Fuel - Hesitate, Surge or Stop Running: Overview
91mitsubishi03
NO. TSB-91-11-003
DATE February, 1991
MODEL 1990 Mirage, 1990 Galant
SUBJECT:
GALANT 2.0L AND MIRAGE 1.5L COLD DRIVEABILITY
PURPOSE
Some 1990 Galant 2.0L and Mirage 1.5L models may hesitate, surge, or stop running during the first 60 seconds of cold engine operation. This condition usually occurs after tens of thousands of miles of operation and may possibly be caused by fuel deposits on the intake valves and partially clogged fuel injectors.
GENERAL INFORMATION
Some gasolines contain detergents and additives which may leave carbon-like deposits on the back side of the intake valves. These deposits accumulate gradually with mileage, and act as a sponge, absorbing gasoline during cold engine operation. This produces a lean mixture causing the engine to stop running, hesitate, or surge. After about 60 seconds as the intake valve and deposits warm up, the fuel vaporizes, thus minimizing the effects that deposits have on driveability conditions when warm.
This situation is aggravated when the fuel injectors become partially clogged.
The deposits may be removed from the intake valve by one of two means: (1) The intake manifold may be removed and the intake valve cleaned by using a commercially available walnut shell carbon blaster. (2) The intake valves may be removed from the cylinder head and the carbon deposits removed mechanically from the intake valve.
Whenever deposits are removed from the intake valve the fuel injectors should be cleaned using Mitsubishi Motors Diamond Car Care Fuel lnjector Cleaner, part number A991ZC1X01. This kit can only be ordered through Diamond Car Care Chemicals using the appropriate order form available through the parts system.
WARRANTY INFORMATION
Normal warranty procedures and coverage apply.
PRE-CHECKS
1. Check the MPI computer system for trouble codes. If codes are present, repair the problem area.
2. Inspect the air flow sensor, the air intake hose, the throttle body and the air intake plenum for oil deposits. If deposits exist, clean them.
3. Check the condition of the spark plugs. If they are covered with carbon, clean or replace them.
If during the pre-check you find that repairs are necessary, make them, and then verify whether the condition still exists.
DEPOSIT REMOVAL
Carbon Blaster Method:
1. Refer to the appropriate vehicle service manual for intake manifold removal procedures. Refer to the carbon blaster manufacturers' instructions for blaster operation.
WARNING: Wear safety goggles when operating any type of carbon blaster. The use of an OSHA approved dust filter/respirator is also recommended.
2. Reinstall the intake manifold and clean the fuel injectors.
Engine Disassembly Method:
1. Refer to the appropriate vehicle service manual for cylinder head removal procedures.
CAUTION: The engine must be cold when removing the cylinder head. If hot, the cylinder head may warp when removed.
2. Remove the intake valves. Remove the carbon from the intake valves.
WARNING: Wear safety goggles when removing carbon from the intake valves. The use of an OSHA approved dust filter/respirator is also recommended.
3. Reinstall the cylinder head and clean the fuel injectors.
FUEL INJECTOR CLEANING
Refer to the Mitsubishi Motors Technical Training Videotape number 36 for fuel injector cleaning instructions for use with the Mitsubishi Motors Diamond Car Care Fuel Injector Cleaner Kit.
Attached to this bulletin is a copy of the Mftsubishi Motors Diamond Car Care Fuel Injector Cleaner Kit Instructions.