fuse FORD FESTIVA 1991 Owner's Manual

COOLING FAN DOES NOT RUN WITH A/C ON
If cooling fan does not run with A/C on, check the following items to help isolate fault.
Check A/C cooling fan relay.
Check cooling fan wiring harness.
TESTING
VOLTAGE SUPPLY TEST
Disconnect cooling fan motor connector. Turn ignition on. Check for voltage at Yellow wire terminal of connector. If voltage is NOT present,
check for blown 20-amp COOLING fuse (Capri) or C-FAN fuse (Festiva) or open in Yellow wire between cooling fan and fuse.
Disconnect cooling fan relay connector. Cooling fan relay is located in the left front corner of engine compartment. Turn ignition on. Check
for voltage at Yellow (Capri) or Black/Yellow (Festiva) wire terminal of connector. If voltage is NOT present, check for blown 30-amp
HEATER fuse on Capri or 10-amp METER fuse on Festiva or open in Black/Yellow wire between cooling fan relay and fuse.
Disconnect A/C cooling fan relay connector. On Capri, A/C relay is located in the left rear corner of the engine compartment, on firewall. On
Festiva, A/C relay is located in the left front corner of engine compartment, under a triple relay cover. Relay may be identified by wire colors
to relay connector. See Fig. 2
and Fig. 3 . Turn ignition on. Check for voltage at Blue wire terminal of connector. If voltage is NOT present,
check for blown 15-amp HEATER fuse or open in Blue wire between A/C cooling fan relay and fuse.
GROUND CIRCUIT TEST
Turn ignition off. Unplug connectors from cooling fan and A/C cooling fan relays. Check for continuity between ground and Black wire
terminal of relay connectors. If continuity is NOT present, repair Black ground wire.
FAN MOTOR TEST
Disconnect fan motor wire connector. Apply ground and battery voltage to motor connector. Fan should run. If fan does not run, replace
cooling fan motor.
COOLING FAN RELAY TEST
Unplug cooling fan relay connector. Apply battery voltage and ground to Yellow and Green/Red (Capri) or Black/Yellow and Green/Yellow
(Festiva) wire terminals of relay. Check continuity of relay across Yellow/Green (Capri) or Yellow/Red and Black (Festiva) wire connector
terminals. Ensure continuity is NOT present while relay is energized. When relay is de-energized, continuity should exist.
A/C COOLING FAN RELAY TEST
Unplug A/C relay connector. Apply battery voltage and ground to Blue and White (Capri) or Blue and Green (Festiva) wire terminals of relay.
Check continuity of relay across Blue and Red (Capri) or Yellow/Red and Black (Festiva) wire connector terminals. On Capri, ensure
continuity does NOT exist while relay is energized. On Festiva, ensure continuity exists while relay is energized. On Capri, when relay is de-
energized continuity should exist. On Festiva, when relay is de-energized, continuity should NOT exist.
COOLANT TEMPERATURE SWITCH TEST
Disconnect connector from coolant temperature switch located in thermostat housing. With coolant temperature less than 200°F (93°C) for
Capri or 194°F (90°C) for Festiva, check continuity between ground and coolant temperature switch. Ensure continuity exists. Start engine
and allow coolant temperature to reach 200°F (93°C) for Capri or 207°F (97°C) for Festiva. Check continuity between ground and coolant
temperature switch terminal. Continuity should NOT be present. If switch does not test as indicated, replace switch.
HARNESS & CIRCUIT CHECK TEST
Turn ignition off. Disconnect harness connectors of the following components: ECA, cooling fan motor, coolant temperature switch, cooling
fan relay and A/C cooling fan relay. Using an ohmmeter, check for continuity on the related harness leads of each connector. See Fig. 2
and
Fig. 3
.
WIRING DIAGRAMS
For further detail, see appropriate chassis wiring diagram in the WIRING DIAGRAMS article in the WIRING DIAGRAMS section.
Page 2 of 3 MITCHELL 1 ARTICLE - ENGINE COOLING FAN 1990-92 ENGINE COOLING Ford Motor Co. Engine Cooling Fans
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Fuel Pump Circuit
1. Turn ignition on. Connect jumper wire between fuel pump test connector terminals. See Fig. 1 or Fig. 2 . Turn ignition on to activate
fuel pump.
2. Listen for fuel pump sound. If there is no sound, check main fuse, inertia switch (located at left rear shock tower), fuel pump rel ay, fu el
pump and all electrical connections.

Fig. 1: Festiva Fuel System Electrical Schematic

Courtesy of FORD MOTOR CO.
(1)For 1991 fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. For 1992 fuel pressure specifications,
see FUEL PRESSURE SPECIFICATIONS
article.
Page 2 of 4 MITCHELL 1 ARTICLE - F - BASIC TESTING 1991-92 ENGINE PERFORMANCE Ford Motor Co. Basic Diagnostic Proced
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STG CIRCUIT PIN IDENTIFICATION
1. Turn ignition off. Install BOB, leaving ECA disconnected. Measure resistance between switch BOB test pin and ground. Cycle switch. I
f
resistance is greater than 10,000 ohms with switch open and less than 5 ohms when switch is closed, switch is okay; go to step 4). If
resistance is not greater than 10,000 ohms with switch open, or greater than 5 ohms when switch is closed, go to next step.
2. Turn ignition off. Disconnect switch. Connect ohmmeter between switch terminals on 2-pin switches, or between ground and switch
ECA terminal on multi-pin or one-pin switches. Cycle switch. If resistance is not greater than 10,000 ohms with switch open, or is
greater than 5 ohms when switch is closed, replace switch. If resistance is greater than 10,000 ohms with switch open and less than 5
ohms when switch is closed, switch is okay; go to next step.
3. Turn ignition off. Install BOB, leaving ECA disconnected. Measure resistance between BOB pin for suspected switch and BOB pins 26,
37, 57, and 60. If any measurement is less than 10,000, repair shorted wire in question. If all measurements are greater than 10,000
ohms, go to next step.
4. Turn ignition off. Install BOB, leaving ECA disconnected. Measure resistance between BOB pin for suspected switch and switch
connector. If resistance is greater than 5 ohms, repair wire in question. If sent here from SWITCH MONITOR TEST in QUICK TESTS,
replace ECA; otherwise, return to QUICK TESTS.
PINPOINT TEST STP - SWITCH TO POWER
STP CIRCUIT PIN IDENTIFICATION
1. Turn ignition off. Install BOB, leaving ECA disconnected. Turn ignition on. Cycle switch in question. Measure voltage between switch
BOB test pin and ground. If voltage changes from less than 4 volts to more than 10 volts, switch is okay. If sent here from SWITCH
MONITOR TEST in QUICK TESTS, replace ECA. If sent here from elsewhere in QUICK TESTS, return to QUICK TESTS. If voltage is
not as specified, go to next step.
2. Turn ignition on. Measure voltage at switch in question on wire to ECA. Cycle switch. If voltage changes from less than 4 volts to more
than 10 volts, repair wire from switch to ECA. If voltage does not change from less than 4 volts to more than 10 volts, go to next step.
3. Turn ignition on. Install BOB, leaving ECA disconnected. Measure resistance between BOB test pin for switch in question and ground
and between BOB test pin and BOB pins 37, 57, and 26. If resistance is greater than 10,000 ohms for all measurements, go to next step.
If resistance is not greater than 10,000 ohms for all measurements, repair wire to switch.
4. Disconnect switch. Measure resistance between switch terminals. Cycle switch. If resistance is less than 5 ohms with switch closed and
greater than 10,000 ohms with switch open, switch is okay. If sent here from SWITCH MONITOR TEST in QUICK TESTS, return to
QUICK TESTS. If sent here from elsewhere in QUICK TESTS, replace ECA. If resistance is not as specified, replace switch.
PINPOINT TEST VPWR - VEHICLE POWER
SwitchECA PinBOB PinWire Color
1.3L
ACS1Q10BLU/RED
BLMT1S23GRN
IDL1N18YEL/BLK
NGS/CES (1) 1V43BLU/WHT
PSPS1P19PNK
WOT2L27YEL
1.6L
BPS (2) 2L12LT GRN/BLK
IDL1E18GRN/ORG
NGS/CES (1) 1G8RED/BLU
PSPS1K19GRN/RED
(1)Manual transmission only.
(2)Turbo only.
NOTE:For 1.3L, blower m otor resistor m ust be disconnected, HEAT ER fuse m ust be rem oved, and blower
m otor switch m ust be in position "1" when testing ACS signal.
NOTE:Enter this test only when directed here from QUICK T EST S.
SwitchECA PinBOB PinWire Color
1.3L
ACS1Q10GRN
BOO1O2GRN/RED
DEF1T30BLK/BLU
Fan1R22YEL/RED
HLDT1U28WHT
VST1C5BLK/RED
1.6L
BOO1J3WHT/GRN
VST3B5BLK/RED
NOTE:Enter this test only when directed here from another PINPOINT T EST . T o prevent replacem ent of good
com ponents, note following non-EEC com ponents m ay be faulty: ignition switch, alternator, battery
cables, ground straps, or voltage regulator. T his test is intended to diagnose only ECA, wiring harness
circuits, and battery voltage.
Page 17 of 20 MITCHELL 1 ARTICLE - G - TESTS W/CODES 1991-92 ENGINE PERFORMANCE Ford Motor Co. Self-Diagnostics
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EBL
Electronic Back Light
ECM
Engine Control Module
ECT
Engine Coolant Temperature Sensor
EDIS
Electronic Distributorless Ignition System
EEC
Electronic Engine Control
EECS
Evaporative Emission Control System
EEPROM
Electronically Erasable PROM
EFE
Early Fuel Evaporation
EGO
Exhaust Gas Oxygen Sensor
EGR
Exhaust Gas Recirculation
ESA
Electronic Spark Advance
ESC
Electronic Spark Control
EST
Electronic Spark Timing
EVAP
Fuel Evaporative System
EVIC
Electronic Vehicle Information Center
EVP
EGR Valve Position Sensor
Exc.
Except
"F"
° F
Fahrenheit (Degrees)
F/B
Fuse Block
Fed.
Page 6 of 15 MITCHELL 1 ARTICLE - GENERAL INFORMATION Commonly Used Abbreviations
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Back To Article
GENERAL INFORMATION
T rouble Shooting - Basic Procedures
* PLEASE READ THIS FIRST *
ACCESSORIES & ELECTRICAL
CHARGING SYSTEM TROUBLE SHOOTING
BASIC CHARGING SYSTEM TROUBLE SHOOTING CHART NOTE:This is GENERAL inform ation. This article is not intended to be specific to any unique situation or
individual vehicle configuration. T he purpose of this T rouble Shooting inform ation is to provide a list
of com m on causes to problem sym ptom s. For m odel-specific T rouble Shooting, refer to SUBJECT ,
DIAGNOST IC, or T EST ING articles available in the section(s) you are accessing.
NOTE:This is GENERAL inform ation. This article is not intended to be specific to any unique situation or
individual vehicle configuration. T he purpose of this T rouble Shooting inform ation is to provide a list
of com m on causes to problem sym ptom s. For m odel-specific T rouble Shooting, refer to SUBJECT ,
DIAGNOST IC, or T EST ING articles available in the section(s) you are accessing.
NOTE:This is GENERAL inform ation. This article is not intended to be specific to any unique situation or
individual vehicle configuration. T he purpose of this T rouble Shooting inform ation is to provide a list
of com m on causes to problem sym ptom s. For m odel-specific T rouble Shooting, refer to SUBJECT ,
DIAGNOST IC, or T EST ING articles available in the section(s) you are accessing.
CONDITION & POSSIBLE CAUSECORRECTION
Vehicle Will Not Start
Dead batteryCheck battery cells, alternator
belt tension and alternator
output
Loose or corroded battery connectionsCheck all charging system
connections
Ignition circuit or switch malfunctionCheck and replace as necessary
Alternator Light Stays On With Engine Running
Loose or worn alternator drive beltCheck alternator drive tension
and condition, See Belt
Adjustment in TUNE-UP article
in the TUNE-UP section
Loose alternator wiring connectionsCheck all charging system
connections
Short in alternator light wiringSee Indicator Warning Lights in
STANDARD INSTRUMENTS
in the ACCESSORIES &
EQUIPMENT section
Defective alternator stator or diodesSee Bench Tests in
ALTERNATOR article
Defective regulatorSee Regulator Check in
ALTERNATOR article
Alternator Light Stays Off With Ignition Switch ON
Blown fuseSee WIRING DIAGRAMS
Defective alternatorSee Testing in ALTERNATOR
article
Defective indicator light bulb or socketSee Indicator Warning Lights in
STANDARD INSTRUMENTS
in the ACCESSORIES &
EQUIPMENT section
Alternator Light Stays OFF With Ignition Switch ON
Short in alternator wiringSee On-Vehicle Tests in
ALTERNATOR article
Defective rectifier bridgeSee Bench Tests in
ALTERNATOR article
Lights or Fuses Burn Out Frequently
Defective alternator wiringSee On-Vehicle Tests in
ALTERNATOR article
Defective regulatorSee Regulator Check in
ALTERNATOR article
Defective batteryCheck and replace as necessary
Ammeter Gauge Shows Discharge
Loose or worn drive beltCheck alternator drive belt
tension and condition. See Belt
Adjustment in TUNE-UP article
in the TUNE-UP section
Defective wiringCheck all wires and wire
Page 1 of 36 MITCHELL 1 ARTICLE - GENERAL INFORMATION Trouble Shooting - Basic Procedures
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AIR CONDITIONING & HEAT
AIR CONDITIONING TROUBLE SHOOTING
BASIC AIR CONDITIONING TROUBLE SHOOTING CHART
HEATER SYSTEM TROUBLE SHOOTING
BASIC HEATER SYSTEM TROUBLE SHOOTING CHART
Broken lead or loose soldered connectionsRepair wire or wire
connections as necessary
Solenoid Plunger Vibrates When Switch is Engaged
Weak batteryCharge or replace battery as
necessary
Solenoid contacts corrodedClean contacts or replace
solenoid
Faulty wiringCheck all wiring leading to
solenoid
Broken connections inside switch coverRepair connections or replace
solenoid
Open hold-in wiresolenoid
Low Current Draw
Worn brushes or weak brush springsReplace brushes or brush
springs as necessary
High Pitched Whine During Cranking Before Engine Fires but Engine Fires and Cranks Normally
Distance too great between starter pinion and flywheelAlign starter or check that
correct starter and flywheel are
being used
High Pitched Whine After Engine Fires With Key released. Engine Fires and Cranks Normally
Distance too small between starter pinion and flywheelFlywheel runout contributes to
the intermittent nature
WARNING:This is GENERAL inform ation. This article is not intended to be specific to any unique situation or
individual vehicle configuration. T he purpose of this T rouble Shooting inform ation is to provide a list
of com m on causes to problem sym ptom s. For m odel-specific T rouble Shooting, refer to SUBJECT ,
DIAGNOST IC, or T EST ING articles available in the section(s) you are accessing.
CONDITIONPOSSIBLE CAUSE
Compressor Not WorkingCompressor clutch circuit open.
.....Compressor clutch coil inoperative.
.....Poor clutch ground connection.
.....Fan belts loose.
.....Thermostatic switch inoperative.
.....Thermostatic switch not adjusted.
.....Ambient temperature switch open.
.....Superheat fuse blown.
Excessive Noise or VibrationMissing or loose mounting bolts.
.....Bad idler pulley bearings.
.....Fan belts not tightened correctly.
.....Compressor clutch contacting body.
.....Excessive system pressure.
.....Compressor oil level low.
.....Damaged clutch bearings.
.....Damaged reed valves.
.....Damaged compressor.
In su fficien t o r No Co o l in g; Co mp resso r
WorkingExpansion valve inoperative.
.....Heater control valve stuck open.
.....Low system pressure.
.....Blocked condenser fins.
.....Blocked evaporator fins.
.....Vacuum system leak.
.....Vacuum motors inoperative.
.....Control cables improperly adjusted.
.....Restricted air inlet.
.....Mode doors binding.
.....Blower motor inoperative.
.....Temperature above system capacity.
NOTE:This is GENERAL inform ation. This article is not intended to be specific to any unique situation or
individual vehicle configuration. T he purpose of this T rouble Shooting inform ation is to provide a list
of com m on causes to problem sym ptom s. For m odel-specific T rouble Shooting, refer to DIAGNOST IC,
or T EST ING articles available in the section(s) you are accessing.
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BRAKES
BRAKE SYSTEM TROUBLE SHOOTING
BRAKE SYSTEM TROUBLE SHOOTING CHART
CONDITIONPOSSIBLE CAUSE
Insufficient, Erratic, or No HeatLow Coolant Level
.....Incorrect thermostat.
.....Restricted coolant flow through core.
.....Heater hoses plugged.
.....Misadjusted control cable.
.....Sticking heater control valve.
.....Vacuum hose leaking.
.....Vacuum hose blocked.
.....Vacuum motors inoperative.
.....Blocked air inlet.
.....Inoperative heater blower motor.
.....Oil residue on heater core fins.
.....Dirt on heater core fins.
Too Much HeatImproperly adjusted cables.
.....Sticking heater control valve.
.....No vacuum to heater control valve.
.....Temperature door stuck open.
Air Flow Changes During AccelerationVacuum system leak.
.....Bad check valve or reservoir.
Air From Defroster At All TimesVacuum system leak.
.....Improperly adjusted control cables.
.....Inoperative vacuum motor.
Blower Does Not Operate CorrectlyBlown fuse.
.....Blower motor windings open.
.....Resistors burned out.
.....Motor ground connection loose.
.....Wiring harness connections loose.
.....Blower motor switch inoperative.
.....Blower relay inoperative.
.....Fan binding or foreign object in housing.
.....Fan blades broken or bent.
NOTE:This is GENERAL inform ation. This article is not intended to be specific to any unique situation or
individual vehicle configuration. T he purpose of this T rouble Shooting inform ation is to provide a list
of com m on causes to problem sym ptom s. For m odel-specific T rouble Shooting, refer to SUBJECT ,
DIAGNOST IC, or T EST ING articles available in the section(s) you are accessing.
CONDITION & POSSIBLE CAUSECORRECTION
Brakes Pull Left or Right
Incorrect tire pressureInflate tires to proper pressure
Front end out of alignmentSee WHEEL ALIGNMENT
Mismatched tiresCheck tires sizes
Restricted brake lines or hosesCheck hose routing
Loose or malfunctioning caliperSee DISC BRAKES or
BRAKE SYSTEM
Bent shoe or oily liningsSee DRUM BRAKES or
BRAKE SYSTEM
Malfunctioning rear brakesSee DRUM, DISC BRAKES
or BRAKE SYSTEM
Loose suspension partsSee SUSPENSION
Noises Without Brakes Applied
Front linings worn outReplace linings
Dust or oil on drums or rotorsSee DRUM, DISC BRAKES
or BRAKE SYSTEM
Noises With Brakes Applied
Insulator on outboard shoe damagedSee DISC BRAKES or
BRAKE SYSTEM
Incorrect pads or liningsReplace pads or linings
Brake Rough, Chatters or Pulsates
Excessive lateral runoutCheck rotor runout
Parallelism not to specificationsReface or replace rotor
Wheel bearings not adjustedSee SUSPENSION
Rear drums out-of-roundReface or replace drums
Disc pad reversed, steel against rotorRemove and reinstall pad
Excessive Pedal Effort
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TUNE-UP TROUBLE SHOOTING - GAS ENGINE VEHICLES
BASIC SPARK PLUG TROUBLE SHOOTING CHARTS
Faulty solenoid switch, switch connections or relayCheck all wiring between
relay and solenoid or replace
relay or solenoid as necessary
Broken lead or loose soldered connectionsRepair wire or wire
connections as necessary
Solenoid Plunger Vibrates When Switch is Engaged
Weak batteryCharge or replace battery as
necessary
Solenoid contacts corrodedClean contacts or replace
solenoid
Faulty wiringCheck all wiring leading to
solenoid
Broken connections inside switch coverRepair connections or replace
solenoid
Open hold-in wireReplace solenoid
Low Current Draw
Worn brushes or weakReplace brushes or brush
springs as necessary
High Pitched Whine During Cranking Before Engine Fires but Engine Fires and Cranks Normally
Distance too great between starter pinion and flywheelAlign starter or check that
correct starter and flywheel
are being used
High Pitched Whine After Engine Fires With Key released. Engine Fires and Cranks Normally
Distance too small between starter pinion and flywheelFlywheel runout contributes
to the intermittent nature
NOTE:This is GENERAL inform ation. This article is not intended to be specific to any unique situation or
individual vehicle configuration. T he purpose of this T rouble Shooting inform ation is to provide a list
of com m on causes to problem sym ptom s. For m odel-specific T rouble Shooting, refer to SUBJECT ,
DIAGNOST IC, or T EST ING articles available in the section(s) you are accessing.
CONDITION & POSSIBLE CAUSECORRECTION
Normal Spark Plug Condition
Light Tan or Gray depositsNo Action
Electrode not burned or fouledNo Action
Gap tolerance not changedNo Action
Cold Fouling or Carbon Deposits
Overrich air/fuel mixtureAdjust air/fuel mixture, see
ENGINE PERFORMANCE
section
Faulty chokeReplace choke assembly, see
ENGINE PERFORMANCE
section
Clogged air filterClean and/or replace air filter
Incorrect idle speed or dirty carburetorReset idle speed and/ or clean
carburetor
Faulty ignition wiresReplace ignition wiring
Prolonged operation at idleShut engine off during long
idle
Sticking valves or worn valve guide sealsCheck valve train
Wet Fouling or Oil Deposits
Worn rings and pistonsInstall new rings and pistons
Excessive cylinder wearRebore or replace block
Excessive valve guide clearanceWorn or loose bearing
Gap Bridged
Deposits in combustion chamber becoming fused to electrodeClean combustion chamber of
deposits
Blistered Electrode
Engine overheatingCheck cooling system
Wrong type of fuelReplace with correct fuel
Loose spark plugsRetighten spark plugs
Over-advanced ignition timingReset ignition timing see
ENGINE PERFORMANCE
Pre-Ignition or Melted Electrodes
Incorrect type of fuelReplace with correct fuel
Incorrect ignition timingReset ignition timing see
ENGINE PERFORMANCE
Burned valvesReplace valves
Engine OverheatingCheck cooling system
Wrong type of spark plug, too hotReplace with correct spark
Page 21 of 36 MITCHELL 1 ARTICLE - GENERAL INFORMATION Trouble Shooting - Basic Procedures
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Back To Article
GENERAL INFORMATION
T ROUBLE SHOOT ING
* PLEASE READ THIS FIRST *
ENGINE PERFORMANCE
TUNE-UP TROUBLE SHOOTING NOTE:T his article is generic in nature and all inform ation does not apply to all vehicles. For vehicle specific
inform ation, see the appropriate articles in the ENGINE PERFORMANCE category.
NOTE:T his article is generic in nature and all inform ation does not apply to all vehicles. For vehicle specific
inform ation, see the appropriate articles in the ENGINE PERFORMANCE category.
Problem & Possible CauseAction
Carbon Fouled Plugs
C l o gge d Air Fil t e rReplace Air Filter
Incorrect Idle SpeedReset Idle Speed
Faulty Ignition WiringReplace Ignition Wiring
Sticky Valves/Worn Valve SealCheck Valve Train
Fuel Injection OperationCheck Fuel Injection
Wet/Oil Fouled Plugs
Worn Rings/PistonsOverhaul/Replace Engine
Excessive Cylinder WearOverhaul/Replace Engine
Plug Gap Bridged
Combustion Chamber Carbon DepositsClean Combustion
Chamber
Blistered Electrode
Engine OverheatingCheck Cooling System
Loose Spark PlugsClean/Torque Plugs
Over-Advanced TimingReset Timing
Wrong Plug Heat RangeInstall Correct Plug
Melted Electrodes
Incorrect TimingReset Timing
Burned ValvesReplace Valves
Engine OverheatingCheck Cooling System
Wrong Plug Heat RangeInstall Correct Plug
Engine Won't Start
Loose ConnectionsCheck Connections
No PowerCheck Fuses/Battery
Loose/Worn Timing Belt/Chain/GearsCheck Belt/Chain/Gears
Engine Runs Rough
Leaky/Clogged Fuel InjectorsRepair Fuel Injectors
Leaky/Clogged Fuel LinesRepair Fuel Lines
Clogged Fuel FilterReplace Fuel Filter
Incorrect TimingReset Timing/Check
Advance
Faulty Plugs/WiresReplace Plugs/Wires
Uneven CompressionOverhaul/Replace Engine
Poor Acceleration
Incorrect Ignition TimingReset Timing
Leaky ValvesCheck Compression
Component Failure
Spark ArcingReplace Faulty Part
Defective Pick-Up CoilReplace Pick-Up Coil
Defective Ignition CoilReplace Ignition Coil
Defective Control UnitReplace Control Unit
Ignition Diagnosis By Scope Pattern
All Firing Lines Abnormally High
Retarded Ignition TimingReset Ignition Timing
Lean Air/Fuel MixtureAdjust Fuel Mixture
High Secondary ResistanceRepair Secondary
Ign it io n
All Firing Lines Abnormally Low
Rich Air/Fuel MixtureAdjust Air/Fuel Mixture
Arcing Coil WireReplace Coil Wire
Cracked CoilReplace Coil
Low Coil OutputReplace Coil
Low CompressionCheck/Repair Engine
Page 1 of 3 MITCHELL 1 ARTICLE - GENERAL INFORMATION TROUBLE SHOOTING
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FUEL INJECTION TROUBLE SHOOTING
Se ve r a l High F ir in g Lin e s
Fuel Mixture UnbalancedCheck Fuel System
EGR Valve Stuck OpenClean/Replace EGR
Valve
High Plug Wire ResistanceReplace Plug Wire
Cracked/Broken PlugsReplace Plugs
Intake Vacuum LeakRepair Leak
Several Low Firing Lines
Fuel Mixture UnbalancedAdjust Fuel Mixture
Plug Wires ArcingReplace Plug Wires
Cracked Coil ArcingReplace Coil
Uneven CompressionCheck/Repair Engine
Faulty Spark PlugsReplace Plugs
Cylinders Not Firing
Cracked Distributor CapReplace Cap
Shorted Plug WiresReplace Plug Wires
Mechanical Engine FaultCheck/Repair Engine
Spark Plugs FouledReplace Plugs
Carbon Track in Distributor CapReplace Cap
Hard Starting
Defective Ignition Coil(s)Replace Coil(s)
Fouled Spark PlugsReplace Plugs
Incorrect TimingReset Ignition Timing
NOTE:T his article is generic in nature and all inform ation does not apply to all vehicles. For vehicle specific
inform ation, see the appropriate articles in the ENGINE PERFORMANCE category.
Problem & Possible CauseAction
Cold Start Valve InoperativeTest Cold Start Valve
Poor Vacuum/Electrical ConnectionRepair Connections
Contaminated FuelTest Fuel for Water/Alcohol
Bad Fuel Pump Relay/CircuitTest Relay/Wiring
Battery Voltage LowCharge/Test Battery
Low Fuel PressureTest Press. Regulator/Pump
No Distributor Reference PulseRepair Ignition System
Coolant Temp. Sensor DefectiveTest Temp. Sensor/Circuit
No Power To InjectorsCheck Injector Fuse/Relay
Hard Starting
Defective Idle Air Control (IAC)Test IAC and Circuit
EGR Valve OpenTest EGR Valve/Control
Circuit
Restricted Fuel LinesInspect/Replace Fuel Lines
Poor MAP Sensor SignalTest MAP Sensor/Circuit
Engine Stalls During Parking ManeuverCheck P.S. Press. Switch
Rough Idle
Dirty Fuel InjectorsClean/Replace Injectors
Poor MAP Sensor SignalTest MAP Sensor/Circuit
Intermittent Fuel Injector OperationCheck Harness Connectors
Erratic Vehicle Speed Sensor InputsHarness Too Close to Plug
Wires
Poor O2 Sensor SignalTest O2 Sensor/Circuit
Faulty PCV SystemCheck PCV Valve and
Hoses
Poor Acceleration
Weak Fuel PumpReplace Fuel Pump
Dirty Fuel InjectorsClean/Replace Injectors
Excessive Intake Valve DepositsClean Intake System
Poor High Speed Operation
Low Fuel Pump VolumeFaulty Fuel Pump/Filter
Poor MAP Sensor SignalTest Speed Sensor/Circuit
Acceleration Ping/Knock
Faulty EGR SystemCheck EGR Valve and
Hoses
Poor Knock Sensor SignalTest Knock Sensor/Circuit
Poor Baro Sensor SignalTest Baro Sensor/Circuit
Improper Ignition TimingAdjust Timing
Engine OverheatingCheck Cooling System
Poor Quality FuelUse Different Fuel
Carbon Build-UpDecarbon Engine
Page 2 of 3 MITCHELL 1 ARTICLE - GENERAL INFORMATION TROUBLE SHOOTING
3/10/2009 http://www.eautorepair.net/app/PrintItems.asp?S0=2097152&S1=0&SG=%7B9B990D68%2D660A%2D45E9%2D8F46%2DE
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