Engine - Hesitation/Surge On Cruise/Light Acceleration
Article No.95-2-10
01/30/95
^ HESITATION/SURGE - CRUISE - DURING MILE PER GALLON (MPG) MODE OPERATION - NO DIAGNOSTIC TROUBLE CODES (DTC) STORED IN MEMORY - 4.9L ENGINE
^ HESITATION/SURGE - LIGHT ACCELERATION - MALFUNCTION INDICATOR LIGHT (MIL) "ON" - DIAGNOSTIC TROUBLE CODE (DTC) 179 STORED IN MEMORY - 4.9L ENGINE
^ HESITATION/SURGE - LIGHT ACCELERATION - MALFUNCTION INDICATOR LIGHT (MIL) "ON" - DIAGNOSTIC TROUBLE CODE (DTC) 179 STORED IN MEMORY - 4.9L ENGINE
LIGHT TRUCK:
1991-92 BRONCO
1991-94 ECONOLINE, F-150-350 SERIES
This TSB is being republished in its entirety to correct the PCM listing in Figure 7.
CALIBRATION:
1-51E-ROO, 1-51F-ROO, 1-51H-ROO, 1-51R-ROO, 1-51G-ROO, 1-52H-ROO, 1-52J-ROO, 1-52R-ROO, 1-52S-ROO, 1-52K-ROO, 1-52Q-ROO, 2-51E-ROO, 2-51F-ROO, 2-51H-ROO, 2-51R-ROO, 2-51G-ROO, 2-52H-ROO, 2-52J-ROO, 2-52R-ROO, 2-52S-ROO, 2-52K-ROO, 2-52Q-ROO, 2-52L-ROO, 3-51F-ROO, 3-51F-R10, 3-52J-R10
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:
Engine hesitation/surge during light acceleration may be caused by:
^ Incorrect service Exhaust Gas Recirculation (EGR) valve installed
^ Restricted exhaust system
^ Calibrations.
Engine hesitation/surge during steady cruise (greater than 50 mph (80 km/h) and no DTC'S) may be caused by:
^ The calibration of the MPG mode (only with calibrations 3-51F-ROO, 3-51F-R10, or 3-52J-R10).
ACTION:
Refer to the following procedures and figure charts for diagnosis and repair.
DIAGNOSIS AND REPAIR PROCEDURE
NOTE:
IF ONLY DTC 179 WAS SET AND NO HESITATION/SURGE CONDITION EXISTS, DO NOT REPLACE THE PCM. REFER TO THE POWERTRAIN CONTROL/EMISSIONS DIAGNOSIS (PC/ED) MANUAL, FOR THE APPROPRIATE PINPOINT TESTS AND SERVICE AS REQUIRED.
1. Verify the vehicle has the proper EGR valve installed. Refer to the charts to check which EGR valve is required. Replace the EGR valve with the proper service replacement EGR valve, if required (Figures 1 through 4).
NOTE:
PROPER DIAGNOSIS FOR A RESTRICTED EXHAUST SYSTEM IS ESSENTIAL BEFORE ANY COMPONENTS ARE REPLACED. REFER TO THE APPROPRIATE PC/ED SERVICE MANUAL FOR CATALYST AND EXHAUST SYSTEM DIAGNOSIS AND TEST PROCEDURES.
WARNING:
TO PREVENT SERIOUS BURNS, ALWAYS ALLOW AMPLE COOLING TIME AND WEAR PROTECTIVE GLOVES BEFORE WORKING WITH EXHAUST SYSTEM PARTS.
2. Visually inspect the entire exhaust system for any obvious signs of restriction. If any restriction is noted, service the fault. Refer to the appropriate year Econoline/F-Series/Bronco Service Manual, Group 9, Exhaust System, for service.
CAUTION:
THE H02S (HEATED OXYGEN SENSOR) ELECTRICAL CONNECTOR MUST BE DISCONNECTED TO AVOID EXCESSIVELY RICH AIR/FUEL MIXTURE DURING TESTING.
3. Disconnect the electrical connector from the Heated Oxygen Sensor (HO2S).
4. Remove and retain the HO2S from the catalyst inlet pipe.
5. Install Exhaust Back Pressure Gauge (D95L-6000-A) into the catalyst inlet pipe.
6. Disconnect and cap the vacuum hose to the Air Injection Reaction (AIR) Bypass Valve.
7. With the engine idling at normal operating temperature, observe the Exhaust System Backpressure reading of the gauge. The reading should not exceed 8.6 kPa (1.25 psi).
8. Increase engine speed to 3000 RPM and hold for 3 seconds, while observing the readings of the gauge. The readings should not exceed 20.7 kPa (3.00 psi).
9. If gauge readings at either engine speed are within specifications, and the hesitation/surge condition still exists, reinstall the HO2S (if required, apply a light coat of Loctite Nickel Anti-Seize PN 23508 to the threads of the sensor), reconnect the vacuum hose to the Air Injection Reaction (AIR) Bypass Valve, and replace the PCM. Refer to PCM replacement figure charts (Figures 5 through 8).
10. If gauge readings at either engine speed are not within specifications, a restricted exhaust system condition exists. Repeat Steps 7 through 9 by disconnecting individual exhaust system parts one at a time, starting at the back, until the faulty part is found. Replace only the faulty part. If the catalytic converter is found to be at fault, refer to the following Supplemental Diagnostic Instructions, also refer to Section 15A of the PC/ED to find the root cause of the failure.
11. Clear any DTC's falsely set during the exhaust system backpressure testing.
SUPPLEMENTAL DIAGNOSTIC PROCEDURES
If the catalytic converter is found to be the root cause of the symptom, the following areas should be checked:
1. Proper operation of the H02S. A defective H02S can give the following results in testing:
^ HO2S inoperative
^ HO2S circuit open or shorted
^ HO2S bias rich
^ HO2S bias lean or not grounded
^ HO2S slow to switch, from lean to rich
^ HO2S slow to switch, from rich to lean.
NOTE:
ANY OF THE ABOVE CONDITIONS CAN CAUSE ADDITIONAL HEAT THROUGH THE CATALYST. PERFORM THE SELF TEST KOEO AND KOER AS OUTLINED IN THE PC/ED MANUAL, SECTION 2A, FOR DIAGNOSTIC ROUTINES.
NOTE:
CHECK THE H02S GROUND CIRCUIT IF DTC'S 171, 172, 173, 179, 181, 182, 183, AND 565 ARE FOUND.
2. If the H02S circuit is operating properly, visually inspect the entire emissions system for proper operation. The following areas should be checked:
^ Ignition coil
^ Distributor cap
^ Distributor rotor
^ Spark plug(s) condition
^ Engine air cleaner (ACL) system
^ Intake or exhaust manifold leaks
^ Fuel injector(s) stuck open/shut
^ Wrong or contaminated fuel
^ Fuel pressure/leak down
^ Fuel contaminated engine oil
^ Poor system (power) ground
^ Engine not at normal operating temperature (faulty thermostat)
^ CANP system.
When performing the checks, also check the following areas:
^ All wiring harnesses and connectors for corrosion, insulation damage, burned, overheated, loose or broken conditions.
^ Vacuum hoses for proper routing and condition.
^ Spark plug wires properly routed and securely connected.
^ Proper operation of the engine cooling thermostat.
3. Improper ignition timing can cause additional heat through the catalyst. Perform the following tests and check ignition timing:
a. Disconnect the Spark Out (SPOUT) shorting bar.
b. With a timing light, check base timing. If base timing is not within the specifications listed on the emissions decal, adjust timing to specifications.
c. Reconnect the SPOUT shorting bar.
d. With a timing light, check the PCM operation of computed timing.
4. Misfiring spark plugs may allow an unburned air/fuel mixture to enter the catalyst and create higher than normal catalyst temperatures. Perform the following tests and check spark plugs:
^ Check secondary ignition with an engine analyzer for an ignition misfire.
5. High fuel pressure may allow a rich air/fuel mixture to enter the catalyst and create higher than normal catalyst temperatures. Perform the following tests and check fuel pressure:
a. Install fuel pressure gauge (T80L-9974-B).
b. Start and warm up the vehicle to normal operating temperature.
c. With the engine idling, check fuel pressure gauge readings. Typical gauge values will range from 43-49 psi (296.5-338 kPa).
d. Disconnect and cap the fuel pressure regulator vacuum hose.
e. Check fuel pressure gauge readings. Values should increase to a range of 52-58 psi (358.5-400 kPa).
NOTE:
FUEL PRESSURE GAUGE READINGS GREATER THAN THESE VALUES NEED TO BE CORRECTED. HOWEVER, THIS FAULT MAY NOT BE THE CAUSE OF THE SYMPTOMS.
f. Reconnect the fuel pressure regulator vacuum hose.
g. Shut engine off. Fuel pressure gauge values should hold within 5 psi (34.5 kPa) for 60 seconds. If the gauge values drop greater than 5 psi (34.5 kPa) in 60 seconds, refer to the PC/ED Manual and correct the leak down condition.
h. Remove fuel pressure gauge.
6. Partially open throttle plates may allow a rich air/fuel mixture to enter the catalyst during high vacuum decelerations and create higher than normal catalyst temperatures. Perform the following tests and check throttle body operation:
NOTE:
NON-OEM EQUIPMENT, IMPROPERLY INSTALLED, CAN INTERFERE WITH PROPER OPERATION OF THE THROTTLE BODY. THESE ITEMS MAY INCLUDE GOVERNORS, THROTTLE LINKAGES FOR POWER TAKE-OFF UNITS, ETC. THIS FAULT COULD BE THE CAUSE OF THE SYMPTOMS AND MUST BE SERVICED AS REQUIRED.
a. Visually inspect the throttle body and linkages for:
^ Binding or sticking throttle linkages
^ Binding or sticking speed control linkages
^ Vacuum hose restriction or interference
^ Electrical harness interference
^ Restrictive material within the Engine Air Cleaner (ACL).
7. Proper operation of the Air Injection Reaction (AIR) system. Visually inspect the AIR system for damaged or kinked hoses. Perform a function test on the following components:
^ AIR diverter solenoid
^ AIR bypass solenoid
^ AIR filter
^ Check valve
^ Silencer.
8. Proper operation of the Idle Air Control (IAC) system. Perform an idle speed mode test to verify proper operation of the IAC valve.
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.
The part number the Ford Dealership should use when ordering the Loctite Nickel Anti-Seize direct from Loctite's Cleveland, OH office is 23508.
The Ford Dealership should call 1-800-338-9000, 8 AM - 5 PM (EST), or FAX 1-800-548-7389 and ask for the Ford Anti-Seize Program PN 23508.
The Dealer should have a purchase order (or name of Dealer) as well as a ship to address. The charges are as follows:
Parts Block
OTHER APPLICABLE ARTICLES: NONE
SUPERSEDES: 94-20-15
WARRANTY STATUS:
Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage For 1992-94 Model Years, Basic Warranty Coverage For All Other Years - NOTE: Emission Warranty Coverage For MIL "On" And/Or EGA Valve Replacement
OPERATION DESCRIPTION TIME
950210A Perform EEC Self Test, 1.3 Hrs.
Re-Test, Verify Proper EGR
Installation, Perform
Exhaust System
Backpressure Test - All
Vehicles
950210B Replace EGR Valve - 0.3 Hr.
F-Series, Bronco
950210C Replace EGR Valve - 0.4 Hr.
Econoline
950210D Perform Converter 0.6 Hr.
Diagnosis - All Vehicles
950210E Replace PCM - 1991 0.3 Hr.
F-Series And Bronco,
1991-94 Econoline
95021OF Replace PCM - 1992-94 0.8 Hr.
F-Series, 1992 Bronco
DEALER CODING
BASIC PART NO. CONDITION CODE
1991 MODELS,
DRIVE 08
1992-94
MODELS,
RECAL 08
OASIS CODES:
206000, 610000, 610500, 611000, 611500, 612000, 612600, 698298