heating FORD FESTIVA 1991 User Guide

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
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The voltage controlled driver inside the computer operates much like a simple switch because it does not need to worry about limiting current
flow. Recall, this driver typically requires injector circuits with a total leg resistance of 12 or more ohms.
The driver is either ON, closing/completing the circuit (eliminating the voltage-drop), or OFF, opening the circuit (causing a total voltage
drop).
Some manufacturers call it a "saturated switch" driver. This is because when switched ON, the driver allows the magnetic field in the injector
to build to saturation. This is the same "saturation" property that you are familiar with for an ignition coil.
There are two ways "high" resistance can be built into an injector circuit to limit current flow. One method uses an external solenoid resistor
and a low resistance injector, while the other uses a high resistance injector without the solenoid resistor. See the left side of Fig. Fig. 1
.
In terms of injection opening time, the external resistor voltage controlled circuit is somewhat faster than the voltage controlled high resistance
injector circuit. The trend, however, seems to be moving toward use of this latter type of circuit due to its lower cost and reliability. The ECU
can compensate for slower opening times by increasing injector pulse width accordingly.

Fig. 1: Injector Driver Types
- Current and Voltage
CURRENT CONTROLLED CIRCUIT ("PEAK & HOLD")
The current controlled driver inside the computer is more complex than a voltage controlled driver because as the name implies, it has to limit
current flow in addition to its ON-OFF switching function. Recall, this driver typically requires injector circuits with a total leg resistance of
less than 12 ohms.
Once the driver is turned ON, it will not limit current flow until enough time has passed for the injector pintle to open. This period is preset by
the particular manufacturer/system based on the amount of current flow needed to open their injector. This is typically between two and six
amps. Some manufacturers refer to this as the "peak" time, referring to the fact that current flow is allowed to "peak" (to open the injector).
Once the injector pintle is open, the amp flow is considerably reduced for the rest of the pulse duration to protect the injector from
overheating. This is okay because very little amperage is needed to hold the injector open, typically in the area of one amp or less. Some
manufacturers refer to this as the "hold" time, meaning that just enough current is allowed through the circuit to "hold" the already-open
injector open.
There are a couple methods of reducing the current. The most common trims back the available voltage for the circuit, similar to turning down
a light at home with a dimmer.
The other method involves repeatedly cycling the circuit ON-OFF. It does this so fast that the magnetic field never collapses and the pintle
stays open, but the current is still significantly reduced. See the right side of Fig. Fig. 1
for an illustration.
The advantage to the current controlled driver circuit is the short time period from when the driver transistor goes ON to when the injector
actually opens. This is a function of the speed with which current flow reaches its peak due to the low circuit resistance. Also, the injector
closes faster when the driver turns OFF because of the lower holding current.
THE TWO WAYS INJECTOR CIRCUITS ARE WIRED
NOTE:Never apply battery voltage directly across a low resistance injector. T his will cause injector dam age
from solenoid coil overheating.
NOTE:Never apply battery voltage directly across a low resistance injector. T his will cause injector dam age
from solenoid coil overheating.
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1991-92 AIR CONDIT IONING & HEAT ING
A/C System General Servicing
HANDLING/SAFETY PRECAUTIONS
1. Always work in a well-ventilated, clean area. Refrigerant R-134a is colorless and is invisible as a gas. Refrigerant (R-12 or R-134a) is
heavier than oxygen and will displace oxygen in a confined area. Avoid breathing refrigerant vapors. Exposure may irritate eyes, nose
and throat.
2. The system's high pressure can cause severe injury to eyes and skin if a hose were to burst. Always wear eye protection when working
around A/C system and refrigerant. If necessary, wear rubber gloves or other protective clothing.
3. Refrigerant evaporates quickly when exposed to atmosphere, freezing anything it contacts. If liquid refrigerant contacts eyes or skin, DO
NOT rub eyes or skin. Immediately flush affected area with cool water for 15 minutes and consult a doctor or hospital.
4. Never use R-134a in combination with compressed air for leak testing. Pressurized R-134a in the presence of oxygen (air concentrations
greater than 60% by volume) may form a combustible mixture. DO NOT introduce compressed air into R-134a containers (full or
empty), A/C system components or service equipment.
5. DO NOT expose A/C system components to high temperatures, steam cleaning for example, as excessive heat will cause
refrigerant/system pressure to increase. Never expose refrigerant directly to open flame. If refrigerant needs to be warmed, place bottom
of refrigerant tank in warm water. Water temperature MUST NOT exceed 125°F (52°C).
6. Use care when handling refrigerant containers. DO NOT drop, strike, puncture or incinerate containers. Use Department Of
Transportation (DOT) approved, DOT 4BW or DOT 4BA, refrigerant containers.
7. Never overfill refrigerant containers. The safe filling level of a refrigerant container MUST NOT exceed 60% of the container's gross
weight rating. Store refrigerant containers at temperature less than 125°F (52°C).
8. R-12 refrigerant (Freon) will be sold and stored in White containers, while R-134a refrigerant will be sold and stored in 30- or 50-
pound Light Blue containers.
9. R-12 and R-134a refrigerants must never be mixed, as their desiccants and lubricants are not compatible. If the refrigerants are mixed,
system cross-contamination or A/C system component failure may occur. Always use separate servicing and refrigerant
recovery/recycling equipment.
10. Follow equipment manufacturer instructions of all service equipment to be used. The Material Safety Data Sheet (MSDS), provided by
refrigerant manufacturer/suppliers, contains valuable information regarding the safe handling of R-12 or R-134a refrigerants.
IDENTIFYING R-134A SYSTEMS & COMPONENTS
To prevent refrigerant cross-contamination, use following methods to identify R-134a based systems and components.
Fittings & "O" Rings
All R-134a based A/C systems use 1/2" - 16 ACME threaded fittings (identifiable by square threads) and quick-connect service couplings. See
Fig. 1
. Besides the use of these fittings, most manufacturers will use Green colored "O" rings in R-134a systems. CAUT ION: When discharging air conditioning system , use only approved refrigerant recovery/recycling
equipm ent. Make every attem pt to avoid discharging refrigerant into the atm osphere.
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Fig. 1: Identifying R
-134a Fittings & Quick Connect Service Couplings
Courtesy of AUDI OF AMERICA, INC.
Underhood A/C Specification Labels
Most R-134a based systems will be identified through the use of Green or Light Blue underhood labels, or with R-134a refrigerant clearly
printed on labels. See Fig. 2 . Some manufacturers will identify R-12 based systems with White, Red, Silver or Gold underhood labels. Before
servicing an A/C system, always determine which refrigerant is being used.
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Fig. 2: Underhood A/C Specification Labels (Typical)

Courtesy of NISSAN MOTOR CO., U.S.A.
Other Means Of Identification
Refrigerant R-134a, when viewed through a sight glass, may have a "milky" appearance due to the mixture of refrigerant and lubricating oil. As
the refrigerant and oil DO NOT exhibit a "clear" sight glass on a properly charged A/C system, R-134a systems have no sight glass.
Audi, Mercedes-Benz and Volkswagen use Green bands/labels on condenser, refrigerant lines, receiver-drier and expansion valve. Lexus A/C
system hoses and line connectors have a groove, a White line and "R-134a" marked on them. See Fig. 3
.

Fig. 3: Identifying R
-134a Hose & Line Connectors (Lexus)
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
REFRIGERANT OILS
Refrigerant R-12 based systems use mineral oil, while R-134a systems use synthetic/Polyalkylene Glycol (PAG) oils. Using a mineral oil based
lubricant with R-134a will result in A/C compressor failure due to lack of proper lubrication.
Use ONLY specified oil for the appropriate system and A/C compressor. Always check the underhood A/C specification label or A/C
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compressor label before adding refrigerant oil to A/C compressor/system. See Fig. 2 . The following R-134a refrigerant oils are currently
available.
Lexus
PAG Refrigerant Oil (ND-OIL 8) with 10P/10PA swashplate (piston) compressor. Synthetic Refrigerant Oil (ND-OIL 9) with through-va n e
(rotary vane) compressor.
Mercedes-Benz
PAG Refrigerant Oil (001 989 08 03).
Nissan
PAG Refrigerant Oil (KLH00-PAGR0) with rotary vane compressor. PAG Refrigerant Oil (KLH00-PAGS0) with piston (swashplate)
compressor.
Saab
PAG Refrigerant Oil (40 74 787).
SERVICE EQUIPMENT
Because R-134a is not interchangeable with R-12, separate sets of hoses, manifold gauge set and recovery/recycling equipment are required to
service vehicles. This is necessary to avoid cross-contaminating and damaging system.
All equipment used to service systems using R-134a must meet SAE standard J1991. The service hoses on the manifold gauge set must have
manual (turn wheel) or automatic back-flow valves at the service port connector ends. This will prevent refrigerant from being released into
the atmosphere.
For identification purposes, R-134a service hoses must have a Black stripe along its length and be clearly labeled SAE J2196/R-134a. The low
pressure test hose is Blue with a Black stripe. The high pressure test hose is Red with a Black stripe, and the center test hose is Yellow with a
Black stripe.
R-134a manifold gauge sets can be identified by one or all of the following.
Labeled FOR USE WITH R-134a on set
Labeled HFC-134 or R-134a on gauge face
Light Blue color on gauge face
In addition, pressure/temperature scales on R-134a gauge sets are different from R-12 manifold gauge sets.
SYSTEM SERVICE VALVES
SCHRADER-TYPE VALVES
Schrader valve is similar in construction and operation to a tire valve. When a test gauge hose with built-in valve core depressor is attached,
Schrader stem is pushed inward to the open position and allows system pressure to reach gauge.
If test hose does not have a built-in core depressor, an adapter must be used. Never attach hose or adapter to Schrader valve unless it is first
connected to manifold gauge set.
Refrigerant R-12 Schrader-type valve cores have TV5 thread size. Refrigerant R-134a Schrader-type valve cores use M6 (Metric) threads. R-
134a valve cores can be easily identified by use of "O" rings and external spring. See Fig. 1
.
SERVICE VALVE LOCATIONS
SERVICE VALVE LOCATIONS NOTE:Synthetic/PAG oils absorb m oisture very rapidly, 2.3-5.6% by weight, as com pared to a m ineral oil
absorption rate of .005% by weight.
NOTE:Refrigerant R-12 service hoses will ONLY be labeled SAE J2196.
NOTE:Although sim ilar in construction and operation to a tire valve, NEVER replace a Schrader-type valve
with a tire valve.
VehicleHighLow
Audi(14) (15)
Acura(2) (3)
BMW(4) (5)
Chrysler, Eagle & Mitsubishi
Colt, Mirage & Summit(10) (11)
Colt Vista & Summit Wagon(10) (11)
Diamante(1) (1)
Eclipse & Expo(10) (11)
Galant(10) (11)
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REFRIGERANT RECOVERY/RECYCLING
Refrigerant recovery/recycling equipment is used to remove refrigerant from vehicle's A/C system without polluting atmosphere. To remove
and recycle refrigerant, connect the recovery/recycling system and follow instructions provided with the system.
The removed refrigerant is filtered, dried and stored in a tank within the recovery/recycling system until it is ready to be pumped back into the
vehicle's A/C system. With refrigerant stored in the recovery/recycling system, A/C system can be opened without polluting atmosphere.
Montero(13) (13)
Pickup & Ram-50(10) (11)
Precis(12) (12)
Stealth & 3000GT(1) (1)
Daihatsu(4) (5)
Ford Motor Co.(4) (5)
General Motors & Geo(1) (1)
Honda(4) (5)
Hyundai
Elantra(4) (5)
Excel & Scoupe(12) (12)
Sonata(10) (11)
In fin it i(4) (5)
Isu zu(4) (5)
Jaguar(4) (5)
Lexus(4) (5)
Mazda
B2200 & B2600i(8) (8)
Miata(4) (5)
Navajo(6) (7)
All Others(1) (1)
Mercedes-Benz(4) (5)
Nissan(4) (5)
Porsche
1989-92 Carrera 911 2/4(8) (8)
Saab(8) (8)
Subaru
Legacy & Loyale(4) (5)
SVX(9) (9)
Suzuki(4) (5)
Toyota
Pickup & 4Runner(13) (13)
Supra(10) (11)
All Others(4) (5)
Volkswagen(4) (5)
Volvo(4) (5)
(1)Information is not available from manufacturer.
(2)On high pressure line (near receiver-drier on Legend; on receiver-drier on Vigor). Use High-Side Adapter (J-25498).
(3)On low pressure line (near right side of condenser on Legend).
(4)On high pressure (discharge) hose/line.
(5)On low pressure (suction) hose/line.
(6)On high pressure line, between compressor and condenser.
(7)On suction accumulator/drier.
(8)On low and high pressure hoses, behind compressor.
(9)On receiver/drier and low pressure hose (near compressor).
(10)On compressor high pressure (discharge) hose.
(11)On compressor low pressure (suction) port.
(12)On compressor discharge hose and accumulator.
(13)On compressor discharge and suction ports.
(14)Remove high pressure cut-out switch to expose high pressure service valve.
(15)Remove low pressure switch to expose low pressure service valve.
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NOTE:Separate sets of hoses, gauges and refrigerant recovery/recycling equipm ent MUST be used for R-12
and R-134a based system s. DO NOT m ix R-12 and R-134a refrigerants, as their refrigerant oils and
desiccants are NOT com patible. On system s with R-134a refrigerant, use Polyalkylene Glycol (PAG)
wax-free refrigerant oil.
Copyr ight 2009 Mitchell Repair Information Company, LLC. All Rights Reserved.
Article GUID: A00039025
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1991 AIR CONDIT IONING & HEAT
MANUAL A/C
A/C SYSTEM SPECIFICATIONS
SPECIFICATIONS
DESCRIPTION
This A/C-heater system is fully integrated to provide cooling, heating and ventilation with either fresh or recirculated air. A/C system is
expansion valve type. Interior air temperature is controlled by cycling the compressor on and off at different rates. A/C compressor is protected
by a low pressure switch, which stops compressor operation when refrigerant pressure is too low. Compressor operation is cut when throttle is
wide open to improve driveability.
The primary system components are compressor, receiver-drier, evaporator, low pressure switch, thermostatic switch, thermostatic expansion
valve, A/C control module, refrigerant lines and air ducts. See Fig. 1
and Fig. 2 . The heater core is continuously supplied with coolant. To
control temperature, air goes through and/or around heater core by way of temperature blend door.

Fig. 1: Identifying A/C System Components

Courtesy of FORD MOTOR CO. CAUT ION: When discharging air conditioning system , use only approved refrigerant recovery/recycling
equipm ent. Make every attem pt to avoid discharging refrigerant into the atm osphere.
ApplicationSpecification
Compressor TypeNippondenso 10-Cylinder
Refrigerant (R-12) Capacity25 ozs.
System Oil Capacity10 ozs.
Compressor Belt Deflection
New9/32-11/32" (8-9 mm)
Used11/32-7/16" (9-11 mm)
System Operating Pressure (1)
Low Side19-25 psi (1.3-1.7 kg/cm2 )
High Side199-220 psi (13.9-15.4
kg/cm
2 )
(1)When measured at 79°F (26°C).
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1. Inspect wiring and components for shorts, corrosion, overheating, loose connections, or any other damage. Check 10-amp METER fu se.
Disconnect downshift solenoid.
2. With key off, voltage measured at Black/Blue wire should be zero volts. With key on and accelerator pedal fully depressed, voltage
should be greater than 10 volts. If Black/Blue wire is okay, remove downshift solenoid.
3. Apply battery voltage to downshift solenoid connector and ground case. Control rod should move freely when solenoid case is
grounded. If control rod does not move freely, replace downshift solenoid.
VACUUM DIAPHRAGM ROD
If transaxle shift points are incorrect, check for a defective vacuum diaphragm and replace if necessary. If diaphragm is operating correctly,
check length of diaprhagm rod using Vacuum Diaphragm Rod Gauge (T87C-77000-A). Measure dimension "N." See Fig. 5
. Select proper
length diaphragm rod. See VACUUM DIAPHRAGM ROD SELECTION
table.
VACUUM DIAPHRAGM ROD SELECTION

Fig. 5: Adjusting Vacuum Diaphragm Rod Length

Courtesy of MAZDA MOTORS CORP.
Dimension "N" In. (mm)Rod Length In. (mm)
Below 1.000 (25.4)1.16 (29.5)
1.000-1.020 (25.4-25.9)1.18 (30.0)
1.020-1.039 (25.9-26.4)1.20 (30.5)
1.039-1.059 (26.4-26.9)1.22 (31.0)
Over 1.059 (26.9)1.24 (31.5)
Copyr ight 2009 Mitchell Repair Information Company, LLC. All Rights Reserved.
Article GUID: A00124558
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