Engine - Spark Knock When Under Heavy Load
Article No.93-5-6
March 3, 1993
^ EMISSION TEST FAILURE - 4.6L - NOT ABLE TO STABILIZE 2300-2800 RPM RANGE - TOWN CARS BUILT 9/1/90 THROUGH 8/31/91 AND CROWN VICTORIA/GRAND MARQUIS BUILT 1/2/91 THROUGH 2/28/92
^ SPARK KNOCK - 4.6L - TOWN CARS BUILT 9/1/90 THROUGH 8/31/91 AND CROWN VICTORIA/GRAND MARQUIS BUILT 1/2/91 THROUGH 2/28/92
FORD:
1992 CROWN VICTORIA
LINCOLN-MERCURY:
1991 TOWN CAR
1992 GRAND MARQUIS
This TSB article is being republished in its entirety to address Automobile Emission Testing Concerns.
CALIBRATION:
2-18A-R00, 2-18A-R10, 2-18B-R00, 2-18B-R10, 2-18P-R10, 1-18D-R00
WARNING:
THIS MODIFICATION IS AUTHORIZED ONLY FOR THE LISTED ENGINE. PERFORMING THIS MODIFICATION ON OTHER ENGINE CALIBRATIONS IS UNAUTHORIZED AND COULD CREATE LIABILITY UNDER APPLICABLE FEDERAL OR LOCAL LAWS.
ISSUE:
Spark knock may be experienced under heavy load. The detonation is more noticeable while the engine is under load, such as when the vehicle is driven at speed of 35 mph (56km/h) or higher in third or fourth gear, prior to downshifts during acceleration. Also, during Automobile Emission Testing (A.E.T.) some engines may experience difficulty maintaining engine speed in the 2300-2800 RPM range and consequently fail the A.E.T. Tests. These conditions may be caused by the operating strategy of the PCM Module.
ACTION:
Confirm the spark knock or failed emission test and, if necessary, install a new PCM Module. Refer to the following procedure for service details.
A.E.T. TEST CONCERNS
1. Verify the affected engine calibration(s). They are: 2-18A-R00, 2-18A-R10, 2-18B-R00 and 2-18B-R10.
2. Confirm vehicle failed emission test because of inability to stabilize 2300-2800 range R.P.M.
3. Remove and replace existing PCM Module. Refer to the Parts Block for correct parts usage.
SPARK KNOCK CONCERNS
1. Make sure that the customer is using fuel of the recommended octane requirement.
2. With the engine warmed to normal operating temperature, road test the vehicle to confirm the spark knock.
3. After detonation has been confirmed, check the coolant level mixture at the reservoir bottle. Refer to the Engine Cooling Section in the appropriate Car Service Manual for coolant information and cooling system fill procedure.
4. Check the engine coolant thermostat and ensure it is operating properly. Replace it if necessary. If all diagnostic checks have been performed and serviced as required and the condition still persists, proceed to Step 5.
5. Remove the octane adjust shorting bar which is located in the -12A581- wiring harness. Refer to the pertinent Volume "H" Manual for the procedure.
NOTE:
REMOVAL OF THE OCTANE ADJUST SHORTING BAR IS EQUIVALENT TO 30 SPARK RETARDATION.
6. Road test the vehicle. If spark knock is present, proceed to Step 7.
7. Remove the PCM Module and replace it with a new service module. Refer to the Parts Block for correct parts usage. Replacement PCM Module part numbers are concurrent with engine calibration numbers.
8. Road test vehicle. Confirm that the spark knock has been eliminated.
NOTE:
OPTIMUM ENGINE PERFORMANCE AND FUEL ECONOMY IS DEPENDENT ON MAXIMIZING SPARK ADVANCE WITHOUT DEVELOPING DETONATION. IN SOME CASES THE OCTANE ADJUST SHORTING BAR CAN BE USED WITH THE SERVICE REPLACEMENT PCM MODULE FOR MORE ENHANCED DRIVEABILITY.
9. If after performing Steps 5 through 8 the detonation concern is still objectionable, call the Romeo Engine Plant at 1-800-833-4503 for further assistance.
Obtain an Authorized Modifications Decal and list the date, dealer number, and summary of alterations performed. Select a prominent place adjacent to the Vehicle Emission Control Information Decal suitable for installing the Authorized Modifications Decal. Clean the area, install the decal, and cover it with a clear plastic decal shield.
OTHER APPLICABLE ARTICLES: NONE
SUPERSEDES: 92-9-3
WARRANTY STATUS:
Eligible Under Bumper To Bumper And Emissions Warranty Coverage
DEALER CODING
BASIC PART NO. CONDITION CODE
12A650 08
OASIS CODES:
615000, 615500, 623000