Engine - Vibrates at Idle Speed
83renault17E018
MARCH 1983
L42-M42
ENGINE - THROTTLE BODY FUEL
Attention: Workshop, Parts Department
INJECTION SYSTEM
INFORMATION
On some automatic transmission equipped L42-M42 models built prior to VIN 1AXXXXXXXXX139766, normal engine firing pulses may generate a vibration at idle speed when the transmission is in gear. The vibration can be eliminated by a moderate increase in engine idle speed. This is accomplished by installing a jumper harness in the ECU circuit to step-up the idle mode signal to the ECU. The step-up signal puts the ECU into a full load idle mode as if the A/C compressor were engaged.
NOTE: A revised ECU to improve engine idle is used on L42-M42 models with automatic transmission and throttle body fuel injection built after the VIN above.
Refer to the following procedure for ECU jumper harness installation procedures.
PROCEDURE
1. Disconnect the battery negative cable and remove the air cleaner.
2. On models with power steering, detach the power steering fluid reservoir and move the reservoir aside.
3. Locate and disconnect the black plastic 6-wire connectors of the ECU harness in the engine compartment.
NOTE: The 6-wire connectors are located below the radiator remote fill bracket near the dash panel.
4. Connect the ECU jumper harness between the two 6-wire connectors of the ECU harness.
CAUTION: Be sure all hamess connectors are securely attached and that the jumper hamess is routed away from hot or rotating engine components.
5. On models with power steering, install the power steering fluid reservoir.
6. Install the air cleaner and connect the battery negative cable.
7. Verify engine idle speed. Idle speed should now be about 1,000 rpm.
8. Mark the diagnostic connector bracket with a "J" in red paint to indicate that an ECU jumper harness has been installed. This will be an important reminder on future testing with the tester.
Effect of ECU Harness On Bendix Diagnostic Tester
The ECU jumper harness has the same effect on both A/C and non A/C models. It increases idle speed in either case by sending a step-up signal to the ECU that simulates full-time A/C operation.
On models with or without A/C, before checking the system with Electronic Diagnostic Tester, Tool MS 1700, always remove the jumper harness to avoid invalid tests.
PARTS
Description Quantity Part Number
HARNESS, ECU JUMPER 1 89 36 000 805
S.R.T. INFORMATION
Operation
Operation Description T.I.C. Number S.R.T.
CO. ECU JUMPER HARNESS - INSTALL 8-990 8999 0.4