fuel MAZDA MX-5 1994 Repair Manual

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 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 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 F b AirIFuel mixture leaning when depressing accelerator Fuel injection control malfunction (Correction for accelerating condition) Air leakage of intake air system Fuel line Pressure low 22 park adbance control malfunction HESITATESISTUMBLES ON ACCELERATION 0 - STEF DESCRIPTION] Flat spot occurs just after accelerator depressed or mild jerking occurs during acceleration rrROUBLESHOOTlNG HINTS] ACTION INSPECTION Check if "00" is displayed on Self-Diagnosis Check- er with ignition switch ON page F-79 SELECT SWA SYSTEM SELECT 1 - Yes Go to next step No - Yes - No Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) uz page F-81 "88'1 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 US page F-7 Check switches for correct operation with Self- Diagnosis Checker Monitor Lamp and ignition switch ON Go to next step page F-95 SELECT SW A 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 Disconnect heated oxygen sensor connector and :heck if condition improves Yes - No - Yes -- -- Check heated oxygen sensor @s page F-156 Go to next step - :heck if PCME terminal voltages are OK :2M, 20, and 2Q) page F-146 Go to next step Check for cause (Refer to "Check Point for Each Termi- nal") page F-148 Gartner Banana

TROUBLESHOOTING GUIDE ACTION Go to next step INSPECTION :heck if throttle linkage is correctly installed and 3perates freely - Yes - No - Yes - No - Yes - No Correct, clean, or replace as required any binding or dam- aged linkage and adjust cable deflection at throttle body @a page F-103 Go to next step :heck if air duct and air hoses are correctly nstalled page F-99 Repair ~8 page F-99 Go to next step ;heck for correct intake manifold vacuum at idle Vacuum: More than 450 mmHg (17.7 inHg) VACUUM GAUGE Check for air leakage of intake air system components page F-100 :heck if air cleaner element is clean ttzr page F-76 Yes - No Go to next step Replace air cleaner element @a page F-99 >heck for correct ignition timing at idle page F-76 Yes - No Check if ignition timing advances when accelerating Q If advances, go to next step Q If no advance, replace PCME page F-143 Adjust page F-76 gnition timing: 10" a lo BTDC ;heck for correct fuel line pressure at idle page F-110 Yes - No - Yes Check if fuel line pressure decreases when accelerating quickly %el line pressure: 265-314 kPa I2.7-3.2 kgf/cm2, 38-46 psi] (Vacuum hose to pressure regulator discon- a If decreases, check fuel line and filter for clogging 0 If no decrease, go to next step Low pressure Check fuel line pressure while pinching fuel return hose If fuel line pressure quickly increases, check pressure regulator @a 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 INSTALL CLAPS ;heck for EGR system malfunction page F-124 Repair or replace Go to next step Repair or replace t@~ page F-128 ;heck if exhaust system is restricted page F-128 Yes Go to next step Try known good PCME and check if condition im- )roves page F-144 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

F TROUBLESHOOTING GUIDE INSPECTION ACTION Check if throttle linkage is correctly installed and operates 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 r@ page F-103 Check for correct intake manifold vacuum at idle Vacuum: More than 450 mmHg I17.7 inHg) VACUUM GAUGE / Yes Go to next step No - Yes Check for air leakage of intake air system components r@ page F-100 Go to next step Check if air cleaner element is clean page F-76 Replace air cleaner element page F-99 Check for correct ignition timing at idle page F-76 Yes - No Check if ignition timing advances when accelerating .I, If advances, go to next step o If no advance, replace PCME page F-143 Adjust r@ page M6 Ignition timing: 10" -r- lo BTDC Check for correct fuel line pressure at idle page F-110 Yes Check if fuel line pressure decreases when accelerating quickly Fuel line pressure: 265-314 kPa (2.7-3.2 kgf/cm2, 38-46 psi) (Vacuum hose to pressure regulator discon- nected) o If decreases, check fuel line and filter for clogging 0 If no decrease, go to next step No - Yes Low pressure Check fuel line pressure while pinching fuel return hose 0 If fuel line pressure quickly increases, check pressure regulator page F-113 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 INSTALL CLAPS Repair or replace Check for EGR system malfunction page F-124 No - Yes - No Go to next step - -- Check if exhaust system is restricted page F-128 -- - Repair or replace So to next step Try known good PCME and check if condition im- 3roves page F-144 Gartner Banana

TROUBLESHOOTING GUIDE F 24 Overloaded ) Low intake air amount Throttle valve not oDen fully LACK OF POWER ESCRIPmH - TEP - 1 - 2 : Performance poor under load Reduced maximum speed :heck factors other than engine Clutch slipping as Section H Brake dragging Section P Low tire pressure as Section Q Unrecommended tire size Section Q ;heck if throttle valve wide open throttles when lepressing accelerator fully rROUBLESHOOTlNG HINTS] Factors other than engine malfunction O AirlFuel mixture too lean or too rich Clutch slipping Fuel line pressure low or high Brake dragging Insufficient fuel injection Low tire pressure @ Poor ignition Unrecommended tire size 8 Low engine compression >heck if "00 is displayed on Self-Diagnosis Check- !r with ignition switch ON page F-79 :heck switches for correct operation with Self- Diagnosis Checker Monitor Lamp and ignition switch ON as page F-95 SELECT SW A YSTEM SELECT 1 - Yes Yes Clogged intake air system - INSPECTION I - C 0 0 0 0 - c C - ( E -- I I i I I No - Yes No - Yes - No ACTION %to next step 20 to next step Sheck if accelerator cable is correctly installed page F-103 3 If OK, check throttle body @r page F-101 3 If not OK, install accelerator cable correctly page F-103 - 30 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 @r page F-145 Specification: Battery positive voltage (Ignition switch ON) o If OK, replace PCME page F-143 O If not OK, check wiring between PCME and Self-Diagno- sis Checker E+T 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 @r page F-7 Gartner Banana

TROUBLESHOOTING GUIDE INSPECTION ACTION :heck for correct intake manifold vacuum at idle Iacuum: More than 450 mmHg i17.7 inHg} VACUUM GAUGE / :heck if air cleaner element is clean page F-76 Check for fuel injector operating sound at idle Check if battery positive voltage exists at fuel injec- tor connector B terminal Check if PCME terminal voltages are OK (1 R, 1 T, 2D, 20 and 2Q) page F-146 Check for correct fuel line pressure at idle page F-110 Fuel line pressure: 265--314 kPa i2.7-3.2 kgf/cm2, 38-46 psi) (Vacuum hose to pressure regulator discon- nected) INSTALL CLAPS Yes - No Yes - No - Yes No - Yes Yes No - Yes - No Go to next step -- - --- Check for air leakage of intake air system components r@= page F-100 Go to next step Replace air cleaner element ~8 page F-99 Go to Step 14 Go to Step 13 check if fuel injector resistance is OK page F-119 Resistance: 12-16R 6 If OK, check wiring between PCME and fuel injector E+Y page F-7 6 If not OK, check fuel injector for fuel leakage page F-120 Check wiring between PCME and fuel injector page F-7 Go to next step Check for cause (Refer to "Check Point for Each Termi- nal") page F-148 Check if fuel line pressure decreases when accelerating quickly c:, If decreases, check fuel pump maximum pressure @r page F-115 If OK, check fuel line and filter for clogging o If no decreases, go to next step Low pressure Check fuel line pressure while pinching fuel return hose ~2 If fuel line pressure quickly increases, check pressure regulator I@= page F-118 o If fuel line pressure gradually increases, check for clog- ging between fuel pump and pressure regulator r@= page F-119 If not clogged, check fuel pump maximum pressure page F-115 Gartner Banana

TROUBLESHOOTING GUIDE INSPECTION Run engine at idle and check if fuel line pressure is held after ignition switch turned OFF page F-109 Fuel line pressure: More than 147 kPa (1.5 kgflcm2,21 psi) for 5 min. PRESSURE IGNITION 5 MIN. TIME SWITCH OFF Disconnect each fuel injector connector at idle and check if engine speed decreases equally each time Yes - No Yes ACTION High pressure Check if vacuum hose to pressure regulator is damage or poorly connected 6 If OK, replace pressure regulator page F-1 0 If not OK, repair or replace hose Check fuel injector for fuel leakage ~8 page F-1 Go to next step Replace fuel injector a page F: Try known good PCME and check if condition im- mwes page F-144 FEO Gartner Banana