engine MAZDA MX-5 1994 Workshop Manual

TROUBLESHOOTING GUIDE 5 ENGINE STALLS AT IDLE - BEFORE WARM-UP IESCRIPTION I Engine starts normally but vibrates excessively and stalls at idle before warm-up TROUBLESHOOTING HINTS] D Low intake air amount Q) AirIFuel mixture too lean Idle speed control malfunction Air leakage of intake air system Air cleaner element clogged Q Poor atomization of fuel Low RVP (summer) fuel used in cold weather Check if "00" is displayed on Self-Diagnosis Check- ar with ignition switch ON page F-79 SELECT SW * SYSTEM SELECT 1 Check switches for correct operation with Self- Diagnosis Checker Monitor Lamp and ignition switch ON SELECT SW A t~= page F-95 -A SYSTEM SELECT 1 MONITOR :heck if PCME terminal voltages are OK :2D, 20 and 2Q) @T page F-146 :heck for correct intake manifold vacuum at idle Vacuum: More than 450 mmHg (17.7 inHg} VACUUM GAUGE - Yes - No Yes - No Yes - No Yes ACTION I 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 w page F-145 Specification: Battery positive voltage (ignition switch ON) Q If OK, replace PCME page F-143 4 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) w 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 for cause (Refer to "Check Point for Each Termi- nal") t@ page F-148 Go to next step Check for air leakage of intake air system components page F-95 Gartner Banana

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 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

TROUBLESHOOTING GUIDE DESCRIPTION I Engine intermittently stops running Before stallina, ennine condition OK 21 [TRO~ESHOOTING HINTS] O Intermittently no spark or no fuel injection Poor connection in wiring harness ENGINE STALLS SUDDENLY (INTERMITTENT) INSPECTION Check if "00" is displayed on Self-Diagnosis Check- er with ignition switch ON page F-79 Tap, move, and wiggle harness and connectors to check if PCME terminal voltages are OK (1 B, 2A, 2B and 2C) @ page F-146 ACTION Go to next step Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) @S page F-81 When checking wiring harness and connectors, tap, move, and wiggle suspect sensor and/or harness to recre- ate problem "88" flashes Check PCME terminal 1 E voltage @S page F-145 Specification: Battery positive voltage (Ignition switch ON) 0 If OK, replace PCME page F-143 0 If not OK, check wiring between PCME and Self-Diagno- sis Checker IS= page F-7 Go to Troubleshooting No.2 "CRANKS NORMALLY BUT WILL NOT START (NO COM- BUSTION)" page F-17 Check for cause (Refer to "Check Point for Each Termi- nal") page F-148 Gartner Banana

TROUBLESHOOTING GUIDE PROUBLESHOOTING HINTS] 3 Air/Fuel mixture too lean or too rich Fuel injection control malfunction Air leakage of intake air system 23 Fuel line pressure low Fuel evaporative malfunction 0 Spark advance control malfunction -- SURGES WHILE CRUISING - STEP DESCRIPTION ( Unexpected change in engine speed which is usually repetitive INSPECTION ACTION - Yes - No - Yes - No Check if "00" is displayed on Self-Diagnosis check- er with ignition switch ON page F-79 Go to next step SELECTSW A SYSTEM SELECT 1 Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) page ~-81 -- - "88" flashes Check PCME terminal 1 E voltage @i= page F-145 Specification: Battery positive voltage (Ignition switch ON) 0 If OK, replace PCME @ page F-143 o If not OK, check wiring between PCME and Self-Diagno- sis Checker US page F-7 Check switches for correct operation with Self- Diagnosis Checker Monitor Lamp and ignition Go to next step switch ON w page F-95 SELECT SW A 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 Disconnect heated oxygen sensor connector and check if condition improves Yes No - Yes Check heated oxygen sensor page F-156 Go to next step :heck if PCME terminal voltages are OK (1 R, 1 T, 2M, 20, and 2Q) as page F-146 Go to next step Check for cause (Refer to "Check Point for Each Termi- nal") * page F-148 Gartner Banana