fuel MAZDA MX-5 1994 Service Manual

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 )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

TROUBLESHOOTING GUIDE INSPECTION Check if "00" is displayed on Self-Diagnosis Check- er with ignition switch ON page F-79 14 - -- Check for correct idle speed page F-77 IDLE MOVES UP AND DOWN Idle speed: 850 2 50 rpm (MT) 800 + 50 rpm (AT) GND TEN I DESCRIPTION I Engine speeds up and down periodically at idle [TROUBLESHOOTING HINTS] O Fuel cut occurs at idle O Air leakage of intake air system Air valve not closing after warm-up and idle speed @ Poor ignition spark reaches to fuel cut speed 8 AirIFuel mixture too rich Q Fuel injection amount fluctuating Fuel evaporative system malfunction Bad contact point inside mass airflow sensor 8 Low engine compression 5'=€% CONNECT TERMINAL AIR ADJUSTING SCREW Check for correct ignition timing at idle * page F-76 Ignition timing: 10" 2 lo BTDC - Yes - No - Yes - No Yes ACTION Go to next step Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) @r page F-81 "88" flashes Check PCME terminal 1 E voltage re page F-145 Specification: Battery positive voltage (Ignition switch ON) 3 If OK, replace PCME page 6143 3 If not OK, check wiring between PCME and Self-Diagno- sis Checker page F-7 So to next step 2heck if idle speed can be adjusted by turning air adjust ;crew 3 If OK, adjust idle speed 3 If not OK, check air valve page F-105 20 to next step idjust I@= page F-76 Gartner Banana

TROUBLESHOOTING GUIDE - TEP - 4 INSPECTION ACTION ;heck for correct intake manifold vacuum at idle Yes - No - Yes Go to next step Intake manifold vacuum: More than 450 mmHg I17.7 InHg} ,VACUUM GAUGE Low vacuum Check for air leakage of intake air system page F-100 Zheck for fuel injector operating sound at idle with sound scope or screwdriver Go to Step 7 Go to Step 6 Check if fuel injector resistance is OK us page F-119 Check if battery positive voltage exists at fuel injec- tor connector B terminal Yes - No - Yes - No Resistance: 12-1 6R e If OK, check wiring between PCME and fuel injector page F-7 Q If not OK, replace fuel injector us page F-119 Check wiring between PCME and fuel injector page F-7 Disconnect each fuel injector connector at idle and check if engine speed decreases equally each time Disconnect each high-tension lead at idle and :heck if engine speed decreases equally each time Q If OK, go to Step 9 Q If not OK, check fuel injector for fuel leakage page F-120 Go to step 8 Zheck if spark plugs are OK ILDUP PLUG GAP 1.0-l.lmrn [0.04-.043 in) DAMAGE AND DETERIORATION Check if PCME terminal voltages are OK (1 R, IT, 2Q2Q and 2X) page F-146 Yes - No - Yes Check for correct engine compression Section B + If OK, replace fuel injector page F-119 Q If not OK, check for cause (Refer to Section 6) Section B Repair, clean, or replace Go to next step No - Yes Check for cause (Refer to "Check Point for Each Termi- nal") page F-148 Check purge solenoid valve = page F-132 - - Check if vacuum is felt at purge solenoid valveat Go to next step Try known good PCME and check if condition im- proves page F-144 Gartner Banana

TROUBLESHOOTING GUIDE FROUBLESHOOTING HINTS] O Incorrect idle speed ldle speed misadjustment ldle speed control malfunction 15 Q AirIFuel mixture too rich or lean Injector clogged or inoperative Low fuel line pressure ENGINE STALLS AT IDLE - ALWAYS Low intake ai; amount or air leakage Q Poor ianition s~ark DESCRIPTION I Engine starts normally but vibrates excessively and stalls at idle in every condition INSPECTION ;heck for correct intake manifold vacuum at idle Vacuum: More than 450 mmHg f17.7 inHg) VACUUM GAUGE / :heck if air cleaner element is clean @S page F-76 ?heck if "00" is displayed on Self-Diagnosis Check- 3r with ignition switch ON page F-79 SELECT SW A MONITOR . SYSTEM SELECT 1 ;heck switches for correct operation with Self- liagnosis Checker Monitor Lamp and ignition ;witch ON page F-95 SELECT SWA SYSTEM SELECT 1 - Yes - No Yes - No Yes No - Yes - No Go to next step ACTION Check for air leakage of intake air system components * page F-1 00 Go to next step Replace air cleaner element K@- page F-99 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 @a page F-145 Specification: Battery positive voltage (Ignition switch ON) 6 If OK, replace PCME @a page F-143 .r, 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 @f page F-7 Gartner Banana

TROUBLESHOOTING GUIDE INSPECTION ACTION ;heck if PCME terminal voltages are OK 1 R, IT, 20.20 and 2Q) page F-146 :heck if strong blue spark is visible at each discon- iected high-tension lead while cranking engine ;heck for fuel injector operating sound at each fuel njector at idle ;heck if battery positive voltage exists at fuel injec- :or connector B terminal :heck if spark plugs are OK PLUG GAP 14-1 .l mm (0.040-4.043 in) DAMAGE AND DETERIORATION :heck for EGR system malfunction uz page F-124 Yes No - Yes - No - Yes No - Yes - No - Yes No - Yes - No - Go to next step Check for cause (Refer to "Check Point for Each Termi- nal") @&T page F-148 Go to next step Check ignition system (Refer to Troubleshooting "Misfire") I@? Section G Go to Step 9 Go to Step 8 Check if fuel injector resistance is OK @&T page F-119 Resistance: 12-1 6R o If OK, check wiring between PCME and fuel injector page F-7 0 If not OK, replace fuel injector @&T page F-119 Check wiring between PCME and fuel injector I@? page F-7 Go to next step Repair or replace Section G Repair or replace Go to next step Gartner Banana

TROUBLESHOOTING GUIDE STEP 11 - 12 -- INSPECTION Sonnect data link connector terminals F/P and 3ND with jumper wire and check for correct fuel ine pressure with ignition switch ON page FllO Fuel line pressure: 265-314 kPa (2.7-3.2 kgflcm2, 38-46 psi) - Yes GND FIP INSTALL CLAPS ' I Try known good PCME and check if condition im- proves Daae F-144 ACTION 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 Q 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 Gartner Banana

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