauge, vacuum gauge, or an engine analyzer. See engine analyzer manual for specific instructions.
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)

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 ).