Engine Symptom Diagnosis

Perform troubleshooting referring to the following table when ECM (PCM) has detected no DTC and no abnormality has been found "VISUAL INSPECTION " in and "ENGINE BASIC CHECK ".

SYMPTOM DESCRIPTION CHART

Condition	Possible cause	Correction / Reference Item
Hard starting (Engine cranks OK)	Faulty idle air control system	Refer to " DTC P0505 / P0506 / P0507: IDLE CONTROL SYSTEM / RPM LOWER THAN EXPECTED / RPM HIGHER THAN EXPECTED " .
	Fault ECT sensor or MAF sensor	Refer to " ENGINE COOLANT TEMPERATURE (ECT) SENSOR INSPECTION " or " MASS AIR FLOW (MAF) SENSOR ON-VEHICLE INSPECTION " .
	Faulty ECM (PCM)	Refer to " INSPECTION OF ECM (PCM) AND ITS CIRCUITS " .
	Low compression	Refer to " COMPRESSION CHECK ".
	Faulty hydraulic valve lash adjuster	Refer to " VALVE LASH ADJUSTERS INSPECTION " .
	Compression leak from valve seat	Refer to " VALVES AND VALVE GUIDES INSPECTION " .
	Sticky valve stem	Refer to " VALVES AND VALVE GUIDES INSPECTION " .
	Weak or damaged valve springs	Refer to " VALVE SPRINGS INSPECTION " .
	Compression leak at cylinder head gasket	Refer to " CYLINDER HEAD INSPECTION " .
	Sticking or damaged piston ring	Refer to " CYLINDERS, PISTONS AND PISTON RINGS INSPECTION " .
	Worn piston, ring or cylinder	Refer to " PISTON PINS AND CONNECTING RODS INSPECTION " .
	Malfunctioning PCV valve	Refer to " PCV VALVE INSPECTION " .
Engine has no power	Engine overheating	Refer to condition of "Overheating".
	Defective spark plug.	Refer to " SPARK PLUG INSPECTION " .
	Faulty ignition coil with ignitor	Refer to " IGNITION COIL ASSEMBLY (IGNITER AND IGNITION COIL) INSPECTION " .
	Fuel pressure out of specification Dirty fuel filter Dirty or clogged fuel hose or pipe Malfunctional fuel pressure regulator Malfunctional fuel pump	Refer to " FUEL PRESSURE CHECK " .
	Maladjusted TP sensor installation angle	Refer to " THROTTLE POSITION (TP) SENSOR ADJUSTMENT " .
	Faulty EGR system	Refer to " DTC P0401 / P0402: EXHAUST GAS RECIRCULATION (EGR) FLOW INSUFFICIENT DETECTED /EXCESSIVE DETECTED " .
	Faulty injector	Refer to " FUEL INJECTOR INSPECTION " .
	Faulty TP sensor, ECT sensor or MAF sensor	Refer to " THROTTLE POSITION (TP) SENSOR ON-VEHICLE INSPECTION ", " ENGINE COOLANT TEMPERATURE (ECT) SENSOR INSPECTION " or " MASS AIR FLOW (MAF) SENSOR ON-VEHICLE INSPECTION " .
	Faulty ECM (PCM)	Refer to " INSPECTION OF ECM (PCM) AND ITS CIRCUITS " .
	Low compression.	Refer to " COMPRESSION CHECK " .
	Dragging brakes	Refer to condition: "Dragging brakes" in " BRAKES SYMPTOM DIAGNOSIS " .
	Slipping clutch	Refer to condition: "Slipping clutch" in " CLUTCH (HYDRAULIC TYPE) SYMPTOM DIAGNOSIS " .
Improper engine idling or engine fails to idle	Faulty spark plug	Refer to " SPARK PLUG INSPECTION " .
	Faulty ignition coil with ignitor	Refer to " IGNITION COIL ASSEMBLY (IGNITER AND IGNITION COIL) INSPECTION " .
	Fuel pressure out of specification	Refer to " FUEL PRESSURE CHECK " .
	Engine overheating	Refer to condition of "Overheating" .
	Maladjusted TP sensor installation angle if adjustable	Refer to " THROTTLE POSITION (TP) SENSOR ADJUSTMENT " .
	Faulty idle air control system	Refer to " DTC P0505 / P0506 / P0507: IDLE CONTROL SYSTEM / RPM LOWER THAN EXPECTED / RPM HIGHER THAN EXPECTED " .
	Faulty evaporative emission control system	Refer to " DTC P0442/P0455: EVAPORATIVE EMISSION CONTROL SYSTEM LEAK DETECTED (SMALL LEAK) / (GROSS LEAK) " .
	Faulty EGR system	Refer to " DTC P0401/P0402: EXHAUST GAS RECIRCULATION (EGR) FLOW INSUFFICIENT DETECTED /EXCESSIVE DETECTED " .
	Faulty injector	Refer to " FUEL INJECTOR INSPECTION " .
	Faulty ECT sensor, TP sensor or MAF sensor	Refer to or " ENGINE COOLANT TEMPERATURE (ECT) SENSOR INSPECTION ", " THROTTLE POSITION (TP) SENSOR ON-VEHICLE INSPECTION " or " MASS AIR FLOW (MAF) SENSOR ON-VEHICLE INSPECTION " .
	Faulty ECM (PCM)	Refer to " INSPECTION OF ECM (PCM) AND ITS CIRCUITS " .
	Low compression	Refer to " COMPRESSION CHECK " .
	Malfunctioning PCV valve	Refer to " PCV VALVE INSPECTION " .
Engine hesitates (Momentary lack of response as the accelerator is depressed. Can occur at all vehicle speeds. Usually most severe when first trying to make the vehicle move, as from a stop sign.)	Spark plug faulty or plug gap as out of adjustment	Refer to " SPARK PLUG INSPECTION " .
	Fuel pressure out of specification Clogged fuel filter Faulty fuel pressure regulator	Refer to " FUEL PRESSURE CHECK " .
	Clogged fuel filter, hose or pipe	Refer to " FUEL PRESSURE CHECK ".
	Engine overheating	Refer to condition of "Overheating" .
	Faulty EGR system	Refer to " DTC P0401 / P0402: EXHAUST GAS RECIRCULATION (EGR) FLOW INSUFFICIENT DETECTED /EXCESSIVE DETECTED " .
	Faulty injector	Refer to " FUEL INJECTOR INSPECTION " .
	Faulty TP sensor, ECT sensor or MAF sensor	Refer to " THROTTLE POSITION (TP) SENSOR ON-VEHICLE INSPECTION ", " ENGINE COOLANT TEMPERATURE (ECT) SENSOR INSPECTION " or " MASS AIR FLOW (MAF) SENSOR ON-VEHICLE INSPECTION " .
	Faulty ECM (PCM).	Refer to " INSPECTION OF ECM (PCM) AND ITS CIRCUITS " .
	Low compression	Refer to " COMPRESSION CHECK " .
Surges (Engine power variation under steady throttle or cruise. Feels like the vehicle speeds up and down with no change in the accelerator pedal.)	Defective spark plug (excess carbon deposits, improper gap, and burned electrodes, etc.)	Refer to " SPARK PLUG INSPECTION " .
	Variable fuel pressure Clogged fuel filter Swirly or damaged fuel hose and line Faulty fuel pressure regulator	Refer to " FUEL PRESSURE CHECK " .
	Faulty EGR system	Refer to " DTC P0401 / P0402: EXHAUST GAS RECIRCULATION (EGR) FLOW INSUFFICIENT DETECTED /EXCESSIVE DETECTED " .
	Faulty MAF sensor	Refer to " MASS AIR FLOW (MAF) SENSOR ON-VEHICLE INSPECTION " .
	Faulty injector	Refer to " FUEL INJECTOR INSPECTION " .
	Faulty ECM (PCM)	Refer to " INSPECTION OF ECM (PCM) AND ITS CIRCUITS " .
Excessive detonation (The engine makes sharp metallic knocks that change with throttle opening. Sounds like pop corn popping.)	Engine overheating	Refer to condition of "Overheating" .
	Faulty spark plug	Refer to " SPARK PLUG INSPECTION " .
	Improper ignition timing	Refer to " IGNITION TIMING CHECK AND ADJUSTMENT " .
	Clogged fuel filter and fuel lines	Refer to " FUEL PRESSURE CHECK " .
	Faulty EGR system	Refer to " DTC P0401 /P0402: EXHAUST GAS RECIRCULATION (EGR) FLOW INSUFFICIENT DETECTED /EXCESSIVE DETECTED " .
	Faulty ECT sensor or MAF sensor	Refer to " ENGINE COOLANT TEMPERATURE (ECT) SENSOR INSPECTION " or " MASS AIR FLOW (MAF) SENSOR ON-VEHICLE INSPECTION " .
	Faulty injector	Refer to " FUEL INJECTOR INSPECTION " .
	Faulty ECM (PCM)	Refer to " INSPECTION OF ECM (PCM) AND ITS CIRCUITS " .
	Excessive combustion chamber deposits	Refer to " CYLINDER HEAD INSPECTION " and " CYLINDERS, PISTONS AND PISTON RINGS INSPECTION " .
Overheating	Inoperative thermostat	Refer to " THERMOSTAT INSPECTION " .
	Poor water pump performance	Refer to " WATER PUMP INSPECTION " .
	Clogged or leaky radiator	Refer to " RADIATOR INSPECTION AND CLEANING " .
	Improper engine oil grade	Refer to " ENGINE OIL AND FILTER CHANGE " .
	Clogged oil filter or oil strainer	Refer to " ENGINE OIL AND FILTER CHANGE " or " OIL PAN AND OIL PUMP STRAINER CLEANING " .
	Poor oil pump performance	Refer to " OIL PUMP INSPECTION " .
	Dragging brakes	Refer to condition: "Dragging brakes" in " BRAKES SYMPTOM DIAGNOSIS " .
	Slipping clutch	Refer to condition: "Slipping clutch" in " CLUTCH (HYDRAULIC TYPE) SYMPTOM DIAGNOSIS " .
	Blown cylinder head gasket	Refer to " CYLINDER HEAD INSPECTION " .
Poor gasoline mileage	Faulty spark plug (improper gap, heavy deposits, and burned electrodes, etc.)	Refer to " SPARK PLUG INSPECTION " .
	Fuel pressure out of specification	Refer to " FUEL PRESSURE CHECK " .
	Faulty TP sensor, ECT sensor or MAF sensor	Refer to " THROTTLE POSITION (TP) SENSOR ON-VEHICLE INSPECTION ", " ENGINE COOLANT TEMPERATURE (ECT) SENSOR INSPECTION " or " MASS AIR FLOW (MAF) SENSOR ON-VEHICLE INSPECTION " .
	Faulty EGR system	Refer to " DTC P0401 /P0402: EXHAUST GAS RECIRCULATION (EGR) FLOW INSUFFICIENT DETECTED /EXCESSIVE DETECTED " .
	Faulty injector	Refer to " FUEL INJECTOR INSPECTION " .
	Faulty ECM (PCM)	Refer to " INSPECTION OF ECM (PCM) AND ITS CIRCUITS " .
	Low compression	Refer to " COMPRESSION CHECK " .
	Poor valve seating	Refer to " VALVES AND VALVE GUIDES INSPECTION " .
	Dragging brakes	Refer to condition: "Dragging brakes" in " BRAKES SYMPTOM DIAGNOSIS " .
	Slipping clutch	Refer to condition: "Slipping clutch" in " CLUTCH (HYDRAULIC TYPE) SYMPTOM DIAGNOSIS " .
	Thermostat out of order	Refer to " THERMOSTAT INSPECTION " .
	Improper tire pressure	Adjust tire pressure.
Excessive engine oil consumption	Sticky piston ring	Refer to " CYLINDERS, PISTONS AND PISTON RINGS INSPECTION " .
	Worn piston and cylinder	Refer to " CYLINDERS, PISTONS AND PISTON RINGS INSPECTION " .
	Worn piston ring groove and ring	Refer to " CYLINDERS, PISTONS AND PISTON RINGS INSPECTION " .
	Improper location of piston ring gap	Refer to " PISTONS, PISTON RINGS, CONNECTING RODS AND CYLINDERS DISASSEMBLY AND ASSEMBLY " .
	Worn or damaged valve stem seal	Replace .
	Worn valve stem	Refer to " VALVES AND VALVE GUIDES INSPECTION " .
Low oil pressure	Improper oil viscosity	Refer to " ENGINE OIL AND FILTER CHANGE " .
	Malfunctioning oil pressure switch	Refer to " OIL PRESSURE SWITCH INSPECTION " .
	Clogged oil strainer	Refer to " OIL PAN AND OIL PUMP STRAINER CLEANING " .
	Functional deterioration of oil pump	Refer to " OIL PUMP INSPECTION " .
	Worn oil pump relief valve	Refer to " OIL PUMP INSPECTION " .
	Excessive clearance in various sliding parts
Engine noise NOTE: Before checking the mechanical noise, make sure that: Ignition timing is properly adjusted. Specified spark plug is used. Specified fuel is used.	Faulty hydraulic valve lash adjuster	Refer to " VALVE LASH ADJUSTERS INSPECTION " .
	Worn valve stem and guide	Refer to " VALVES AND VALVE GUIDES INSPECTION " .
	Weak or broken valve spring	Refer to " VALVE SPRINGS INSPECTION " .
	Warped or bent valve	Refer to " VALVES AND VALVE GUIDES INSPECTION " .
	Loose camshaft housing bolts	Refer to " CAMSHAFTS AND VALVE LASH ADJUSTERS REMOVAL AND INSTALLATION " .
	Worn piston, ring and cylinder bore	Refer to " CYLINDERS, PISTONS AND PISTON RINGS INSPECTION " .
	Worn crankpin bearing	Refer to " CRANK PINS AND CONNECTING ROD BEARINGS INSPECTION " .
	Worn crankpin	Refer to " CRANK PINS AND CONNECTING ROD BEARINGS INSPECTION " .
	Loose connecting rod nuts	Refer to " PISTONS, PISTON RINGS, CONNECTING RODS AND CYLINDERS REMOVAL AND INSTALLATION " .
	Low oil pressure	Refer to condition "Low oil pressure" previously described.
	Worn crankshaft journal bearing	Refer to " MAIN BEARINGS INSPECTION " .
	Worn crankshaft journal	Refer to " CRANKSHAFT INSPECTION " .
	Loose lower crankcase (bearing cap) bolts	Refer to " MAIN BEARINGS, CRANKSHAFT AND CYLINDER BLOCK REMOVAL AND INSTALLATION " .
	Excessive crankshaft thrust play	Refer to " CRANKSHAFT INSPECTION " .