Engine - Rough Idle

Classification:
EF&EC 93-007

Reference:
NTB93-117

Date:
August 5, 1993

Altima Idle Vibration

APPLIED VEHICLE:
1993 Altima (U13)

SERVICE INFORMATION
Some automatic transmission-equipped Altima's exhibit an idle vibration (rough idle) which can be felt through the steering wheel, seat, and floor. Such idle vibration (rough idle) may be most apparent when the engine is warm, the transmission is in "Drive", and the brake pedal is depressed while stopped in traffic. The idle adjustments indicated will eliminate this condition for many vehicles.

SERVICE PROCEDURE

1. Being with the following conditions:
^ Ignition Timing @ 20 +/- 2 degrees.
^ Engine temperature in "Normal" range.
^ Air Conditioning and Headlamps in the "off" position.
^ Shift lever in the "neutral" position and the engine idling.
^ Parking brake engaged.

2. Using CONSULT:
^ Select "A.A.C. VALVE ADJ" in "WORK SUPPORT" mode.
^ Touch "START"

OR, without CONSULT

^ Disconnect the Auxiliary Air Control (A.A.C.) valve harness connector.





3. Adjust the base idle speed at the AAC Valve to 687-700 RPM using a screwdriver (Figure 1).

4. Using CONSULT:
^ Touch "Back".

Or, without CONSULT:
^ Reconnect the A.A.C. valve harness.





5. Put the transmission in the "Drive" position and, using the mode screw, adjust the idle speed at the electronic control unit (E.C.U.) to 687 RPM (Figure 2)

NOTE:
The E.C.U. is accessed by removing the finisher on the center console, by the gas pedal.

Then, check for idle vibration. If an idle vibration is felt, readjust the idle speed to 700 RPM.

6. Confirm that the idle speed is 750 RPM or less in both the "Park" and "Neutral" position. If the idle speed is over 750 RPM, readjust the E.C.U. with the transmission in the "Drive" position and recheck, again.

NOTE 1:
Ensure that there is no booming noise from the exhaust heat shield plate while in "D" and "N" range.

NOTE 2:
If the E.C.U. screw is turned to select "Trouble Diagnosis Modes" the idle speed will require a reset, beginning at Step # 5.





WARRANTY INFORMATION