V8 IAC & TPS
The stop screw is red-threadlocked because it should NEVER be adjusted. It does NOT control idle speed; it prevents the throttle butterflies from binding in the throttle bores. If it has been tampered with, follow the procedure below to reset it correctly.
The TPS is usually fastened by PoziDrive screws, which look very similar to Phillips. But a Phillips bit does not fit correctly, and will usually round the screw heads (which are also threadlocked). Identify the screw before selecting a tool to remove them.
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How to adjust idle speed (official Ford procedure)
Engine Idle Speed Check & Adjustment - Follow this procedure as directed step-by-step, noting the applicability of each step. Skipping through the procedure will result in abnormal idle & possibly other driveability symptoms.
AIS7
Verify that the following engine systems have been properly diagnosed and corrected before proceeding with the Air Intake System diagnostics:
- Positive Crankcase Ventilation (PCV) System.
- Exhaust System.
- Ignition System (Refer to maintenance schedule).
- Engine Cooling System (engine coolant temperature is above 160 degrees F).
- Fuel pressure, fuel filter, fuel quality (contamination).
AIS8
Key on, engine running with engine at idle, listen for vacuum leaks. Inspect the entire inlet air system from the Mass Air Flow (MAF) sensor to the intake manifold for leaks such as:
- Cracked or punctured outlet air tube or air cleaner housing assembly.
- Loose connections on the inlet air tube at the air cleaner housing or throttle body.
- Idle Air Control (IAC) valve assembly or gasket seal.
- Intake manifold assembly or gasket seal.
- EGR valve diaphragm or control solenoid.
- EGR valve gasket seal leak to intake manifold.
- Vacuum supply connectors and hose.
- PCV connectors and hose.
AIS9
NOTE: Engine idle RPM is controlled by the PCM and cannot be adjusted. This test will verify the idle rpm is within the specification. If the engine is allowed to idle for an extended period of time, or if the engine temperature is hot enough to require cooling fan operation, it may be necessary to turn the engine off and repeat this test procedure.
- Transmission in Park (wheels blocked and parking brake engaged).
- A/C, heater and all accessories are off.
- Key on, engine running.
- Engine at normal operating temperature and cooling fan off.
WARNING: DO NOT UNPLUG COOLING FAN. IT MAY CAUSE ENGINE OVERHEATING.
Idle RPM Check
NOTE: Idle rpm check should only be performed after Diagnostic Test Steps AIS7 through AIS9 have been completed.
- Transmission in PARK or NEUTRAL.
- Parking brakes applied (automatic brake release disconnected where applicable).
- Driving wheels blocked.
- Generator belt tension.
- Heater and accessories off.
- Throttle lever resting on the throttle plate stop screw.
- EEC-IV diagnostics performed and vehicle malfunction indicated by Diagnostic Trouble Codes (DTCs).
NOTE: For additional information, refer to Fuel/Engine Group in the Car or Truck Service Manual.
NOTE: The curb idle and fast idle RPMs are controlled by the Powertrain Control Module (PCM) and the Idle Air Control (IAC) valve. The Idle Air Control (IAC) valve is not adjustable. A large increase or decrease in closed plate airflow from the calibrated level will not allow this device to effectively control the rpm.
Throttle bodies with sludge tolerant design are clearly identified with a yellow/black attention decal. Refer to Figure 23 for the location of decal. This decal advises that the throttle return screw must not be adjusted counter-clockwise (backed off), as this will not reduce the engine speed but may cause the throttle plate to stick in the bore in the closed (idle) position. Backing out the screw may be required if the throttle body had been previously serviced (a plug may be present in the throttle plate orifice) or if the throttle return screw has been tampered with (TP sensor self-test output out of range), refer to the appropriate procedure for details. The decal also advises that these throttle bodies must not be cleaned inside the bore, as cleaning will impair the sensitive coating. The sludge accumulation will not affect the throttle body idle air flow. (The cleaning procedure for the Idle Air Control (IAC) valve may still apply. Refer to the Service Manual.)
Throttle bodies should not be cleaned because cleaning will remove the sludge tolerant coating.
Follow these steps to service the throttle body:
1. Remove the throttle body.
2. Hold it up to a light. No light should be visible between the plate and bore with the throttle plate closed. The hole in the plate should be visible and unobstructed.
3. Rotate the throttle lever and allow it to return. It should not stick or bind. It should return to the closed plate (idle) position freely when released.
If the problem cannot be corrected (an obstruction cannot be removed, free sticking, etc.), the throttle body must be replaced.
Procedure Selection Chart: (The 1995 applications with self-test idle rpm check use procedure A; those without use procedure B.)
ENGINE - - - - - - - - - VEHICLE - - - - - - - PROCEDURE
3.0L - - - - - - - - - - - Aerostar - - - - - - - - - - B
4.0L - - - - - - - - - - - Aerostar - - - - - - - - Not Adjustable
4.9L - - - - - - - - - - - - All - - - - - - - - - - - - - A
5.0L MFI - - - - - - - - - Non E4OD - - - - - - - - - B
5.0L MFI - - - - - - - - - - E4OD - - - - - - - - - - - A
5.0L SFI - - - - - - - - - - AODE - - - - - - - - - - - A
5.8L - - - - - - - - - - - - All - - - - - - - - - - - - - A
7.0L MFI - - - - - - - - - - All - - - - - - - - - - - - - A
7.5L MFI - - - - - - - - - - All - - - - - - - - - - - - - B
Procedure A
1. Activate engine running self-test. See this page.
2. After DTC slow code output is completed, unlatch and within 4 seconds latch the STI button. (If using a jumper wire in the DLC, remove it for LESS than 4 sec.)
3. A single pulse code indicates the entry mode, then observe the Self-Test Output (STO) of the STAR Tester in Item 4. If adjustment is required in Item 4, refer to possible causes listed in A1S7 and A1S8 and correct them as required.
Continue with this procedure if necessary.
4. Observe STAR tester or CEL or other indicator.
- A. Constant tone, solid light or "STO LO" readout means base idle rpm is within range. To exit test, unlatch STI button , then wait four seconds for reinitialization (after 10 minutes it will exit by itself).
- B. Beeping tone, flashing light, or "STO LO" readout at (8 Hz) indicates TP sensor is out of range due to over adjustment; adjustment may be required.
- C. Beeping tone, flashing light, or "STO LO" readout at (4 Hz) indicates base idle rpm is too fast, adjustment is required, go to step 6.
- D. Beeping tone, flashing light, or "STO LO" readout at (1 Hz) indicates base idle rpm is too slow, adjustment is required, go to step 5.
5. If rpm is too slow, follow applicable procedure for the engine being serviced.
- A. Do not clean the throttle body. Turn the air trim screw counter-clockwise until conditions in step 4(A) are satisfied.
- B. Do not clean the throttle body. Check for the plate orifice plug. If there is no plug, turn throttle return screw clockwise until conditions in Step 4(A) are satisfied. If there is a plug from previous service, remove plug and then adjust screw in either direction as required. Screw must be in contact with the lever pad after adjustment.
6. If rpm is too high, follow applicable procedure for the engine being serviced.
- A. Do not clean the throttle body. Turn the air trim screw clockwise until conditions in Step 4(A) are satisfied.
- B. Turn engine OFF.
- - a. Block off the orifice in the throttle plate temporarily with tape. If the orifice already has a plug from previous service, go to Step (c).
- - b. Restart the engine and check idle speed using Self-Test (mass air packages require air intake hose to be reattached first). If engine stalled, crack open the plate by turning the throttle return screw clockwise.
- - c. If rpm continues to be fast, perform test in Step 7. If TP sensor DTC is within range, remove tape, go to Section 2A for other causes. If out of range, adjust throttle return screw for proper TP sensor DTC code (lever pad must be in contact with screw after adjustment). If rpm is still fast, terminate this procedure and go to Section 2A for other possible causes.
- - d. However, if rpm drops to or below the desired level, as indicated by Self -Test Output tone, turn the engine off, disconnect air cleaner hose, remove the tape.
- - e. Install the plug with proper color code depending on throttle plate orifice size (refer to the end of this section).
- - f. Reconnect the air cleaner hose - start the engine, turn the throttle return screw clockwise (do not turn it counter -clockwise as this may cause the throttle plate to stick at idle) until conditions in Step 4(A) are satisfied.
7. Run KOEO Self-Test for proper TP sensor DTC.
8. Verify the throttle plate is not stuck in the bore at idle position and linkage is not preventing throttle from closing.
9. On Automatic Overdrive Transmission (AOD) applications, check TV pressure adjustment.
Procedure B
1. Engine off, disconnect the negative (-) terminal of the battery for five minutes, then reconnect it.
2. Start engine and stabilize for two minutes, then goose engine and let it return to idle. Lightly depress and release the accelerator and let engine idle. NOTE: If electric fan comes on, wait until it turns off.
3. If engine idles properly, exit this procedure.
4. Unplug SPOUT line (except 7.5L) and verify ignition timing is base ±2 deg BTDC (refer to VECI decal).
7. Disconnect the Idle Air Control (IAC) solenoid
8. Start engine and run at idle for 120 sec (7.5L - 2500 rpm for 30 sec).
9. Place automatic transmission in PARK, manual transmission in NEUTRAL.
10. Check idle rpm to the range using tachometer. 5.0L MFI Truck Non-E4OD: Auto 675±50 Man 700±50; 7.5L: 650±50
- A. If rpm is too low, do not clean the throttle body. Check for the plate orifice plug. If there is no plug, turn throttle return screw clockwise to the desired rpm ±25. If there is a plug from previous service, remove plug and then adjust screw in either direction as required. Screw must be in contact with the lever pad after adjustment.
- B. If rpm is too high, turn engine off.
- - a. Disconnect air cleaner hose.
- - b. Block off the orifice in the throttle plate temporarily with tape. If the orifice already has a plug from previous service, go to Step f. If the orifice does not have a plug, go to Step e.
- - c. Restart the engine and check idle speed using a tachometer (mass air applications will require air cleaner hose to be reattached before rpm check). If engine stalled, crack open the plate by turning throttle return screw clockwise. Do not over adjust.
- - d. If rpm continues to be fast, perform test in Step 18. If TP sensor DTC is within
range, remove tape, go to Section 2A for other causes. If out of range, adjust throttle return screw for proper TP sensor DTC. Lever pad must be in contact with the screw. If rpm is still fast, terminate this procedure and go to Section 2A for other possible causes.
- - e. If rpm drops to value in Step 10 or below, or engine stalls, turn the engine off, disconnect air cleaner hose, remove the tape.
- - f. Install the plug with proper color code depending on orifice size (refer to the end of
this Section).
- - g. Reconnect the air cleaner hose - start the engine. Check idle rpm using a tachometer. Turn the throttle return screw clockwise (do not turn it counter-clockwise as this may cause the throttle plate to stick at idle) to the nominal rpm ± 25 shown in Step 10.
11. Shut engine off and repeat steps 8, 9 and 10.
12. Remove the feeler gauge between plate stop screw and throttle lever.
13. Shut engine off and disconnect battery for 10 minutes minimum.
14. Reconnect SPOUT line (except 7.5L).
15. Remove Rotunda tool. Unplug PCV hose. Reconnect CANP and PCV hoses to the intake manifold.
16. Engine off, reconnect Idle Air Control solenoid, verify the throttle plate is not stuck in the bore at idle position and linkage is not preventing throttle from closing.
17. Start engine and stabilize for two minutes, then goose engine and let it return to idle. Lightly press and release the accelerator and let engine idle. If idle problem still persists, go to Section 2A for other possible causes.
18. Run KOEO Self-Test for proper TP sensor DTC.
19. On Automatic Overdrive Transmission (AOD) applications, check TV pressure adjustment.
Throttle Plate Orifice Plug Service Installation Procedure
1. Remove air inlet tube(s) from throttle body.
2. Select the proper color plug by using the Go/No-Go gauge pegs included with the service kit F0PZ-9F652-A. (Refer to Figure.)
3. Starting with the largest diameter gauge peg, attempt to insert it through the throttle plate orifice.
4. If the gauge peg goes through the orifice, use the corresponding color plug. If it does not go through, proceed with the next smaller gauge peg for Go/No-Go Test.
NOTE: It is important that the largest Go/No-Go combination is used to determine the proper plug size.
5. If the smallest gauge peg does not go through the orifice, use the reamer bit and handle included with the service kit to enlarge the plate orifice. Wipe bearing grease on both sides of the plate orifice and on the reamer bit to hold the brass chips. After reaming, wipe the plate clean and then return to Step 3 to determine the proper plug size.
6. Using the installation tool from the service kit, apply some bearing grease to the tip of the tool to help hold the plug on the tool, then push the plug into the orifice until it bottoms out at the throttle plate.
7. Open and snap shut the throttle several times to verify proper plug retention.
8. Reconnect air inlet tube(s).
9. Reset idle rpm per engine requirement using the throttle return screw.
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After adjusting the throttle stop, check the TPS range:
For the IAC cleaning procedure, see this caption:
For IAC replacement, see this caption:
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.
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