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TSB 91-25-07 IAC Sludge; Poor Idle
Publication Date: DECEMBER 13, 1991

IF THE IMAGE ABOVE IS TOO SMALL TO READ, CLICK IT

FORD: 1983-87 EXP
1983-91 ESCORT
1984-90 MUSTANG, THUNDERBIRD
1986-90 TAURUS
1986-91 CROWN VICTORIA
1988-90 TEMPO
LINCOLN-MERCURY: 1983-85 LN7
1983-87 LYNX
1984-88 CAPRI
1984-90 COUGAR
1986-90 CONTINENTAL, MARK VII, SABLE
1986-91 GRAND MARQUIS, TOWN CAR
1988-90 TOPAZ
1991 TRACER
LIGHT TRUCK: 1985-90 BRONCO II, BRONCO
1985-91 ECONOLINE, F-150-350 SERIES
1985-92 RANGER
1986-91 AEROSTAR
1991 EXPLORER

ISSUE: Hard cold starts, hesitation and stalls on initial start-up or during idle or decel may be caused by sludge in the throttle body and/or idle by-pass valve. Sludge deposits or oil film on the throttle body bore and plate or the idle air by-pass valve may cause one or more of the following conditions.
Hard Cold Start
Stall On Initial Start-Up
Stall During Idle
Stall During Decel
Rough Idle
Rolling Idle
Hesitation During Acceleration

ACTION: A new idle air by-pass service kit (F2PZ-9F939-A) is now available for service use to correct sludge contamination concerns of the throttle bore and plate only. It eliminates the need to clean the majority of past model throttle body applications. Cleaning is not required on sludge tolerant throttle body designs released for 1991 and newer model years.

Install an idle air by-pass service kit (F2PZ-9F939-A) as applicable to provide a permanent correction for symptoms caused by throttle body sludge deposits. Refer to the instruction sheet included in the kit for installation details. Refer to Figure 1 for a specific application list of EFI (port fuel Injection) engines involved in this TSB article.

The idle air by-pass service kit (F2PZ-9F939-A) includes the following items.

One (1) Idle Adjust Spacer
Two (2) Gaskets
Two (2) Attaching Bolts
One (1) "Attention" Sticker
One (1) Instruction Sheet
Refer to the figure for the kit's components.
NOTE: EFFECTIVE WITH THIS TSB, THROTTLE BODY CLEANING IS NO LONGER COVERED UNDER 5/50 EMISSIONS WARRANTY, UNLESS AS SPECIFIED IN THE FOLLOWING APPLICATION CHARTS. FAILURE TO FOLLOW THE CORRECT PROCEDURE MAY RESULT IN THE CLAIM BEING DISALLOWED.
The idle air adjust spacer incorporates sludge tolerant design features that eliminate throttle body sludge related conditions. Once installed, throttle body cleaning is not allowed and periodic adjustment of the throttle body is not required.

CHECKS TO MAKE PRIOR TO SERVICE KIT INSTALLATION
Confirm that the following items are not causing the idle quality concern before proceeding with the service kit installation.

Contamination within the idle air by-pass solenoid
Lack of fuel system control (excessively rich or lean)
Ignition timing change
Incorrect or malfunctioning EGR system
Incorrect or malfunctioning cooling system
Vacuum leaks (air intake manifold, vacuum hoses, vacuum reservoirs, power brake booster where applicable).
EEC diagnostics have been performed and vehicle malfunction indicated service output codes have been resolved and cleared.
If any of the areas listed above are found to be at fault, correct them before proceeding with the service kit installation.

IDLE SPEED ADJUSTMENT
WARNING: BEFORE PROCEEDING WITH THE IDLE SPEED ADJUSTMENT, VERIFY THAT THE FOLLOWING ITEMS ARE TAKEN CARE OF PROPERLY.
The transmission is in PARK or Neutral.
The parking brake is applied.
The wheels are properly blocked.
The engine is at operating temperature.
The heater. A/C, cooling fan and other accessories are OFF.
The EFI throttle body idle speed adjustment procedures for the various model year passenger cars and light trucks are outlined in step-by-step procedures. Select the appropriate procedure for the vehicle involved and adjust the throttle body idle RPM accordingly, after service kit installation.

THROTTLE BODY AND IDLE AIR BY-PASS SOLENOID SERVICE PROCEDURE
Detailed application charts for throttle body and idle air by-pass solenoid service procedures by engine VIN #/engine displacement/vehicle application and model year are shown. Refer to these charts to see if the service kit is to be installed and which service cleaning procedure, if any, is to be used.

SERVICE CLEANING PROCEDURES
The following items should be noted prior to beginning the service cleaning procedure.

Confirm that the correct service cleaning procedure is identified in the Application Charts, Figures 6-11, for the vehicle/engine combination being serviced.
Do not clean throttle bodies identified to accept service kit (F2PZ-9F939-A), IDLE AIR ADJUST SPACER.
Use a 1" (25.4mm) to 1 1/2" (38.1mm) wire stemmed horse hair or nylon bottle cleaner type brush.
Use rubber gloves and eye protection.
Do not clean throttle bodies identified with a yellow/black "ATTENTION" label.
Do not clean "Black" plastic air by-pass valves. Refer to TSB 89-13-8 for service details.
Do not run vehicles with air flow meters when the air duct is removed.
Do not use carburetor cleaner as a cleaning solvent. Use Carburetor Tune-up Cleaner (D9AZ-19579-AA).

PROCEDURE #1
THROTTLE BODY AND IDLE AIR BY-PASS VALVE CLEANING
CAUTION: DO NOT RUN VEHICLES EQUIPPED WITH AIR FLOW METERS DURING THE CLEANING PROCEDURE. IF THERE IS A YELLOW/BLACK "ATTENTION" LABEL ON THE THROTTLE BODY ADVISING NOT TO CLEAN, OR IF THE VEHICLE IS IDENTIFIED AS ACCEPTING SERVICE KIT (F2PZ-9F939-A), USE PROCEDURE #2 FOR IDLE AIR BY-PASS VALVE CLEANING ONLY.
Plug the actuator into the connector in the Rotunda Cleaner/Tester, Tool 113-00009.
Remove the air duct to the throttle body inlet.
Disconnect the idle air by-pass valve signal lead.
Attach the actuator harness plug to the idle air by-pass valve.
Start the actuator and then start the engine. Do not start engines that have air flow meters.
Spray just enough Carburetor Tune-up Cleaner (D9AZ-19579-AA) into the throttle bore to wet the bore and throttle plate.
Spray the Carburetor Tune-up Cleaner for about five (5) seconds into the idle air by-pass valve inlet passage while the actuator is operating.
Stop the engine and actuator. Let everything soak for fifteen (15) minutes.
After a fifteen (15) minute soak, saturate the cleaning brush with solvent and scrub between the throttle body bore and plate while holding the throttle wide open.
NOTE: IT IS NECESSARY TO APPLY SOME PRESSURE ON THE BRUSH WHILE SCRUBBING.
Repeat saturating the brush and scrubbing for one (1) to two (2) minutes, making sure to reach into the corners where the throttle shaft meets the bore wall.
Start the actuator and the start the engine. Do not start engines that have air flow meters.
Spray Carburetor Tune-up Cleaner into the throttle bore for up to one (1) minute to wash away residue. Do not spray for longer than six (6) continuous seconds on engines that have air flow meters and are not running.
Spray Carburetor Tune-up Cleaner into the idle by-pass valve passage leading to the inlet of the valve for up to one (1) minute. Do not spray for longer than six (6) continuous seconds on engines that have air flow meters and are not running.
Stop actuator and stop engine, if running.
NOTE: MAKE SURE THE THROTTLE PLATES OPERATE FREELY AND CLOSE PROPERLY.
Reinstall the air duct.
Start and run the engine for about one (1) minute to dry out the solvent residue.
Operate the actuator to make sure the solvent is purged from the idle by-pass valve.
Disconnect the actuator from the idle air by-pass valve.
Reattach the control signal lead to the air by-pass valve.
Check engine for normal operation. It may be necessary to reset the idle speed due to a previous adjustment for an idle concern. (Refer to the respective Powertrain/Emissions Diagnosis Service Manual, Throttle Body Section, for idle speed adjust procedure.)

Alternate Cleaning Procedure for Hitachi IACs
NOTE: Method to be used only when the Rotunda Fuel Injector Tester/Cleaner 113-00001 and Air Bypass Valve Actuator 113-00009 or equivalent for the recommended method are not available.

1. Remove the idle air control valve from the throttle body.
2. Remove the electrical solenoid assembly from the mechanical portion of the idle air control valve by removing the two screws, then sliding the mechanical portion away from the solenoid.
3. CAUTION: Do not exceed three minutes soak time, and do not use choke cleaner as an internal O-ring may begin to deteriorate. Soak the mechanical portion in Carburetor Tune-Up Cleaner D9AZ-19579-BA meeting Ford specification ESR-M14P9-A or equivalent for two to three minutes maximum.
4. With the mechanical portion completely submerged, shake in all directions: up, down, right and left. Then push in on the rod that mates with the solenoid assembly, and again shake in all directions with the unit submerged and the rod held in as far as possible.
5. Remove the unit from the cleaning fluid and dry out thoroughly using shop air.

PROCEDURE #2
IDLE AIR BY-PASS VALVE CLEANING ONLY
CAUTION: THIS CLEANING PROCEDURE MAY BE USED WITH SLUDGE TOLERANT THROTTLE BODIES WHICH ARE IDENTIFIED WITH A YELLOW/BLACK "ATTENTION" LABEL AND THOSE USING SERVICE KIT (F2PZ-9F939-A). NO ATTEMPT SHOULD BE MADE TO CLEAN THROTTLE BODY BORE/PLATE AREA BY DIRECT SPRAYING OR SCRUBBING. DO NOT RUN VEHICLES WITH AIR FLOW METERS DURING CLEANING PROCEDURE.
Plug the actuator into the connector in the Rotunda Air By-Pass Valve Adapter 113-00009, or equivalent.
Remove the air duct to the throttle body inlet.
Disconnect the idle air by-pass valve signal lead.
Attach the actuator harness plug to the idle air by-pass valve.
Start the actuator and then start the engine.
NOTE: DO NOT START ENGINES THAT HAVE AIR FLOW METERS.
Spray the Carburetor Tune-up Cleaner for about five (5) seconds into the idle air by-pass valve inlet passage while the actuator is operating.
CAUTION: AVOID DIRECT SPRAYING ON THROTTLE PLATE/BORE AREA
Stop the engine and actuator. Let everything soak for fifteen (15) minutes.
Start the actuator and the start the engine.
CAUTION: DO NOT START ENGINES THAT HAVE AIR FLOW METERS.
Spray Carburetor Tune-up Cleaner into the throttle bore for up to one (1) minute.
CAUTION: DO NOT SPRAY FOR LONGER THAN SIX (6) CONTINUOUS SECONDS ON ENGINES THAT HAVE AIR FLOW METERS AND ARE NOT RUNNING.
Stop actuator and stop engine if running.
Reinstall the air duct.
Start and run the engine for about one (1) minute to dry out the solvent residue.
Operate the actuator to make sure the solvent is purged from the idle by-pass valve.
Disconnect the actuator from the idle air by-pass valve.
Reattach the control signal lead to the air by-pass valve.
Check engine for normal operation.
NOTE: IT SHOULD NOT BE NECESSARY TO RESET THE IDLE SPEED SINCE ONLY THE IDLE AIR BY-PASS VALVE WAS SERVICED IN THIS PROCEDURE

Alternate Cleaning Procedure for Hitachi IACs
NOTE: Method to be used only when the Rotunda Fuel Injector Tester/Cleaner 113-00001 and Air Bypass Valve Actuator 113-00009 or equivalent for the recommended method are not available.

1. Remove the idle air control valve from the throttle body.
2. Remove the electrical solenoid assembly from the mechanical portion of the idle air control valve by removing the two screws, then sliding the mechanical portion away from the solenoid.
3. CAUTION: Do not exceed three minutes soak time, and do not use choke cleaner as an internal O-ring may begin to deteriorate. Soak the mechanical portion in Carburetor Tune-Up Cleaner D9AZ-19579-BA meeting Ford specification ESR-M14P9-A or equivalent for two to three minutes maximum.
4. With the mechanical portion completely submerged, shake in all directions: up, down, right and left. Then push in on the rod that mates with the solenoid assembly, and again shake in all directions with the unit submerged and the rod held in as far as possible.
5. Remove the unit from the cleaning fluid and dry out thoroughly using shop air.

WARRANTY COVERAGE
Throttle bodies and idle air by-pass valves on all EFI (Port Fuel Injection) engines through the 1992 model year that can be cleaned (as identified in the application charts) are covered under 5/50 Emissions Warranty Coverage.

For those throttle bodies identified as having sludge tolerant designs or using service kit (F2PZ-9F939-A) where cleaning is not allowed per the application charts, the warranty claims for cleaning will not be reimbursed even within the 12/12 warranty coverage period. Cleaning is not allowed. Service kit installation (single time) is covered under 5/50 emission warranty.

LABOR STANDARDS OPERATIONS
The labor operations shown in the following Operation/Description/Time columns are identified by procedure number and vehicle line. Specific engines for various vehicles are identified in the sludge cleaning procedure application charts. The throttle body cleaning operations with combinations and the air by-pass valve cleaning combinations will appear in future Labor Manuals under the following operation numbers.

9926 B - Throttle body and idle air by-pass valve cleaning
9926 B2 - Adjust idle speed
9715 A - Air by-pass valve cleaning only
9715 A1 - Adjust idle speed

PART NUMBER PART NAME
F2PZ-9F939-A Idle Air By-pass Service Kit
D9AZ-19579-AA Carburetor Tune-Up Cleaner

OTHER APPLICABLE ARTICLES: 89-13-8
SUPERSEDES: 88-24-5, 88-24-6, 89-16-5, 91-10-9, 91-7-4
WARRANTY STATUS: Eligible Under Warranty Coverage As Stated In The Text Of This Article

OPERATION DESCRIPTION TIME
912507A Idle Air By-Pass Valve Cleaning - 1983-85 Escort, EXP, LN7, LYNX 1.6L EFI. 0.5 Hr.
912507B Idle Air By-Pass Valve Cleaning - 1986-91 Escort 1.9L EFI, 1986/87 EXP, Lynx 1.9L EFI, 1991 Tracer 1.9L EFI. 0.5 Hr.
912507C Idle Air By Pass Valve Cleaning - 1984-87 Mustang 2.3L T/C, 1986/87 Capri, Cougar 2.3L T/C, 1984-88 T-Bird 2.3L T/C, 1987/92 Mustang 2.3L EFI. 0.5 Hr.
912507D Idle By-Pass Valve Cleaning - 1988-91 Tempo, Topaz 2.3L HSC, 1985-92 Ranger 2.3L EFI. 0.6 Hr.
912507E Idle Air By-Pass Valve Cleaning - 1986/87 Aerostar 2.3L EFI, 1985 Bronco II 2.3L EFI. 0.7 Hr.
912507F Idle Air By-Pass Valve Cleaning - 1986-90 Bronco II 2.9L EFI, 1986-92 Ranger 2.9L EFI. 0.7 Hr.
912507G Idle Air By-Pass Valve Cleaning - 1991/92 Probe 3.0L EFI, 1986-91 Taurus 3.0L EFI, 1987-91 Sable 3.0L EFI. 0.6 Hr.
912507H Idle Air By-Pass Valve Cleaning - 1986-91 Aerostar 3.0L EFI, 1991 Ranger 3.0L EFI. 0.7 Hr.
912507I Idle Air By-Pass Valve Cleaning - 1988 Continental, Cougar, Taurus, T-Bird, Sable 3.8L EFI. 1988 Cougar, T-Bird 3.8L S/C. 0.6 Hr.
912507J Idle Air By-Pass Valve Cleaning - 1990-92 Aerostar 4.0L EFI, 1990 Bronco II 4.0L EFI, 1991/92 Explorer 4.0L EFI, 1990-92 Ranger 4.0L EFI. 0.7 Hr.
912507K Idle Air By-Pass Valve Cleaning - 1987-92 Bronco 4.9L EFI, 1987-92 F-Series 4.9L EFI, 1987/90 Econoline (Without Rear Heater) 4.9L EFI, 1991/92 Econoline (All) 4.9L EFI. 0.7 Hr.
912507L Idle Air By-Pass Valve Cleaning - 1986-88 Cougar, T-Bird 5.0L EFI, 1986-87 Continental, Mark VII 5.0L EFI, 1986/91 Crn - Victoria, Grn - Marquis 5.0L EFI, 1986-92 Mark VII 5.0L HO, 1982-92 Mustang 5.0L HO. 0.6 Hr.
912507M Idle Air By-Pass Valve Cleaning - 1985-92 Bronco, E-Series, F-Series 5.0L EFI. 0.7 Hr.
912507N Idle Air By-Pass Valve Cleaning - 1988-90 Bronco, F-Series 5.8L. 1991 Econo, F-Series, Bronco 5.8L (Do not Clean Solenoid, Calib; 1-64E-R10,1-64H-R10,1-64J-R10,1-64K-R10,1-64M-R10,1-64P-R10,1-64R-R10,1-75A-R00,1-76A-R00,1-76B-R00,1-76C-R00) 0.7
912507O Idle Air By-Pass Valve Cleaning - 1991/92 F And B Series, 7.0L EFI. 0.7 Hr.
912507P Idle Air By-Pass Valve Cleaning - 1987-92 E-Series, F-Series 7.5L EFI. 0.7 Hr.
912507Q Throttle Body And Idle Air By-Pass Valve Cleaning - 1989/90 Probe 3.0L EFI. 0.9 Hr.
912507R Throttle Body And Idle Air By-Pass Valve Cleaning - 1987-90 Econoline (With Rear Heat) 4.9L EFI. 0.8 Hr.
912507S Throttle Body And Idle Air By-Pass Valve Cleaning - 1988-90 Econoline 5.8L EFI. 0.9 Hr.
912507T Service Kit Install - All Cars And Light Trucks (Except Aerostar And Econoline) - Refer To The Service Procedure Application Charts, For Vehicle Application. 1.0 Hr.
912507U Service Kit Install - Aerostar, Econoline - Refer To Service Procedure Application Charts - For Vehicle Application. 1.2 Hr.

For other TSBs, check here.
_______________________________________________________
Idle Air Trim

Idle Air Trim is designed to adjust the Idle Air Control (IAC) calibration to correct for wear and aging of components. When engine conditions meet the learning requirement, the strategy monitors the engine and determines the values required for ideal idle calibration. The Idle Air Trim values are stored in a table for reference. This table is used by the PCM as a correction factor when controlling idle speed. The table is stored in keep alive memory (KAM) and retains the learned values even after the engine is shut off. A Diagnostic Trouble Code (DTC) is output if the Idle Air Trim has reached its learning limits.

Whenever an IAC component is replaced or cleaned or a service affecting idle is performed, it is recommended that keep alive memory be cleared. This is necessary so the idle strategy does not use the previously learned Idle Air Trim values. It is important to note that erasing DTCs with a scan tool does not reset the Idle Air Trim table.

Once keep alive memory has been reset, the engine must idle for 15 minutes (actual time varies between strategies) to learn new idle air trim values. Idle quality will improve as the strategy adapts. Adaptation occurs in four separate modes. The modes are shown in the following table.

IDLE AIR TRIM LEARNING MODES
Transmission Range - Air Conditioning Mode
NEUTRAL - A/C ON
NEUTRAL - A/C OFF
DRIVE - A/C ON
DRIVE - A/C OFF

Idle Speed Control Closed Throttle Determination

One of the fundamental criteria for entering rpm control is an indication of closed throttle. Throttle mode is always calculated to the lowest learned throttle position (TP) voltage seen since engine start. This lowest learned value is called "ratch," since the software acts like a one-way ratch. The ratch value (voltage) is displayed as the TPREL PID. The ratch value is relearned after every engine start. Ratch will learn the lowest, steady TP voltage seen after the engine starts. In some cases, ratch can learn higher values of TP. The time to learn the higher values is significantly longer than the time to learn the lower values. The brakes must also be applied to learn the higher values.

All PCM functions are done using this ratch voltage, including idle speed control. The PCM goes into closed throttle mode when the TP voltage is at the ratch (TPREL PID) value. Increase in TP voltage, normally less than 0.05 volts, will put the PCM in part throttle mode. Throttle mode can be viewed by looking at the TP MODE PID. With the throttle closed, the PID must read C/T (closed throttle). Slightly corrupt values of ratch can prevent the PCM from entering closed throttle mode. An incorrect part throttle indication at idle will prevent entry into closed throttle rpm control, and could result in a high idle. Ratch can be corrupted by a throttle position sensor or circuit that "drops out" or is noisy, or by loose/worn throttle plates that close tight during a decel and spring back at a normal engine vacuum.