1990 VOLKSWAGEN CORRADO Repair Manual

H - TESTS W/O CODES
Article Text (p. 4)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:45PM
cleaning additives. Prolonged use of poor quality fuel can
cause injector clogging and carbon build-up on intake system.
ENGINE MISFIRES OR HESITATES
CIS-E & CIS-E MOTRONIC
* Ensure injector spray patterns and volume are correct. Replace
faulty injectors.
* Check fuel system and control system pressure. Replace pressure
regulator if necessary.
* Check Oxygen (O2) sensor system operation.
* Check fuel lines and connections for leaks.
* Test coolant temperature sensor and wiring. Repair or replace
as required.
* Check airflow meter and throttle switch. Replace if faulty.
* Ensure vacuum hoses are not disconnected or damaged.
* Ensure electrical harness connectors and wires are not
broken or loose.
* Check cold start valve for leaking (engine warm).
DIGIFANT II
* Check airflow sensor flap and sensor resistance. Replace
if faulty.
* Inspect intake air components for leaking hoses, connections
or cracks. Repair as required.
* Test intake air preheating system. Replace faulty components
as required.
* Check fuel system and control system pressure. Replace pressure
regulator if necessary.
* Ensure vacuum hoses are not disconnected or damaged.
* Ensure electrical harness connectors and wires are not
broken or loose.
* Check cold start valve for leaking (engine warm).
* Check coolant temperature sensor operation.
* Check Oxygen (O2) sensor voltage output.
EXCESSIVE FAST IDLE
* Inspect accelerator pedal and cable for worn parts or binding.
* Test idle switch (if equipped).
* Test auxiliary air regulator and replace if necessary
(if equipped).
* Inspect throttle valve and adjust or replace as required.
* Check carbon canister solenoid valves (CIS-E Motronic).
* Test idle boost valve system operation (1.8L 8-valve engine
only). Replace faulty parts as necessary.
* Test coolant temperature sensor and wiring (Digifant II). Repair
or replace as required.
* Check throttle cable adjustment.
* Verify vacuum hose routing is correct.

H - TESTS W/O CODES
Article Text (p. 5)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:45PM
* Ensure there are no vacuum leaks.
* Check idle stabilizer operation (if equipped).
* Ensure fuel system pressure and volume are correct.
* Check auxiliary air by-pass regulator.
* Check cold start valve for leaking (engine warm).
ENGINE HESITATES ON ACCELERATION
* Inspect intake air components for leaking hoses
* Check injector spray pattern. Check for faulty injectors.
* Check cold start valve for leaking (engine warm).
* Check airflow sensor plate movement. Replace fuel distributor
as necessary.
* Check airflow sensor plate position. Adjust as necessary.
* Check fuel system and control system pressure. Replace pressure
regulator if necessary.
* Test airflow sensor plate potentiometer. Adjust or replace
as necessary.
* Perform system electrical checks.
* Check idle mixture CO adjustment. Adjust as necessary.
ENGINE LACKS POWER
* Test coolant temperature sensor and wiring. Repair or
replace as required.
* Check fuel system and control system pressure. Replace pressure
regulator if necessary.
* Check throttle cable adjustment.
* Check throttle switch. Adjust or replace as necessary.
* Check airflow sensor screen for damage or incorrect installation
(if equipped).
* Check ignition timing and knock sensor control (if equipped).
Adjust as necessary.
* Check EGR system for correct operation (if equipped).
* Ensure base timing is correct and timing advance system
is functional.
* Check transmission for correct downshift (auto. trans.)
* Check fuel tank filler tube for tampering of restrictor. If
tampering has occurred, check catalytic converter for lead
contamination and exhaust system restriction.
* Check for use of poor quality fuel containing insufficient
cleaning additives. Prolonged use of poor quality fuel can
cause injector clogging and carbon build-up on intake system.
* Inspect intake air element, housing, and preheating system.
* Check airflow sensor plate movement. Replace if necessary.
POOR FUEL MILEAGE
* Ensure idle speed, base timing and timing advance are
set to specifications.
* Check cold start valve for leaking (engine warm).

H - TESTS W/O CODES
Article Text (p. 6)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:45PM
* Check fuel system and control system pressure. Replace
pressure regulator if necessary.
* Check thermo time switch operation.
* Check airflow sensor voltage output.
* Check air induction system for leaks.
* Check fuel injector operation.
* Check coolant temperature sensor operation.
* Check Oxygen (O2) sensor operation.
ENGINE DIESELING
CIS-E & CIS-E MOTRONIC
* Ensure ignition timing and timing advance are set to
specifications.
* Check for engine overheating.
* Check cold start valve for leaking (engine warm).
* Check for leaking injectors.
* Check airflow sensor plate/control plunger rest position.
Adjust as necessary.
* Check carbon canister solenoid valve.
* Verify no leaks in exhaust system.
FAILED EMISSIONS TEST
* Test lambda control system. Replace if faulty.
* Check air/fuel mixture. Adjust if necessary.
* Ensure air intake system is not restricted.
* Ensure engine is at normal operating temperature.
* Ensure fuel system pressure is correct.
* Check cold start valve for leaking (engine warm).
* Check thermo time switch operation.
* Verify base timing is correct.
* Check for correct PCV valve operation.
* Check crankcase for gasoline contamination.
* Check idle stabilizer operation.
* Check EGR system for correct operation (if equipped).
* Check vapor recovery system operation.
* Check operation of coolant temperature sensor.
* Check fuel tank filler tube for tampering of restrictor.
If tampering has occurred, check catalytic converter for
lead contamination and exhaust system restriction.
* Check for use of poor quality fuel containing insufficient
cleaning additives. Prolonged use of poor quality fuel can
cause injector clogging and carbon build-up on intake system.
INTERMITTENT PROBLEM DIAGNOSIS
Intermittent fault testing requires duplicating circuit or
component failure to identify the problem. If necessary, monitor
voltage or resistance values using a DVOM while attempting to

H - TESTS W/O CODES
Article Text (p. 7)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:45PM
reproduce conditions causing intermittent fault.
A status change on DVOM indicates a fault has been located.
When monitoring voltage, ensure ignition switch is in ON position or
engine is running. Ensure ignition switch is in OFF position or
negative battery cable is disconnected when monitoring circuit
resistance.
TEST PROCEDURES
INTERMITTENT SIMULATION
To reproduce the conditions creating an intermittent fault,
use the following methods:
* Lightly vibrate component.
* Heat component.
* Wiggle or bend wiring harness.
* Spray component with water.
* Remove/apply vacuum source.
END OF ARTICLE

HEATER SYSTEM
Article Text
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:45PM
ARTICLE BEGINNING
1990 HEATER SYSTEMS
Volkswagen
Cabriolet, Corrado, Fox, Golf GL, GTI, Jetta,
Jetta GLi, Vanagon
WARNING: To avoid accidental air bag deployment, see AIR BAG
DEACTIVATION SERVICING PRECAUTIONS in this article.
DESCRIPTION
The heater is a water-valve type that combines heating,
defrosting and ventilation into one unit. Controls include fan control
knob and air distribution and temperature control levers. Blower fan
provides 3 speeds.
NOTE: Vanagon heater system information is not available from
manufacturer. For wiring diagram information, see WIRING
DIAGRAMS at end of this article.
OPERATION
When air distribution lever (upper lever) is in the center
stop position and lower temperature control lever is to the far left,
no air enters vehicle. As air distribution lever is moved to the left,
air is directed to floor vents. As distribution lever is moved to the
right, air is directed to defroster vents.
As heater lever (lower lever) is moved to the right, heater
turns on and heat output is increased. As the fan control knob is
turned to the right, the fan turns on and can be switched across its 3
speeds.
AIR BAG DEACTIVATION SERVICING PRECAUTIONS
WARNING: Some models are equipped with driver's side air bag
restraint system. Air bag-equipped vehicles have AIRBAG
stamped on the steering wheel horn pad. Air bag system
capacitor maintains a voltage charge sufficient to cause air
bag deployment for up to 20 MINUTES after ignition switch is
turned off and battery is disconnected.
DISABLING SYSTEM
Ensure ignition switch is OFF. Disconnect negative battery
cable and insulate terminal. Wait at least 20 MINUTES before
proceeding with repairs.
SYSTEM FUNCTIONAL CHECK

HEATER SYSTEM
Article Text (p. 2)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:45PM
When all service work is completed, reconnect negative
battery cable. Turn ignition on. Ensure the left turn indicator light
comes on for about 5 seconds and then goes out. If light does not come
on for about 5 seconds and then go out, air bag system needs to be
serviced.
TEMPERATURE CONTROL LEVER ADJUSTMENTS
Move temperature control lever to extreme left position.
Place heater control valve lever in closed position. Secure cable with
a clip.Fig. 1: Exploded View of Heater System (Cabriolet & Fox)
Courtesy of Volkswagen United States, Inc.

HEATER SYSTEM
Article Text (p. 3)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:45PMFig. 2: Exploded View of Heater System (Golf GL, GTI, Jetta &
Jetta GLi)
Courtesy of Volkswagen United States, Inc.

HEATER SYSTEM
Article Text (p. 4)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:45PMFig. 3: Exploded View of Heater System (Vanagon)
Courtesy of Volkswagen United States, Inc.
HEATER ASSEMBLY R & I
REMOVAL (CABRIOLET & FOX)
1) Drain coolant from radiator. Loosen clamps and remove
heater core hoses. Disconnect battery ground cable. Pull heater
control knobs off. Remove trim plate and underdash access panels.
2) Disconnect wiring from blower motor, and remove cable from
temperature control lever. Pry spring clamp off with screwdriver and
separate heater assembly halves. Remove heater core and blower motor.
INSTALLATION
To install, insert blower motor and heater core into right
half of housing. Position left half and install spring clips. To
complete installation, reverse removal procedure.
REMOVAL (GOLF GL, GTI, JETTA & JETTA GLI)
1) Disconnect negative battery cable. Drain coolant from
radiator. Remove steering wheel. Remove lower left instrument panel