Engine - Rough Idle Prior to Delivery
91mitsubishi07
NO. TSB-91-16-003
DATE July, 1991
MODEL 1991 3000GT, 1991 Mirage 1.5L
SUBJECT: ROUGH IDLE
PURPOSE
This Technical Service Bulletin describes how to correct rough idle by cleaning the spark plugs. On the 1991 Mirage with 1.5 liter engine, valve adjustment is also a part of the procedure.
AFFECTED VEHICLES
1991 3000GT and 1991 Mirage with 1.5 liter engine.
DESCRIPTION
Due to the short, frequent engine use associated with the transportation of new vehicles, some 1991 3000GT and Mirages (with 1.5 liter engines) may develop a rough idle prior to delivery to the customer. If a rough idle condition is present, it will be necessary to remove and clean the spark plugs and, on Mirages (1.5L), adjust the valve clearance.
To correct the rough idle condition, perform the steps shown below:
NOTE: Always wear safety goggles while operating any type of machinery.
1. Remove all spark plugs from the engine.
2. Inspect the end of each spark plug. If any are wet from engine flooding, clean them with carburetor cleaner or other suitable de-greaser. Using compressed air, dry each end thoroughly.
3. Insert each spark plug into a spark plug cleaning machine, rotating the plug to achieve full cleaning action. Refer to the following limitations on cleaning time:
Note: The cleaning time durations shown on page 2 of this TSB are applicable to NGK and Nippondenso plug cleaning machines. If using a different type of plug cleaner, follow the recommended plug cleaning times for that machine.
Plug Cleaning Machine:
NGK and NIPPONDENSO SPARK PLUG CLEANING MACHINES
a. Spark plugs for the Mirage must not be cleaned for more than 15 seconds.
b. Due to the use of platinum-tipped electrodes, spark plugs for the 3000GT must not be cleaned for more than 11 seconds.
OTHER MANUFACTURERS' SPARK PLUG CLEANING MACHINES
c. Mirage spark plugs may be cleaned at 100% of the recommended cleaning time for any standard plug cleaning machine.
d. Spark plugs for the 300OGT MUST NOT be cleaned for more than 75% of the recommended cleaning time for any standard plug cleaning machine.
4. Remove the spark plug from the plug cleaning machine. Use compressed air to eliminate all traces of cleaning compound from the spark plug.
Setting Spark Plug Gap:
5. Check the electrode gap of each spark plug. The gap for both the 1991 300OGT and Mirage is 1.1 mm.
6. If the gap is out of specification:
a. On the 3000GT, the spark plug must be replaced. The gap is not adjustable due to the platinum construction of the electrode tips. Refer to the illustration on page 3 of this TSB.
b. On the Mirage, reset the gap using a standard gapping tool. Refer to the illustration on page 3 of this TSB.
7. With spark plugs still removed, adjust the valve clearances on the Mirage (1.5 liter engine) to the following specifications:
Engine Coolant at 176 to 203 degrees F (80 to 95 degrees C)
Intake 0.15 mm (.006 in.)
Exhaust 0.25 mm (.010 in.)
8. Reinstall the spark plugs.
WARRANTY INFORMATION
Labor
Time Operation
Vehicle Operation Allowed Code
3000GT Remove and Install Spark Plugs 0.8 hrs. 16351010
3000GT Clean Spark Plugs 0.2 hrs. 16351000
TOTAL: 1.0 hrs.
Mirage (1.5L) Remove and Install Spark Plugs 0.3 hrs. 16351010
Mirage (1.5L) Clean Spark Plugs 0.2 hrs. 16351000
Mirage (1.5L) Adjust Valve Clearance 0.5 hrs. 11321500
TOTAL: 1.0 hrs. (1.5L)