engine MAZDA MX-5 1994 Workshop Manual

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

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