1994 MAZDA MX-5 check engine

TROUBLESHOOTING GUIDE 9 LOW IDLE SPEEDIROUGH IDLE - BEFORE WARM-UP IESCRIPTION I Engine speed low or engine vibrates excessively at idle during warm-up TROUBLESHOOTING HINTS] D Low intake air amount Mass airflow sensor stuck Air cleaner element clogged Idle s~eed control Q Low fuel injection amount Fuel injection control malfunction (Correction for coolant temperature) O Poor atomization of fuel Air valve [Correction for coolant temperature ] iTEP I Low RVP (summer) fuel used in cold weather INSPECTION ACTION - Yes Check if "00" is displayed on Self-Diagnosis Check- er with ignition switch ON page F-79 GOG next step Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) trs page F-81 - - "88"flashes Check PCME terminal 1 E voltage page F-145 Specification: Battery positive voltage (Ignition switch ON) 0 If OK, replace PCME @ page F-143 e If not OK, check wiring between PCME and Self-Diagno- sis Checker page F-7 Check switches for correct operation with Self- Diagnosis Checker Monitor Lamp and ignition switch ON ~8 page F-95 SELECT SW A Yes Go to next step Check if PCME terminal voltaaes are OK No - Yes - No - Yes Lamp not ON/OFF with specified switch Check for cause (Refer to specified check sequence) page F-96 Lamp always ON Check wiring between PCME terminal 1 D and Self-Diag- nosis Checker page F-7 Go to next step " (2D, 20 and 2Q) page F-146 Check for cause (Refer to "Check Point for Each Termi- nal") page F-148 Go to next step Check for correct intake manifold vacuum at idle Vacuum: More than 450 mmHg {I?.? inHg) Check for air leakage of intake air system components @ page F-100 INSTALL CLAPS Gartner Banana

F TROUBLESHOOTING GUIDE STEP 5 INSPECTION Check if air cleaner element is clean page F-76 Connect System Selector to data link connector and set Test Switch to "SELF TEST" when engine is cold Check if engine speed decreases as engine warms UD -r tw page F-101 , GND TEN With condition of Step 5 check for correct ignition timing at idle after warm-up G-X page F-76 Ignition timing: 10" + 1" BTDC Try known good PCME and check if condition im- 3roves @S page F-144 - Yes Yes - No - Yes Yes ACTION Go to next step Replace air cleaner element tw page F-99 Go to next step Check air valve @ page F-105 Go to next step Adjust @ page F-76 Replace PCME page F-143 Change fuelto another brand Gartner Banana

TROUBLESHOOTING GUIDE lo 1 LOW IDLE SPEEDIROUGH IDLE - AFTER WARM-UP 3ESCRIPTION I Engine runs normally at idle during warm-up but vibrates excessively after warm-up ;TROUBLESHOOTING HINTS] I> Idle speed control malfunction b AirlFuel mixture too lean Air leakage of intake air system Low fuel line pressure INSPECTION Check if "00" is displayed on Self-Diagnosis Check- er with ignition switch ON m? page F-79 Check switches for correct operation with Self- Diagnosis Checker Monitor Lamp and ignition switch ON page F-95 SELECT SW A Disconnect idle air control valve connector at idle and check if engine condition is charged IAC VALVE - Yes No - Yes - No Yes O Air/Fuel mixture too rich Fuel injection control malfunction (Correction for coolant temperature) @ Poor ignition spark Q Low engine compression ACTION Go to next step Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) page F-81 "88" flashes Check PCME terminal 1 E voltage page F-145 Specification: Battery positive voltage (Ignition switch ON) 6 If OK, replace PCME page F-143 Q If not OK, check wiring between PCME and Self-Diagno- sis Checker page F-7 Go to next step Lamp not ONIOFF with specified switch Check for cause (Refer to specified check sequence) page F-96 Lamp always ON Check wiring between PCME terminal 1 D and Self-Diag- nosis Checker page F-7 Go to next step Check idle air control valve page F-106 Gartner Banana

F TROUBLESHOOTING GUIDE INSPECTION :heck for correct intake manifold vacuum at idle Vacuum: More than 450 mmHg I17.7 inHg) VACUUM GAUGE :heck if PCME terminal voltages are OK (2D, 20 and 2Q) page F-146 :heck for correct ignition timing at idle @S page F-76 Ignition timing: 10" + 1" BTDC :heck for correct fuel line pressure at idle @S page F-11 0 Fuel line pressure: 265--314 kPa f2.7-3.2 kgf/cm2,38-46 psi} (Vacuum hose to pressure regulator discon- INSTALL CLAPS ' :heck if strong blue spark is visible at each discon- iected high-tension lead while cranking engine - -- :heck for correct engine compression @S Section B Engine compression: 1,255-883 kPa (12.8-9.0 kgf/cm2, 182-128 psi)-300 rpm - Yes Yes Yes No - Yes - No - Yes No - Yes - No - ACTION Go to next step Low vacuum Check for air leakage of intake air system components page F-100 Go to next step Check for cause (Refer to "Check Point for Each Termi- nal") page F148 Check for correct idle speed page F77 Idle speed: 850 -c 50 rpm (Mi) 800 + 50 rpm (AT) e If OK, go to next step o If not OK, adjust idle speed page F-77 Adjust page F-76 Go to next step Low pressure Check fuel line pressure while pinching fuel return hose 0 If fuel line pressure quickly increases, check pressure regulator page F-118 0 If fuel line pressure gradually increases, check for clog- ging between fuel pump and pressure regulator If not clogged, check fuel pump maximum pressure page F-115 Go to next step Check ignition system (Refer to Troubleshooting "Misfire") Section G Go to next step Check engine condition Section B Worn piston, piston rings or cylinder wall Defective cylinder head gasket Distorted cylinder head Improper valve seating Valve sticking in guide Gartner Banana

TROUBLESHOOTING GUIDE INSPECTION >heck if throttle valve is closed throttle position Yes when accelerator released I 11 :heck if "00" is displayed on Self-Diagnosis Check- Yes w with ignition switch ON @? page F-79 HIGH IDLE SPEED - AFTER WARM-UP SELECT SW A SYSTEM SELECT 1 FROUBLESHOOTING HINTS] Excessive intake air supplied to engine O Throttle valve not fully closed @ ldle speed control malfunction Air valve not closing ldle air control valve stuck Incorrect coolant temperature signal STEP 1 >heck switches for correct operation with Self- I Yes liagnosis Checker Monitor Lamp and ignition ;witch ON page F-95 SELECT SW A ACTION Go to next step Check if throttle linkage is correctly installed and operates freely @? page F-103 o If OK, go to next step o If not OK, clean, adjust or replace linkage Daae 6103 Go to next step - Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) @? page F-81 "88" flashes Check PCME terminal 1 E voltage @S page F-145 Specification: Battery positive voltage (Ignition switch ON) 6 If OK, replace PCME E=T page F-143 o If not OK, check wiring between PCME and Self-Diagno- sis Checker @? page F-7 Go to next step Lamp not ONlOFF with specified switch Check for cause (Refer to specified check sequence) E=T page F-96 am^ always ON Check wiring between PCME terminal ID and Self-Diag- IOS~S Checker @? page F-7 Gartner Banana

TROUBLESHOOTING GUIDE INSPECTION Zonnect System Selector to data link connector and set Test Switch to 'SELF TEST" when engine s cold :heck if engine speed decreases as engine warms - T SW. Disconnect idle air control valve connector at idle and check if engine condition is changed IAC VALYE CONNECTOR Pinch PCV hose with pliers and check if engine speed decreases Check if PCME terminal voltages are OK [I R, 2D, 20 and 2Q) page 6146 Yes No - Yes - No - Yes - No - Yes - No ACTION 30 to next step :heck air valve w page -05 30 to next step Check idle air control valve page F-106 Check PCV valve page F-130 30 to next step Try known good PCME page F-144 Check for cause (Refer to "Check Point for Each Termi- ial") page F-148 35UOFX-Oli Gartner Banana

TROUBLESHOOTING GUIDE ldle speed control malfunction Engine speed feedback control malfunction ldle air control valve stuck 12 INSPECTION LOW IDLE SPEED - WHEN AIC, PIS, OR EIL ON Check if "00" is displayed on Self-Diagnosis Check- er with ignition switch ON @? page F-79 SELECT SWA SYSTEM SELECT 1 I Check switches for correct operation with Self- Diagnosis Checker Monitor Lamp and ignition switch ON page F-95 SELECT SW A DESCRIPTIOH MONITOR [LAMP &\L SYSTEM SELECT 1 : Engine speed decreases at idle when NC, PIS, or EIL ON NC, PIS, headlights, blower fan and electric coolant fan operate normally Check if continuity exists between data link con- nector terminal TEN and ground --., rrROUBLESHOOTlNG HINTS] Disconnect idle air control valve connector at idle and check if engine condition is changed IAC VALYE CONNECTOR /' Yes - No Yes Yes No - Yes - No - ACTION Go to next step Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) US= page F-81 "88" flashes Check PCME terminal 1 E voltage * page F-145 Specification: Battery positive voltage (Ignition switch ON) 6 If OK, replace PCME page F-143 G If not OK, check wiring between PCME and Self-Diagno- sis Checker page F-7 Go to next step Lamp not ONIOFF with specified switch Check for cause (Refer to specified check sequence) as page F-96 Lamp always ON Check wiring between PCME terminal I D and Self-Diag- nosis Checker @T page F-7 Check for short circuit in wiring between data link connec- tor terminal TEN and ground as page F-7 Go to next step Try known good PCME page F-144 Check idle air control valve @? page F-106 Gartner Banana

TROUBLESHOOTING GUIDE )ESCRIPTION I Engine starts normally but vibrates excessively just after starting TROUBLESHOOTING HINTS] D Fuel injection control and idle speed control malfunction Q Idle speed misadjustment Start signal not input to PCME O Ignition timing misadjustment a INSPECTION ACTION -- 13 Zheck if "00" is displayed on Self-Diagnosis Check- sr with ignition switch ON page F-79 ROUGH IDLE JUST AFTER STARTING Yes Go to next step Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) page F-81 "88" flashes Check PCME terminal I E voltage page -45 Specification: Battery positive voltage (Ignition switch ON) + If OK, replace PCME page F-143 Q If not OK, check wiring between PCME and Self-Diagno- sis Checker page F-7 Zheck switches for correct operation with Self- Diagnosis Checker Monitor Lamp and ignition switch ON r@= page F-95 SELECT SW A Yes Go to next step MONITOR SYSTEM SELECT 1 Lamp not ONlOFF with specified switch Check for cause (Refer to specified check sequence) page F-96 Lamp always ON Check wiring between PCME terminal 1 D and Self-Diag- nosis Checker page F-7 :heck if PCME terminal 1 C voltage is OK page F-145 Yes Go to next step I Check for cause (Refer to "Check Point for Each Termi- nal") uzf page F-148 Voltage: Approx. 10V (While cranking) 3heck for correct ignition timing at idle @? page F-76 Yes Check for correct idle speed page F-77 I ldle speed: 850 +. 50 rpm (MT) 800 2 50 rpm (AT) gnition timing: 10" + lo BTDC Q If OK, go to next step Q If not OK, adjust idle speed page F-77 Adjust E+F page F-76-1 Try known good PCME and check if condition im- )roves page F-144 Gartner Banana