1994 MAZDA MX-5 Workshop Manual

TROUBLESHOOTING GUIDE ACTION So to next step -- INSPECTION - Yes Check if air cleaner element is clean page F-76 Replace air cleaner element page F-99 No Yes - No - Yes - No Disconnect idle air control valve connector when engine is cold and note idle speed Check if engine speed decreases after warm-up Go to next step Check idle air control valve W page F-106 IAC VALYE CONNECTOR Try known good PCME and check if condition im- Replace PCME W page F-143 35UOFX-023 proves - US page F-144 17 ENGINE STALLS AT IDLE - AFTER WARM-UP SCRIPTI ION I Engine runs normally at idle during warm-up but becomes rough and stalls after warm-up TROUBLESHOOTING HINTS] D AirlFuel mixture too lean 0 Low intake air amount 0 Air lcakaae of intake air system Idle speed control malfunction - INSPECTION I ACTION Repair or replace page F-99 ;heck if air is leaked from intake air system com- )orient as page F-100 Yes Go to next step 3isconnect ldle air control valve connector at idle and check if engine condition is cahnged Yes - No Go to next step IAC VALVE CONNECTOR Check idle air control valve page F-106 30 to troubksho%ng No.10 "LOW IDLE SPEED1 ?OUGH IDLE-AFTER WARM-UP" Gartner Banana

TROUBLESHOOTING GUIDE F 18 ENGINE STALLS DURING START-UP DESCRIPTKlN I Engine unexpectedly stops running while starting VROUBLESHOOTING HINTS] @ Misfire occurs when depressing accelerator Q Lack of engine torque for start-up AirIFuel mixture too rich or too lean AirIFuel mixture too rich or too lean Incorrect ignition timing Weak ignition INSPECTION Check if brakes are dragging Section P Check if "00 is displayed on Self-Diagnosis Check- er with ignition switch ON * page F-79 SELECT SW A Check switches for correct operation with Self- Diagnosis Checker Monitor Lamp and ignition switch ON @ page F-95 Disconnect heated oxygen sensor connector and :heck if condition improves SENSOR CONNECTOR -3 I I - Yes - No Yes Yes No - Yes Low intake air amount Low en~ine com~ression ACTION Repair us Section P Go to next step 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 us page F-145 Specification : Battery positive voltage (Ignition switch ON) If OK, replace PCME rc+r page F-143 6 If not OK, check wiring between PCME and Self-Diagno- sis Checker e page F-7 Go to next step Lamp not ONIOFF with specified switch Check for cause (Refer to specified check sequence) uw page F-96 Lamp always ON Check wiring between PCME terminal 1 D and Self-Diag- nosis Checker page F-7 Check heated oxygen sensor @s page F-156 Go to next step Gartner Banana

TROUBLESHOOTING GUIDE INSPECTION ACTION ;heck if PCME terminal voltages are OK 2M, 20 and 20) usf page F-146 Yes - No Go to next step Check for cause (Refer to "Check Point for Each Terrni- nal") G+F page F-139 >heck if throttle linkage is correctly installed and )perates freely Yes Go to next step Correct, clean, or replace as required any binding or dam- aged linkage and adjust cable deflection at throttle body * page F-101 No - Yes >heck for correct intake manifold vacuum at idle lacuum: More than 450 mmHg (17.7 inHg} VACUUM GAUGE / - - Go to next step Check for air leakage of intake air system components G+F page F-110 >heck if air cleaner element is clean page F-76 Yes Go to next step Replace air cleaner element * page F-99 >heck for correct ignition timing at idle usf page F-76 Yes Check if ignition timing advances when accelerating 0 If advances, go to next step e If no advance, replace PCME page F-143 gnition timing: 10" 2 lo BTDC No - Yes Adjust usf page F-76 >heck for correct fuel line pressure at idle page F-110 Check if fuel line pressure decreases when accelerating quickly %el line pressure: 265-314 kPa {2.7-3.2 kgf/cm2, 38-46 psi) (Vacuum hose to pressure regulator discon- nected) If decreases, check fuel pump maximum pressure page F-115 o If OK, check fuel line and filter for clogging Low pressure Check fuel line pressure while pinching fuel return hose 9 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 Paae F-115 High pressure Check if fuel return line is clogged INSTALL CLAPS o If OK, replace pressure regulator page F-119 o If not OK, replace Gartner Banana

TROUBLESHOOTING GUIDE F INSPECTION Check for correct engine compression Section B Engine compression: 1,255-863 kPa {I 2.8-9.0 kgf/cm2, 182-1 28 psiwOO rpm Try known good PCME and check if condition im- Droves ACTION 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 af page F-144 35UOFX-024 Gartner Banana

TROUBLESHOOTING GUIDE 3ESCRIPTION ( Engine unexpectedly stops running while decelerating or after deceleration JROUBLESHOOTING HINTS] Ingine speed drops too much when releasing accelerator D Idle speed control malfunction Q Engine feedback control malfunction D Fuel cut control malfunction @ Idle speed misadjustment 19 INSPECTION :heck if "00" is displayed on Self-Diagnosis Check- 3r with ignition switch ON page F-79 ENGINE STALLS ON DECELERATION >heck switches for correct operation with Self- Diagnosis Checker Monitor Lamp and ignition switch ON page F-95 SELECT SW A MONITOR kt \A SYSTEM SELECT 1 Disconnect heated oxygen sensor connector and :heck if condition improves >heck if PCME terminal voltages are OK [2D, 20,2U, 2V 2Q, 2Y and 22) its page F-146 - Yes - No Yes Yes No - Yes ACTION Go to next step Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) page Fa1 "88" flashes Check PCME terminal 1 E voltage us? page F-145 Specification: Battery positive voltage (Ignition switch ON) 6 If OK, replace PCME 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 ONJOFF 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 Check heated oxygen sensor @Tage F-156 Go to next step Go to next step Check for cause (Refer to "Check Point for Each Termi- nal") E%= page F-148 Gartner Banana

TROUBLESHOOTING GUIDE INSPECTION Disconnect idle air control valve connector at idle and check if engine condition is changed IAC VALVE CONNECTOR . - :heck for correct idle speed page F-77 Idle speed: 850 r 50 rpm (MT) 800 + 50 rpm (AT) GND TEN I CONNECT TERMINAL AIR ADJUSTING SCREW Try known good PCME and check if condition irn- woves Daae F-144 Yes - No - Yes ACTION 30 to next step ;heck idle air control valve page F-106 30 to next step 4djust page M7 Gartner Banana

TROUBLESHOOTING GUIDE DESCRIPTION I : Engine unexpectedly stops running at idle when AIC, PIS, or EIL ON AX, PIS, headlight, blower fan and electric coolant fan OK 20 [TROUBLESHOOTING HINTS] O ldle speed control malfunction No input signal from switch ldle speed misadjustment ldle air control valve stuck ENGINE STALLS AT IDLE - WHEN AIC, PIS, OR EIL ON INSPECTION Check if "00" is displayed on Self-Diagnosis Check- er with ignition switch ON * page F-79 SELECT SW A SYSTEM SELECT 1 Check switches for correct operation with Self- Diagnosis Checker Monitor Lamp and ignition switch ON tw page F-95 SELECT SW A Check if PCME terminal voltages are OK (IG, 1 P, 1 U, 2D,2Q and 2W) page F-146 Check for correct idle speed page F-77 ldle speed: 850 2 50 rpm (MT) 800 2 50 rpm (AT) GND TEN 1 AIR ADJUSTING SCREW CONNECT TERMINAL - Yes - No Yes - No Yes - No Yes - No Go to next step ACTION 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) 0 If OK, replace PCME page F-143 s 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) page F-96 Lamp always ON Check wiring between PCME terminal 1 D and Self-Diag- nosis Checker IS page F-7 Go to next step Check for cause (Refer to "Check Point for Each Termi- nal") page F-148 Go to next step Adjust page F-77 Gartner Banana

TROUBLESHOOTING GUIDE INSPECTION Disconnect idle air control valve connector at idle and check if engine condition is changed IAC VALVE CONNECTOR Try known good PCME and check if condition im- proves Daae F-144 - Yes ACTION Go to next step Check idle air control valve page F-106 Gartner Banana