Content .. 94 95 96 97 ..

Daewoo Matiz (2003 year). Service manual - part 96

1F – 294 ENGINE CONTROLS

CUTS OUT, MISSES

Definition: Steady pulsation or jerking that follows en-
gine speed, usually more pronounced as engine load in-

creases. The exhaust has a steady spitting sound at idle
or low speed.

Step

Action

Value(s)

Yes

Were the Important Preliminary Checks performed?

–

Go to Step 2

Go to

“Important

Preliminary

Checks”

Check the ignition system voltage output for all of
the cylinders using a spark tester.
Is spark present on all of the cylinders?

–

Go to Step 3

Go to “Ignition

System Check”

1. Inspect the spark plugs for excessive wear,

insulation cracks, improper gap, or heavy
deposits.

2. Check the resistance of the ignition wires.

Replace any ignition wires that have a resistance
greater than the value specified.

Is the problem found?

30000

Ω

Go to Step 4

Go to Step 5

Repair or replace any components as needed.
Is the repair complete?

–

System OK

–

With the engine running, spray the ignition wires with
a fine water mist to check for arcing and shorting to
ground.
Is the problem found?

–

Go to Step 6

Go to Step 7

Replace the ignition wires.
Is the repair complete?

–

System OK

–

1. Perform a cylinder compression test.
2. If the compression is low, repair the engine as

needed.

3. Inspect for proper valve timing, bent pushrods,

worn rocker arms, broken or weak valve springs,
and worn camshaft lobes.

4. Inspect the intake manifold and the exhaust

manifold passages for casting flash.

Is the problem found?

–

Go to Step 8

Go to Step 9

Repair or replace any components as needed.
Is the repair complete?

–

System OK

–

1. Check the fuel system for a plugged in-line fuel

filter.

2. Check the fuel system for low fuel pressure. If the

fuel pressure is below the value specified, service
the fuel system as needed.

3. Inspect for contaminated fuel.
Is the problem found?

380 kPa

(55 psi)

Go to Step 10

Go to Step 11

Repair or replace any components as needed.
Is the repair complete?

–

System OK

–

1. Disconnect all of the fuel injector harness

connectors at the fuel injectors.

2. Connect an injector test light to the harness

terminals of each fuel injector connector.

3. Note the test light while cranking the engine for

each fuel injector.

Does the test light blink for all of the fuel injectors?

–

Go to Step 13

Go to Step 12

ENGINE CONTROLS 1F – 295

Cuts Out, Misses (Cont’d)

Step

Action

Value(s)

Yes

1. Repair or replace the faulty injector drive circuit

harness, the connector, or the connector terminal.

2. If the connections and the harnesses are good,

replace the Engine Control Module (ECM).

Is the repair complete?

–

System OK

–

Measure the resistance of each fuel injector.
Is the injector resistance within the value specified
(the resistance will increase slightly at higher
temperatures)?

11.6–12.4

Ω

Go to Step 15

Go to Step 14

Replace any fuel injectors with a resistance that is
out of specifications.
Is the repair complete?

–

System OK

–

Perform an injector diagnosis.
Is the problem found?

–

Go to Step 16

Go to Step 17

Replace any restricted or leaking fuel injectors.
Is the repair complete?

–

System OK

–

1. Check for electromagnetic interference.
2. Monitor the engine rpm with a scan tool.
Does the scan tool rpm change greatly with little
change in actual engine rpm?

–

Go to Step 18

–

1. Inspect the routing of the ignition wires.
2. Inspect all of the ignition system grounds.
3. Correct the routing or repair the ground

connections as needed.

Are all checks and needed repairs complete?

–

System OK

–

1F – 296 ENGINE CONTROLS

POOR FUEL ECONOMY

Definition: Fuel economy, as measured by an actual
road test, is noticeably lower than expected. Also, fuel
economy is noticeably lower than it was on this vehicle
at one time, as previously shown by an actual road test.

Important: Driving habits affect fuel economy. Check
the owner’s driving habits by asking the following ques-
tions:

1. Is the A/C system (i.e. defroster mode) turned on all

the time?

2. Are the tires at the correct air pressure?

3. Have excessively heavy loads been carried?

4. Does the driver accelerate too much and too often?

Suggest the driver read the section in the owner’s
manual about fuel economy.

Step

Action

Value(s)

Yes

Were the Important Preliminary Checks performed?

–

Go to Step 2

Go to

“Important

Preliminary

Checks”

1. Inspect the air filter for excessive contamination.
2. Inspect for fuel system leaks.
Are all needed checks complete?

–

Go to Step 3

–

1. Inspect the spark plugs for excessive wear,

insulation cracks, improper gap, or heavy
deposits.

2. Replace any faulty spark plugs.
3. Inspect the ignition wires for cracking, hardness,

and proper connections.

Are all needed checks and repairs complete?

–

Go to Step 4

–

1. Inspect the engine coolant level.
2. Check the thermostat for being always open or for

an incorrect heat range.

3. Replace the thermostat as needed.
Are all needed checks and repairs complete?

–

Go to Step 4

–

1. Check the transaxle shift pattern. Ensure all

transaxle gears are functioning.

2. Check for proper calibration of the speedometer.
3. Check the brakes for dragging.
4. Check the cylinder compression.
5. Repair, replace, or adjust any components as

needed.

Are all checks and needed repairs complete?

–

System OK

–

ENGINE CONTROLS 1F – 297

ROUGH, UNSTABLE, OR INCORRECT IDLE, STALLING

Definition: The engine runs unevenly at idle. If the condi-
tion is bad enough, the vehicle may shake. Also, the idle
varies in rpm (called “hunting”). Either condition may be
severe enough to cause stalling. The engine idles at in-
correct idle speed.

Important: Before diagnosing the symptom, check ser-
vice bulletins for updates.

Step

Action

Value(s)

Yes

Were the Important Preliminary Checks performed?

–

Go to Step 2

Go to

“Important

Preliminary

Checks”

1. Connect the scan tool to the Data Link Connector

(DLC).

2. Monitor the oxygen sensor (O2S) reading at

different throttle positions.

Does the O2S change quickly from rich to lean at
the different throttle positions?

–

Go to Step 5

Go to Step 3

Check the O2S for contamination from fuel or
improper use of room temperature vulcanizing
sealant.
Is the O2S contaminated?

–

Go to Step 4

Go to Step 5

Replace the contaminated O2S as needed.
Is the repair complete?

–

System OK

–

1. Check for a sticking throttle shaft or binding

throttle linkage that may cause incorrect Throttle
Position (TP) sensor voltage.

2. Check the TP sensor voltage reading with the

throttle closed.

Is the TP sensor voltage within the value specified?

0.4–0.8 V

Go to Step 6

Go to

“Diagnostic

Aids for DTC

P0123”

1. Check the Engine Coolant Temperature (ECT)

sensor voltage reading using the scan tool.

2. Compare the ECT sensor reading with the

ambient temperature when the engine is cold.

Does the ECT sensor temperature reading differ
from the ambient temperature by more than the
value specified?

C (5

Go to Step 7

Go to Step 9

Check for high resistance in the ECT sensor circuit
or the sensor itself.
Is the problem found?

–

Go to Step 8

Go to Step 9

Replace the ECT sensor or repair the circuit as
needed.
Is the repair complete?

–

System OK

–

Check the Manifold Absolute Pressure (MAP)
sensor for response and accuracy.
Is the problem found?

–

Go to Step 10

Go to Step 11

Replace the MAP sensor or repair the MAP sensor
circuit as needed.
Is the repair complete?

–

System OK

–

1. Road test the vehicle at the speed of the

complaint.

2. Monitor the long term fuel trim reading using the

scan tool.

Is the long term fuel trim reading within the value
specified?

–20–25%

Go to Step 14

Go to Step 12

Content .. 94 95 96 97 ..