REPLACEMENT PAGE 1986 MANUAL DRIVEABILITY SECTION. Chevrolet Celebrity 1986

For 1990-2009 cars

# REPLACEMENT PAGE 1986 MANUAL DRIVEABILITY SECTION

This bulletin provides a replacement page 6E2-A-46 for the 1986 Celebrity Service Manual (ST-385-86).

The replacement page contains revised parameters for the setting of a Code 35.

Copy this new page and insert it in the appropriate manual.

CODE 35 IDLE SPEED ERROR 2.5L -A- SERIES FUEL INJECTION (TBI)

#### Circuit Description:

Code 35 will set, when the closed throttle engine speed is 100 rpm above or below the desired idle speed for 45 seconds. Review general description in Section "C".

Test Description: Step numbers refer to step numbers on diagnostic chart. ----------------

1.Continue with test, even if engine will not idle. If idle is to low, "Scan" will dispIay 80 or more counts, or steps. If idle is high, it will display "0" counts. Occasionally an erratic or unstable idle may occur. Engine speed may vary 200 rpm or more up and down. Disconnect IAC. If the condition is unchanged, the IAC is not at fault.

2. When the engine was stopped, the IAC Valve retracted (more air) to a Exed "Park" position for increased air flow and idle speed during the next engine start. A 'Scan" will display 100 or more counts.

3. Be sure to disconnect the IAC valve prior to this test. The test light will confirm the ECM signals by a steady or flashing light on all circuits.

4. There is a remote possibility that one of the CKTs is shorted to voltage, which would have been indicated by a steady light. Disconnect ECM and turn the Ign. on and probe terminals to check for this condition.

#### Diagnostic Aids:

A slow unstable idle may be caused by a system problem that cannot be overcome by the IAC. "Scan-counts will be above 60 counts, if too low, and "O" counts, if too high.

If idle is too high, stop engine. Ignition "ON". Ground diagnostic terminal. Wait a few seconds for IAC to seat, then, disconnect IAC. Start engine. If idle speed is above 800 + / - 50 rpm, locate and correct vacuum leak.

o System too lean (High Air/Fuel Ratio)

Idle speed may be too high or too low. Engine speed may vary up and down, disconnecting IAC does not help. May set Code 44. 'Scan" and/or Voltmeter will read an oxygen sensor output less than 300 mv (.3 volts). Check for low regulated fuel pressure or water in fuel. A lean exhaust, with an oxygen sensor output fixed above 800 mv (.8 volts), will be a contaminated sensor, usually silicone. This may also set a Code 45.

o System too rich (LowAir/FuelRatio)

Idle speed too low. "Scan" counts usually above 80. System obviously rich and may exhibit black smoke exhaust. 'Scan" tool and/or Voltmeter will read an oxygen sensor signal fixed above 800 mv (.8 volts). Check: - High fuel pressure - Injector leaking or sticking

o Throttle Body - Remove IAC and inspect bore for foreign material or evidence of IAC valve dragging the bore.

o Refer to Rough, Unstable, Incorrect Idle or Stalling in Symptoms in Section "B".

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.