fuel consumption MAZDA MX-5 1994 Workshop Manual

OUTLINE, TROUBLESHOOTING GUIDE OUTLINE SPECIFICATIONS Engine Item Tv~e BP DOHC Gasoline, 4-cvcle . . I -, Dis~lacement ml kc. cu inl I 1.840 (1.840. 11 2) I Cylinder arrangement and number Combustion chamber Valve system Bore x stroke mm {in) I 83.0 x 85.0 (3.27 x 3.35) I In-line, 4-cylinders Pentroof DOHC, belt-driven Com~ression ratio I 9.0 I Compression pressure kPa (kgf/cm2, psi)-rpm .- . 1 open (BTDCO) 1,255 {I 2.8, 182)-300 5 Valve timing TROUBLESHOOTING GUIDE tX Valve clearance Problem .. . -. . Difficult starting ' With System Selector (49 B019 9AO) test switch at SELF TEST. 45uo~x-003 Close (ATDCO) IN mm {in) EX mm {in) Poor idling Close (ABDCO) Open (BBDCO) 14 0: Maintenance-free 0: Maintenance-free Excessive oil consumption 48 56 Possible Cause Malfunction of engine-related components Burned valve Worn piston, piston ring, or cylinder Failed cylinder head gasket Malfunction of fuel system Malfunction of ignition system Malfunction of engine-related components Malfunction of HLA' Poor valve-to-valve seat contact Failed cvlinder head aasket Oil leakage I Refer to section D I I Remedy Malfunction of fuel system Malfunction of ignition system Oil working up Worn piston ring groove or sticking piston ring Worn piston or cylinder Oil working down Worn valve seal Worn valve stem or guide Page Replace Replace or repair Replace Refer to section F Refer to section G Replace Replace or repair Re~lace 8-48 B-53,55 B-1 6 B-20 B-50 B-1 6 Refer to section F Refer to section G Replace Replace or repair Replace Replace B-55 B-53,55 B-39,70 8-48 Gartner Banana

TROUBLESHOOTING GUIDE DIAGNOSTIC INDEX Cranks normally but will not start (No com- Engine cranks at normal speed but shows no sign of bustion) I #firingN I F-17 I No. 1 TROUBLESHOOTING ITEM Will not crank or cranks slowly -- -- Cranks normally but will not start (Partial combustion) -When engine is cold Cranks normally but will not start (Partial combustion) - After warm-up Cranks normally but hard to start - Always Cranks normally but hard to start - When engine is cold - Engine cranks at normal speed but shows partial com- bustion and will not continue to run Engine cranks at normal speed but shows partial com- bustion and will not continue to run after running and hot soaked Engine cranks at normal speed but requires excessive cranking time (more than 5 sec.) before starting Same condition as No.5 when engine is cold Restarts OK after warm-up 8 DESCRIPTION Refer to Engine Electrical System Low idle speed1Rough idle - Before warm- UP Low idle speed/Rough idle -After warm-up PAGE SECTION G Cranks normally but hard to start - After warm-up Rough idle - Always Engine speed low or engine vibrates excessively at idle during warm-up Engine runs normally at idle during warm-up but vi- brates excessively after warm-up High idle speed - After warm-up Low idle speed - When NC, PIS, or EIL ON l5 1 Engine stalls at idle - Always Engine starts normally but vibrates excessively and stalls at idle in every condition I F40 1 13 14 Same condition as No.5 after running and hot soaked Starts normally when cold Engine vibrates excessively at idle in every condition Engine idle excessive for operation mode Engine speed decreases at idle when NC, PIS, or EIL is ON 18 1 Engine stalls during start-up 1 Engine unexpectedly stops running while starting I F-45 F-26 F-27 F-34 F-36 Rough idle just after starting Idle moves up and down 16 17 l9 1 Engine stalls on deceleration I Engine unexpectedly stops running while decelerating or after deceleration Engine starts normally but vibrates excessively only just after starting Engine speed up and down periodically at idle Engine stalls at idle - Before warm-up Engine stalls at idle - After warm-up Engine stalls at idle -When AIC, PIS, or EIL running at idle when 1 20 1 ON I F-50 1 F-37 F-38 I I . . I 21 1 Engine stalls suddenly (Intermittent) I Engine intermittently stops running I F-52 Engine starts normally but vibrates excessively and stalls at idle before warm-up Engine runs normally at idle during warm-up but be- comes rouclh and stalls after warm-up F-43 F-44 24 1 Lack of power Performance is poor under load Maximum speed re- 1 duced I F-57 I Hesitates/Stumbles on acceleration Surges while cruising I I I 25 / Poor acceleration I Performance is poor while accelerating 1 F-61 I Flat spot occurs just after accelerator is depressed or mild jerking occurs during acceleration Unexpected, usually repetitive change in engine speed Knocking F-53 F-55 Runs rough on deceleration1Afterburn Abnormal combustion accompanied by audible "ping- ing" noise I F-67 I Engine runs rough while decelerating and abnormal combustion in exhaust system 1 30 1 High oil consumption I Oil consumption excessive I F-70 1 F-65 28 1 Fuel odor 29 / Exhaust sulfur smell 1 31 1 Poor fuel economy I Fuel economy unsatisfactory I F-71 I Gasoline odor in cabin Exhaust gas smells abnormal (rotten egg smell) F-69 F-70 Gartner Banana

F TROUBLESHOOTING GUIDE I [TROUBLESHOOTING HINTS] Hinh sulfur content fuel used 29 ISTEP l INSPECTION I ACTION I EXHAUST SULFUR SMELL I 1 I Chanae fuel to another brand I DESCRIPTION I Exhaust gas smells abnormal (Rotten egg smell) 30 I HIGH OIL CONSUMPTION TROUBLESHOOTING HINTS] D PCV system malfunction ne malfunction (Oil working up, working down, or leakage) INSPECTION Check if PCV hose, ventilation hose or their attach- ing nipples are separated, damaged, clogged, or restricted L@? page F-130 Check if air pressure or oil is present at ventilation hose VENTILATION Check if vacuum is felt at PCV valve at idle page F-130 Yes - No - Yes No - Yes ACTION Repair or replace e page F-122 Go to next step Go to next step Check engine condition Oil leakage Worn valve seal Worn valve stem Worn valve guide Section B Check engine condition Section B Worn piston ring groove Stuck piston ring Worn piston or cylinder Replace PCV valve page F-130 Gartner Banana

TROUBLESHOOTING GUIDE F POOR FUEL ECONOMY I [TROUBLESHOOTING HINTS] Nhile fuel consumption is drastically increased during city driving, short-run operation, stop and go driving, extended winterwarm- ~p periods, etc., as opposed to "trip" mileage, an attempt should be made to determine these factors when confronted with "poor mileage" conditions. However, since the operator is not always at fault, the following is offered. 3 Operator depressing accelerator more than usual due to O Alcohol blended fuel used low engine power @ High vehicle load Poor ignition Low tire pressure Low intake air amount Unrecommended tire used Electric spark advance control malfunction Brake dragging Clutch slipping @ Fuel cut control malfunction Exhaust component restricted @ High idle speed AirIFuel mixture too rich High fuel line pressure INSPECTION Check factors other than engine Low tire pressure Section Q Unrecommended tire used @zT Section Q Clutch slipping Section H Brake dragging Section P Exhaust component restricted @zT page F-128 ACTION - Yes Go to next step Repair Check if air hoses are connected correctly @zT page F-99 Yes - No Go to next step Repair @zT page F-99 Check if air cleaner element is clean page F-76 Yes - No Go to next step Replace page 699 Check if "00" is displayed on Self-Diagnosis Check- er with ignition switch ON @zT page F-79 Yes Go to next step SELECT SW A SYSTEM SELECT 1 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) 6 If OK, replace PCME page F-143 6 If not OK, check wiring between PCME and Self-Diagno- sis Checker page F-7 Check switches for correct operation with Self- Diagnosis Checker Monitor Lamp and ignition switch ON page F-95 SELECT SW A Yes Go to next step ~~p Lamp not ONIOFF with specified switch Check for cause (Refer to specified check sequence) @zT page F-96 Lamp always ON Check wiring between PCME terminal 1 F and Self-Diag- nosis Checker us page F-7 Gartner Banana