Air/Fuel Mixture: Testing and Inspection
RETURNING ENGINE TO BASIC SETTINGSOVERVIEW
Ignition timing, idle speed, and oxygen sensor factor (Air/Fuel Mixture) are completely controlled by the Motronic Engine Control Module (ECM). These values CAN NOT BE ADJUSTED, only checked.
Returning the engine to basic settings allows the Motronic ECM to compensate for slight changes such as present engine condition, sensor component wear, environment and climate changes. The ECM will adapt to changing conditions and component input values then vary output signals as needed to obtain minimum emissions output. Returning engine to basic settings erases operating parameters the ECM has "learned" over time.
Once the "learned" parameters are erased, the ECM will "re-learn" and establish new operating parameters based on present sensor input signals and engine condition. There are NO adjustments which effect the actual air/fuel mixture, likewise NO adjustment for idle speed and the ignition distributor is equipped, with locating pins to prevent any movement.
Completeing this entire procedure once started is very important to both driveablity and exhaust emissions. Failure to complete or properly execute this procedure may result in a period of unstable idle along with increased exhaust emissions.
ON-BOARD DIAGNOSTICS
The first step in troubleshooting any Motronic system is to access the On Board Diagnostics and correct any faults stored in the Diagnostic Trouble Code Memory. YOU MUST ERASE the Diagnostic Trouble Code Memory before starting and after completion of this procedure, even if no codes are stored. Failure to do so will make checking procedure invalid.
For Diagnostic Trouble Code display and erasing procedures refer to:
^ Computers And Control Systems
^ Testing And Inspection
^ Procedures
^ On-board Diagnostics
NECESSARY EQUIPMENT
If the equipment necessary to accurately perform this work is not available, consider refering the job to a repair shop that has the required test equipment. With proper equipment these checks can be made quickly, accurately, at a reasonable cost.
REQUIRED PRE-CHECK CONDITIONS
1. Engine oil temperature must be at least 176°F (80°C) and radiator cooling fan has operated at least once.
2. All electrical consumers switched "OFF" (radiator cooling fan must not be running during checking).
3. A/C switched "OFF".
4. Throttle Position Sensor is functioning properly.
5. Idle stabilization system operating properly, the valve must vibrate or hum while the ignition is "ON".
6. The exhaust system must be free of leaks.
7. There can be NO intake manifold vacuum leaks.
8. The Heated Oxygen Sensor must be operating properly.
9. Throttle cable adjustment must be OK.
10. DTC memory must be cleared of stored trouble codes. If found, faults must be corrected. DTC memory MUST be erased before starting.
VEHICLE AND EQUIPMENT SET-UP
1. Vehicle in PARK or NEUTRAL with parking brake set.
2. Turn ignition switch "OFF".
3. Connect VW 1367 engine tester using VAG 1367/8 inductive pickup, or a suitable strobe timing light and tachometer may be used.
Underhood Component Location:
4. Remove cap from CO Tap Tube (#11 in image). Connect an EPA approved CO tester to the CO Tap Tube using VW special tool #6006-0019 high temperature silicone connecting hose, (or equivalent).
NOTE: Non-approved connecting hoses may dramatically alter your readings. Adaptor must be connected tightly to CO tap tube to prevent measuring errors.
5. Display and erase DTC memory, after display of code 0000 (DTC clear) leave ignition switch turned ON.
ENGINE BASIC SETTING INITIATING
1. Display and erase DTC memory, after display of code 0000 (DTC clear) leave ignition switch turned ON.
2. START engine and let IDLE (1300 rpm maximum) with throttle closed.
Data Link Connectors And Jumper Cable:
Jumper Wire To DLC Hookup:
3. With engine RUNNING, join WHITE jumper cable connector to WHITE DLC connector. If using jumper wire join connectors J1 and J2 together.
^ MIL in dash MUST light up.
^ IF NOT:
^ Check wires from DLC to the Motronic ECM for open.
^ Check jumper connections.
4. CONTINUE TEST ONLY WHEN:
^ Engine Coolant Temperature is OVER 176° F (80° C) or coolant fan has cycled at least once.
^ Engine has RUN 2 MINUTES or more at Closed Throttle Position.
5. Check closed throttle idle speed. Should be:
^ 840 ± 40 rpm (A/C OFF)
^ 870 ± 40 rpm (A/C ON)
6. Check CO content. Should be:
^ 0.3 - 1.2 vol. %
7. Check ignition timing. Should be:
^ Approx. 12° BTDC
NOTE: Coolant Fan MUST NOT BE RUNNING when the following test steps are started. If fan is running wait for fan cycle to end.
8. Disconnect WHITE jumper connector from WHITE DLC or separate jumper wire connectors J1 and J2 (reverse of step 3).
^ MIL will go OFF
Data Link Connectors And Jumper Wire:
9. With engine STILL RUNNING, join WHITE jumper cable connector to WHITE DLC connector. If using jumper wire join connectors J1 and J2 together.
10. After approx. 4 seconds disconnect WHITE jumper connector from WHITE DLC or separate jumper wire connectors J1 and J2.
^ MIL will go OFF, come ON for 2.5 seconds, go OFF.
^ This confirms display signal has been received.
^ MIL will then display (flash) trouble code.
^ Should be code 0000.
11. Turn ignition switch OFF, remove test equipment.
12. Test drive vehicle for at least 10 minutes (minimum). During test drive these requirements must be performed.
^ Engine coolant temperature must be over 176°F (80°C) for at least 3 minutes.
^ At engine speed over 4600 RPM, press accelerator pedal briefly all the way down.
^ In 4th gear, starting from approx. 30 mph accelerate for about 4 seconds with accelerator pedal at half throttle.
^ ECM will not reset properly unless ALL REQUIRED SENSOR SIGNALS have been generated during road test.
Motronic ECM Location:
IF SPECIFIED VALUES ARE NOT OBTAINED
^ With ignition switch OFF, disconnect Motronic Engine Control Module connector and re-connect.
^ Test drive car and check DTC memory again.
^ Repeat Returning Engine To Basic Settings procedure.