Engine fault diagnostics (BMW 5 Series E28)

Symptom	Possible cause
The engine does not turn over when trying to start	The battery terminals are oxidized, or the wire ends are loose (see chapter Routine car maintenance).
	The battery is discharged or defective (see chapter Routine car maintenance).
	The automatic transmission was not properly put into the "P" position (see chapter Automatic transmission (AT)) or - on models with a clutch switch sensor - the clutch is not fully depressed (see chapter Clutch).
	The wiring of the starting system circuit is broken or otherwise damaged, or the fastening of the terminals of the contact connections is loose (see Chapters Ignition system and On-board electrical equipment system).
	The starter drive pinion teeth are jammed in the flywheel ring gear (see chapter Ignition system).
	The starter solenoid relay is faulty (see chapter Ignition system).
	The starter motor is faulty (see chapter Ignition system).
	The ignition switch is faulty (see chapter On-board electrical equipment system).
	The teeth of the starter drive pinion or flywheel ring gear are broken or worn out (see Chapters Engine and Engine management and emission control systems).
	There is internal engine damage (see section Engine Component Overhaul Procedures).
The engine turns over but does not start	The fuel tank is empty.
	The battery is discharged (the engine turns over too slowly) (See Chapter Ignition system).
	The battery terminals are oxidized, or the wire ends are loose (see chapter Routine car maintenance).
	There are fuel leaks through the injector, the fuel pump or pressure regulator is faulty, etc. (see chapter Power supply system).
	Fuel does not reach the injection system/carburetor (see chapter Power supply system).
	Ignition system components are wet or damaged (see chapter Ignition system).
	The fuel injector is stuck open (see chapter Power supply system).
	The spark plugs are worn or damaged, or the interelectrode gap setting is incorrect (see chapter Routine car maintenance).
	The wiring of the starting system circuit is broken or otherwise damaged, or the fastening of the terminals of the contact connections is loose (see chapter Ignition system).
	The distributor mounting bolts have become loose, which has resulted in failure to set the ignition timing (see Chapters Routine car maintenance and Ignition system).
	The ignition coil wiring is broken or otherwise damaged, or the terminals of the contact connections are loose (see Chapters Ignition system).
	The ignition coil is faulty (see chapter Ignition system).
Difficulty starting a cold engine	The battery is discharged (see chapter Routine car maintenance).
	The power supply system is not functioning properly (see chapter Power supply system).
	There is a leak through the injector, or the automatic starter is not functioning properly (see chapter Power supply system).
	Carbon tracks have formed on the distributor rotor (see chapter Ignition system).
Difficulty starting a hot engine	The air cleaner filter element is dirty or its flow is otherwise impaired (see chapter Routine car maintenance).
	Fuel does not reach the injection system/carburetor (see chapter Power supply system).
	The battery terminals are oxidized - special attention should be paid to the condition of the ground terminal (negative) (See Chapter Routine car maintenance).
The starter is difficult to engage or is accompanied by extraneous noises	The teeth of the starter drive pinion or flywheel ring gear are broken or worn out (see chapter Ignition system).
	The starter mounting bolts have come loose or fallen out (see chapter Ignition system).
The engine starts but immediately stalls	The terminal connections on the distributor, ignition coil or generator have become loose (see chapter Ignition system).
	The fuel supply to the injection system injectors/carburetor is faulty (see Chapters BMW 5-series cars and Power supply system).
	The fuel injection system speed sensors are faulty (see chapter Ignition system).
	The relay of the electrical circuit of the injection system is faulty (see chapter Ignition system).
Oil leaks form under the engine when the car is parked	There are leaks through the gasket and/or drain plug of the oil pan (see chapter Engine).
	There is a leak through the oil pressure sensor (see chapter Engine).
	There are leaks through the cylinder head cover gaskets (see chapter Engine).
	There are leaks through the engine shaft seals (see chapter Engine).
Idle speed stability is impaired	There are losses of vacuum (see chapter Power supply system).
	The air cleaner filter element is blocked (see chapter Routine car maintenance).
	The fuel pump does not supply the correct amount of fuel to the injection system/carburetor (see chapter Power supply system).
	The cylinder head gasket is leaking (see chapter Engine).
	The timing belt/chain or its toothed wheel/sprockets are worn out (see chapter Engine).
	The working projections of the camshaft cams are worn out (see chapter Engine).
	The carbon adsorber is faulty (if such is provided) (See Chapter Engine management and emission control systems).
There are misfires at idle speed	The spark plugs are worn or damaged, or the interelectrode gap setting is incorrect (see chapter Routine car maintenance).
	The spark plug wires are faulty (see chapter Routine car maintenance).
	There are losses of vacuum (see chapter Routine car maintenance).
	The ignition timing angle setting is incorrect (see chapter Ignition system).
	The compression pressure has dropped or is unevenly distributed between the cylinders (see chapter Engine).
	The carbon adsorber is faulty (if such is provided) (See Chapter Engine management and emission control systems).
Misfires occur when driving in gear	The fuel filter is clogged or the fuel system is contaminated (see chapter Routine car maintenance).
	The injectors do not provide adequate fuel injection, or the patency of the carburetor fuel jets is partially impaired (see chapter Power supply system).
	Spark plugs are worn or damaged, or the interelectrode gap setting is incorrect - petrol models (see chapter Routine car maintenance).
	The ignition timing angle setting is incorrect (see chapter Ignition system).
	The distributor cap is cracked, the high-voltage wires are disconnected, or other distributor components are damaged (see chapter Routine car maintenance).
	The spark plug wires are faulty (see chapter Routine car maintenance).
	The components of the emission control systems are faulty (see chapter Engine management and emission control systems).
	The compression pressure has dropped or is unevenly distributed between the cylinders (see chapter Engine).
	The ignition system is not functioning properly (see chapter Ignition system).
	There are losses of vacuum in the injection system, on the intake manifold or through the connecting hoses (see chapter Power supply system).
Misfires occur during engine acceleration	The spark plugs are faulty (see chapter Routine car maintenance).
	The injection/carburetor system is not functioning properly (see chapter Power supply system).
	The fuel filter is blocked (see Chapters BMW 5-series cars and Power supply system).
	The ignition timing angle setting is incorrect (see chapter Ignition system).
	There are air leaks through the intake manifold (see chapter Power supply system).
Engine speed increases spontaneously when the gas pedal is held stationary	There are intake air leaks (see chapter Power supply system).
	The fuel pump is faulty (see chapter Power supply system).
	The fuel injector wiring harness terminal connections have become loose (see Chapters Power supply system and Engine management and emission control systems).
	The electronic control unit (ECU) is faulty (see chapter Ignition system).
The engine power has dropped	The ignition timing angle setting is incorrect (see chapter Ignition system).
	Excessive play in the distributor shaft (see chapter Ignition system).
	The rotor or distributor cap or high voltage wires are worn out (see Chapters BMW 5-series cars and Ignition system).
	The spark plugs are faulty or the interelectrode gap adjustment is incorrect (see chapter Routine car maintenance).
	The injection/carburetor system is not functioning properly (see chapter Power supply system).
	The ignition coil is faulty (see chapter Ignition system).
	The brakes are stuck (see chapter Routine car maintenance).
	The automatic transmission fluid level has dropped (see chapter Routine car maintenance).
	The clutch slips (see chapter Clutch).
	The fuel filter is blocked and/or the fuel system is contaminated (see chapter Routine car maintenance).
	The functioning of the exhaust gas toxicity reduction systems is impaired (see chapter Engine management and emission control systems).
	The compression pressure has dropped or is unevenly distributed between the cylinders (see chapter Engine).
The engine stalls spontaneously	The idle speed setting is incorrect (see chapter Routine car maintenance).
	The fuel filter is clogged, or moisture or other contaminants have entered the fuel system (see chapter Routine car maintenance).
	The distributor components are damp or damaged (see chapter Ignition system).
	The components of the emission control systems are faulty (see chapter Engine management and emission control systems).
	The spark plugs are faulty or the interelectrode gap adjustment is incorrect (see chapter Routine car maintenance).
	The spark plug wires are faulty (see chapter Routine car maintenance).
	There are losses of vacuum in the injection system, on the intake manifold or through the connecting hoses - petrol models (see chapter Power supply system).
"Shots" occur in the exhaust system	The functioning of the exhaust gas toxicity reduction systems is impaired (see chapter Engine management and emission control systems).
	The ignition timing angle setting is incorrect (see chapter Ignition system).
	The secondary circuit of the ignition system is faulty (defects in spark plug insulators, high voltage wires, distributor cap and/or rotor) (See Chapter Ignition system).
	The fuel injection system/carburetor is not functioning properly (see chapter Power supply system).
	There are losses of vacuum in the injection system, on the intake manifold or through the connecting hoses - petrol models (see chapter Power supply system).
	The valve clearances are incorrectly set (see chapter Routine car maintenance), the valve may be damaged or jammed (see chapter Engine).
When accelerating the engine or driving uphill, detonation sounds occur	The car was filled with the wrong type of fuel.
	The ignition timing angle setting is incorrect (see chapter Ignition system).
	The fuel injection system/carburetor needs adjustment (see chapter Power supply system).
	The spark plugs or high voltage wires are damaged, or the wrong type of spark plugs may have been installed (see chapter Routine car maintenance).
	Distributor components are worn or damaged (see chapter Ignition system).
	The exhaust gas toxicity reduction system is faulty (see chapter Engine management and emission control systems).
	There are losses of vacuum (see chapter Power supply system).
The oil pressure warning light remains on after the engine has started successfully Stop the engine immediately and find out the cause of the failure. Operating the engine with low oil pressure can cause serious damage!	The oil level has dropped, or the wrong type of oil has been added (see chapter Routine car maintenance).
	Idle speed is too low (see chapter Routine car maintenance).
	There is a short circuit in the electrical wiring (see chapter On-board electrical equipment system).
	The oil pressure switch is faulty (see chapter Engine).
	Engine bearings and/or oil pump are worn out (see chapter Engine).
The engine continues to run after the ignition is turned off	The idle speed is too high (see chapter Routine car maintenance).
	The engine operating temperature is too high (see chapter Cooling system).
	The octane number of the fuel does not correspond to the technical characteristics of the engine.
	The spark plugs are faulty or the interelectrode gap adjustment is incorrect (see chapter Routine car maintenance).

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Article verified: Zhuravleva Isolda

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БМВ E28: Engine overhaul

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