23 · Diagnostics

Excessive fuel consumption

Make: Alfa Romeo
Model: 159 Factory Service Manual
Year: 2005–2011
Section: Consumption /leaks/ wear › Excessive fuel consumption

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Fault diagnosisExcessive fuel consumption

EXCESSIVE FUEL CONSUMPTION

1.8, 1.9 JTS, 2.2 JTS

The fuel consumption, measured during an actual driving cycle, is considerably higher than expected. In addition, it is considerably higher than previously on the same vehicle during an actual driving cycle.

0	PRELIMINARY CHECKS	All OK	Problems encountered	Operation
		Test results
	Check that no accessories have been fitted in the after-market. Also check that the tyre inflation pressure is correct. Check the normal driving conditions, asking the customer whether: - the climate control and the electric defrosting are used often - heavy loads are often transported - the vehicle often travels at high rotation speeds or acceleration - the vehicle is used for towing other vehicles or a trailer	Move on to Step 1	Accessories have been fitted in the after-market	Check that these accessories have been correctly installed
		Move on to Step 1	The vehicle is often used in conditions requiring increased effort	Explain to the customer that the theoretical consumption figures refer to a vehicle that is used in standard conditions and not harsh conditions: in the latter case, the consumption figures could be considerably higher
1	CONTROL UNIT ELECTRICAL CONNECTIONS CHECK	All OK	Problems encountered	Operation
	Check that the engine management control unit electrical connections are correct See E5030 PETROL ENGINES ELECTRONIC MANAGEMENT	Move on to Step 2	Connections not correct	Restore the correct connections
2	CONTROL UNIT FASTENING CHECK	All OK	Problems encountered	Operation
	Check that the control unit is correctly fastened in its housing Op. 1056F82 CONTROL UNIT SINGLE OF INJECTION IGNITION SYSTEM R R	Move on to Step 3	Control unit fastening incorrect	Renew the correct fastening of the control unit Op. 1056F82 CONTROL UNIT SINGLE OF INJECTION IGNITION SYSTEM R R
3	AIR INTAKE CIRCUIT CHECK	All OK	Problems encountered	Operation
	Check there are no faults in the air intake circuit. In particular, check: - that the air filter is not blocked or fitted incorrectly - that the air intake circuit has no irregular constrictions, leaks or is incorrectly fitted	Move on to Step 4	Air filter blocked	Replace the filter element Op. 1048A14 AIR CLEANER FILTER ELEMENT - REPLACE.
			Faulty component	Replace the faulty component Op. 1048 ENGINE AIR SUPPLY CIRCUIT
			Component incorrectly fitted	Refit the component correctly Op. 1048 ENGINE AIR SUPPLY CIRCUIT
4	CHECK FOR THE PRESENCE OF IMPURITIES IN THE FUEL	All OK	Problems encountered	Operation
	Check that there are no impurities such as water, alcohol or particles in suspension in the fuel by carrying out the See T FUEL QUALITY CHECK	Move on to Step 5	There are faults present	The operation to solve the problem is described in the actual test
5	FUEL FEED CIRCUIT CHECK	All OK	Problems encountered	Operation
	Check there are no faults in the fuel supply circuit by performing the See Test 1040OA FUEL SUPPLY CIRCUIT CHECK	Move on to Step 6	There are faults present	The operation to solve the problem is described in the actual test
6	INJECTOR CHECK	All OK	Problems encountered	Operation
	Check that the injectors are not stuck shut or not perfectly closed, by carrying out the See Test 1056BA INJECTOR OPERATION CHECK	Move on to Step 7	There are faults present	The operation to solve the problem is described in the actual test
7	THROTTLE CASING CHECK	All OK	Problems encountered	Operation
	Check that the throttle body does not have an accumulation of material that is preventing it from closing properly	Move on to Step 8	There are impurities preventing the throttle casing from moving correctly	Clean or, if necessary, replace the throttle body Op. 1056F17 THROTTLE BODY WITH DVL R R
8	WHEEL CALIBRATION CHECK	All OK	Problems encountered	Operation
	Check that the ABS control unit signals that the correct size tyres have been fitted The use of larger or smaller tyres than the ones indicated can give a false speed reading for the ABS sensors and consequently affect the evaluation of the distance travelled and the consumption figures	Move on to Step 9	Different tyres to the ones indicated have been installed	Correct the type of tyres indicated in the ABS control unit, entering the type actually fitted. If the correct type of tyre has not been fitted, make sure that is is
9	DETONATION SENSOR ERRORS CHECK	All OK	Problems encountered	Operation
	Connect the diagnostic equipment and check that none of the following errors is present: P0325, P0330	Move on to Step 10	One or more of the errors indicated is present	Continue as described by the diagnostic equipment
10	IGNITION COIL CHECK	All OK	Problems encountered	Operation
	Check that the ignition coils are correctly fitted in their seats. Also check that they do not show signs of corrosion or dampness. Lastly, check that the ignition coils are working properly, by carrying out the See Test 5510CC IGNITION COIL CHECK	Move on to Step 11	One of the coils on the left cylinder head is not fitted correctly	Refit the coil correctly Op. 5510C14 IGNITION COIL/S - R.R.
			One of the coils on the right cylinder head is not fitted correctly	Refit the coil correctly Op. 5510C14 IGNITION COIL/S - R.R.
			One of the coils on the left cylinder head shows signs of corrosion/dampness	Replace the coil Op. 5510C14 IGNITION COIL/S - R.R.
			One of the coils on the right cylinder head shows signs of corrosion/dampness	Replace the coil Op. 5510C14 IGNITION COIL/S - R.R.
			One of the coils is not working properly	The operation to solve the problem is described in the actual test
11	SPARK PLUGS CHECK	All OK	Problems encountered	Operation
	Remove the spark plugs Op. 5510D10 SPARK PLUGS - R+R and check that there are no signs of faults, following the instructions in the See T SPARK PLUG STATE CHECK	Move on to Step 12	There are faults present	The operation to solve the problem is described in the actual test
12	ENGINE COOLING CHECK	All OK	Problems encountered	Operation
	Check the following, in order: - that there is sufficient engine coolant - that the engine coolant temperature sensor is working properly, by carrying out the See Test 1056BC ENGINE COOLANT TEMPERATURE SENSOR OPERATION CHECK	Move on to Step 13	Coolant fluid level insufficient	Top up the engine coolant Op. 0010T21 ENGINE COOLANT - CHECK DENSITY AND CHANGE, IF NECESSARY
		Move on to Step 13	Irreglar sensor operation	The operation to solve the problem is described in the actual test
13	CYLINDER COMPRESSION CHECK	All OK	Problems encountered	Operation
	Carry out the cylinder compression check Op. 0510A10 CYLINDER COMPRESSION - CHECK FOR LOOSE SPARK PLUGS OR INJECTORS	Move on to Step 15	Cylinder compression insufficient	Move on to Step 14
14	CHECK ON CAUSE OF INSUFFICIENT COMPRESSION	All OK	Problems encountered	Operation
	R/R the heads for the valve leakage test Op. 1016D10 CYLINDER HEAD – R.R. AND REPLACE GASKETS Check condition of cylinders/piston rings	Move on to Step 15	Valve seal insufficient	Overhaul the heads Op. 1016E20 CYLINDER HEAD (ONE), LEFT OR RIGHT, REMOVED - OVERHAUL
			Cylinders/piston rings worn	Restore the seal
			Cylinder head/cylinder block-crankcase matching faulty	Restore correct matching
15	TIMING CHECK	All OK	Problems encountered	Operation
	Check that the valve gear timing is correct Op. 0510A20 TIMING GEAR WITH BELT DRIVE - CHECK - CARRY OUT OPERATION WITH CAM COVER(S) REMOVED AND TAPPETS ADJUSTED AND CRANKSHAFT PULLEY DETACHED (IF NECESSARY)	Move on to Step 16	Valve gear timing not correct	Restore the correct valve gear timing
16	FOUR WHEEL DRIVE CHECK	All OK	Problems encountered	Operation
	Check that the four wheel drive does not remain activated constantly in conditions where it would not be necessary Travelling in conditions with four drive wheels rather than two increases fuel consumption	Move on to Step 17	The drive remains on constantly	Check the rear differential
17	EXHAUST SYSTEM CHECK	All OK	Problems encountered	Operation
	Check that the exhaust circuit has no leaks, looose connections, constrictions, deformations or damage	Move on to Step 18	There are faults present	Restore the correct fastening of problem components. Replace them if necessary
18	BRAKING SYSTEM CHECK	All OK	Problems encountered	Operation
	Check that none of the brakes (including the handbrake) is operated, in conditions where it would not be necessary Travelling in conditions where the wheels are partly or totally braked causes an increase in fuel consumption and can also lead to irregular wear of the tyres	Move on to Step 19	One or more of the brakes remains partly or totally applied	Continue as instructed in the See table F001 POOR BRAKING ACTION
		Move on to Step 19	The handbrake remains on constantly	Continue as instructed in the See table G002 HANDBRAKE LOCKED
19	CHECK ON CORRECT OPERATION	All OK	Problems encountered	Operation
	Check the fault has disappeared	End of diagnosis	The fault persists	Contact the Technical Expert for further information on the problem

3.2 JTS

0	PRELIMINARY CHECKS	All OK	Problems encountered	Operation
		Test results
	Check that no accessories have been fitted in the after-market. Also check that the tyre inflation pressure is correct. Check the normal driving conditions, asking the customer whether: - the climate control and the electric defrosting are used often - heavy loads are often transported - the vehicle often travels at high rotation speeds or acceleration - the vehicle is used for towing other vehicles or a trailer	Move on to Step 1	Accessories have been fitted in the after-market	Check that these accessories have been correctly installed
		Move on to Step 1	The vehicle is often used in conditions requiring increased effort	Explain to the customer that the theoretical consumption figures refer to a vehicle that is used in standard conditions and not harsh conditions: in the latter case, the consumption figures could be considerably higher
1	CONTROL UNIT ELECTRICAL CONNECTIONS CHECK	All OK	Problems encountered	Operation
	Check that the engine management control unit electrical connections are correct See E5030 PETROL ENGINES ELECTRONIC MANAGEMENT	Move on to Step 2	Connections not correct	Restore the correct connections
2	CONTROL UNIT FASTENING CHECK	All OK	Problems encountered	Operation
	Check that the control unit is correctly fastened in its housing Op. 1056F82 CONTROL UNIT SINGLE OF INJECTION IGNITION SYSTEM R R	Move on to Step 3	Control unit fastening incorrect	Renew the correct fastening of the control unit Op. 1056F82 CONTROL UNIT SINGLE OF INJECTION IGNITION SYSTEM R R
3	AIR INTAKE CIRCUIT CHECK	All OK	Problems encountered	Operation
	Check there are no faults in the air intake circuit. In particular, check: - that the air filter is not blocked or fitted incorrectly - that the air intake circuit has no irregular constrictions, leaks or is incorrectly fitted	Move on to Step 4	Air filter blocked	Replace the filter element Op. 1048A14 AIR CLEANER FILTER ELEMENT - REPLACE.
			Faulty component	Replace the faulty component Op. 1048 ENGINE AIR SUPPLY CIRCUIT
			Component incorrectly fitted	Refit the component correctly Op. 1048 ENGINE AIR SUPPLY CIRCUIT
4	CHECK FOR THE PRESENCE OF IMPURITIES IN THE FUEL	All OK	Problems encountered	Operation
	Check that there are no impurities such as water, alcohol or particles in suspension in the fuel by carrying out the See T FUEL QUALITY CHECK	Move on to Step 5	There are faults present	The operation to solve the problem is described in the actual test
5	FUEL FEED CIRCUIT CHECK	All OK	Problems encountered	Operation
	Check there are no faults in the fuel supply circuit by performing the See Test 1040OA FUEL SUPPLY CIRCUIT CHECK	Move on to Step 6	There are faults present	The operation to solve the problem is described in the actual test
6	INJECTOR CHECK	All OK	Problems encountered	Operation
	Check that the injectors are not stuck shut or not perfectly closed, by carrying out the See Test 1056BA INJECTOR OPERATION CHECK	Move on to Step 7	There are faults present	The operation to solve the problem is described in the actual test
7	THROTTLE CASING CHECK	All OK	Problems encountered	Operation
	Check that the throttle body does not have an accumulation of material that is preventing it from closing properly	Move on to Step 8	There are impurities preventing the throttle casing from moving correctly	Clean or, if necessary, replace the throttle body Op. 1056F17 THROTTLE BODY WITH DVL R R
8	WHEEL CALIBRATION CHECK	All OK	Problems encountered	Operation
	Check that the ABS control unit signals that the correct size tyres have been fitted The use of larger or smaller tyres than the ones indicated can give a false speed reading for the ABS sensors and consequently affect the evaluation of the distance travelled and the consumption figures	Move on to Step 9	Different tyres to the ones indicated have been installed	Correct the type of tyres indicated in the ABS control unit, entering the type actually fitted. If the correct type of tyre has not been fitted, make sure that is is
9	DETONATION SENSOR ERRORS CHECK	All OK	Problems encountered	Operation
	Connect the diagnostic equipment and check that none of the following errors is present: P0325, P0330	Move on to Step 10	One or more of the errors indicated is present	Continue as described by the diagnostic equipment
10	IGNITION COIL CHECK	All OK	Problems encountered	Operation
	Check that the ignition coils are correctly fitted in their seats. Also check that they do not show signs of corrosion or dampness. Lastly, check that the ignition coils are working properly, by carrying out the See Test 5510CC IGNITION COIL CHECK	Move on to Step 11	One of the coils on the left cylinder head is not fitted correctly	Refit the coil correctly Op. 5510C14 IGNITION COIL/S - R.R.
			One of the coils on the right cylinder head is not fitted correctly	Refit the coil correctly Op. 5510C14 IGNITION COIL/S - R.R.
			One of the coils on the left cylinder head shows signs of corrosion/dampness	Replace the coil Op. 5510C14 IGNITION COIL/S - R.R.
			One of the coils on the right cylinder head shows signs of corrosion/dampness	Replace the coil Op. 5510C14 IGNITION COIL/S - R.R.
			One of the coils is not working properly	The operation to solve the problem is described in the actual test
11	SPARK PLUGS CHECK	All OK	Problems encountered	Operation
	Remove the spark plugs Op. 5510D10 SPARK PLUGS - R+R and check that there are no signs of faults, following the instructions in the See T SPARK PLUG STATE CHECK	Move on to Step 12	There are faults present	The operation to solve the problem is described in the actual test
12	ENGINE COOLING CHECK	All OK	Problems encountered	Operation
	Check the following, in order: - that there is sufficient engine coolant - that the engine coolant temperature sensor is working properly, by carrying out the See Test 1056BC ENGINE COOLANT TEMPERATURE SENSOR OPERATION CHECK	Move on to Step 13	Coolant fluid level insufficient	Top up the engine coolant Op. 0010T21 ENGINE COOLANT - CHECK DENSITY AND CHANGE, IF NECESSARY
		Move on to Step 13	Irreglar sensor operation	The operation to solve the problem is described in the actual test
13	CYLINDER COMPRESSION CHECK	All OK	Problems encountered	Operation
	Carry out the cylinder compression check Op. 0510A10 CYLINDER COMPRESSION - CHECK FOR LOOSE SPARK PLUGS OR INJECTORS	Move on to Step 15	Cylinder compression insufficient	Move on to Step 14
14	CHECK ON CAUSE OF INSUFFICIENT COMPRESSION	All OK	Problems encountered	Operation
	R/R the heads for the valve leakage test Op. 1016D10 CYLINDER HEAD – R.R. AND REPLACE GASKETS Check condition of cylinders/piston rings	Move on to Step 15	Valve seal insufficient	Overhaul the heads Op. 1016E20 CYLINDER HEAD (ONE), LEFT OR RIGHT, REMOVED - OVERHAUL
			Cylinders/piston rings worn	Restore the seal
			Cylinder head/cylinder block-crankcase matching faulty	Restore correct matching
15	TIMING CHECK	All OK	Problems encountered	Operation
	Check that the valve gear timing is correct Op. 0510A20 TIMING GEAR WITH BELT DRIVE - CHECK - CARRY OUT OPERATION WITH CAM COVER(S) REMOVED AND TAPPETS ADJUSTED AND CRANKSHAFT PULLEY DETACHED (IF NECESSARY)	Move on to Step 16	Valve gear timing not correct	Restore the correct valve gear timing
16	FOUR WHEEL DRIVE CHECK	All OK	Problems encountered	Operation
	Check that the four wheel drive does not remain activated constantly in conditions where it would not be necessary Travelling in conditions with four drive wheels rather than two increases fuel consumption	Move on to Step 17	The drive remains on constantly	Check the rear differential
17	EXHAUST SYSTEM CHECK	All OK	Problems encountered	Operation
	Check that the exhaust circuit has no leaks, looose connections, constrictions, deformations or damage	Move on to Step 18	There are faults present	Restore the correct fastening of problem components. Replace them if necessary
18	BRAKING SYSTEM CHECK	All OK	Problems encountered	Operation
	Check that none of the brakes (including the handbrake) is operated, in conditions where it would not be necessary Travelling in conditions where the wheels are partly or totally braked causes an increase in fuel consumption and can also lead to irregular wear of the tyres	Move on to Step 19	One or more of the brakes remains partly or totally applied	Continue as instructed in the See table F001 POOR BRAKING ACTION
		Move on to Step 19	The handbrake remains on constantly	Continue as instructed in the See table G002 HANDBRAKE LOCKED
19	CHECK ON CORRECT OPERATION	All OK	Problems encountered	Operation
	Check the fault has disappeared	End of diagnosis	The fault persists	Contact the Technical Expert for further information on the problem

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