Tuneup

Maintenance
Schedule

Lubricants
and Capacities

Set Timing

Solving Idle Problems

1. Cleaning your IAC
2. Cleaning your throttle body
3. Resetting the base idle
4. TPS Voltage
5. Cleaning the MAF wire

Clutch Replace

VIN Explained

Vehicle Certification
Label Explained

STEERING SYSTEM DIAGNOSIS AND TESTING
- Wander --Condition where the vehicle wanders side-to-side on the roadway
  - NOTE:
    Evaluation should be conducted on a level road (little road crown).
  - Possible Source(s):
  - Tire size and pressure.
    - Be sure tire sizes are correct and adjust tire pressures.
  - Vehicle is unevenly loaded or overloaded.
    - Adjust load.
  - Loose/worn tie rod ends or ball socket.
    - Replace tie rod end or tie rod assembly as necessary.
  - Steering gear mounting insulators and/or retaining bolts loose or damaged.
    - Replace bolts.
  - Loose suspension struts or ball joint(s).
    - Replace arm and ball joint assembly.
  - Column intermediate shaft connecting bolts loose.
    - Tighten at steering gear and at column.
  - Column intermediate shaft joints loose/worn.
    - Replace intermediate shaft assembly.
  - Improper wheel alignment.
    - Adjust as required.
- Pulls to One Side --A condition where the vehicle tends to pull to one side when driven on a level surface
  - Possible Source(s):
  - Improper tire pressure.
    - Adjust tire pressure.
  - Improper tire size or different type.
    - Replace as required.
  - Vehicle is unevenly or excessively loaded.
    - Adjust load.
  - Improper wheel alignment.
    - Adjust as required.
  - Damaged front suspension components.
    - Front suspension component replacement.
  - Damaged rear suspension components.
    - Rear suspension component replacement.
  - Steering gear valve effort out of balance.
    - Place transmission in NEUTRAL while driving and turn engine off (coasting). If vehicle does not pull with the engine off, replace the steering gear valve assembly. Refer to ŤSection 11-02ť.
    - If vehicle does drift with engine off:
    - --Cross switch front tire/wheel assemblies.
    - --If vehicle pulls to opposite side, cross switch tire/wheel assemblies that were on the rear to same side on the front.
    - --If vehicle pull direction is not changed, check front suspension components and wheel alignment.
  - Front and/or rear brakes for operating improperly.
    - Adjust if necessary.
  - Bent rear axle housing or damaged or sagging springs in the front and/or rear suspension.
    - Replace if necessary.
  - Rear suspension loose/worn shock absorber struts, suspension arm retaining fasteners.
    - Tighten all retaining fasteners.
- Feedback --Condition where roughness is felt in the steering wheel when driven over rough pavement.
  - Possible Source(s):
  - Column intermediate shaft joints loose/worn.
    - Replace intermediate shaft assembly.
  - Loose tie rod end(s) and/or tie rod inner ball joints.
    - Replace tie rod end(s).
  - Steering gear mounting insulators and/or retaining bolts loose or damaged.
    - Replace retaining bolts and tighten.
  - Column intermediate shaft connecting bolts loose.
    - Tighten bolts to specification at steering gear 19-27 N-m (14-20 lb-ft) at column intermediate shaft 27-40 N-m (20-30 lb-ft).
  - Loose suspension bushings/fasteners or ball joints.
    - Tighten suspension fasteners, replace worn bushings, or replace ball joints.
  - Check column conditions.
- Power Steering Pump Leaks
  - Possible Source(s):
  - Excessive fluid fill.
    - Adjust fluid to proper level.
  - Dipstick missing, loose, damaged or missing O-ring.
    - Service or replace, if required.
  - Broken/cracked reservoir.
    - Replace reservoir.
  - Loose or damaged hose fittings.
    - Service or replace.
  - Leakage at shaft seal:
    - Replace power steering pump.
  - Shaft seal not pressed in flush with housing surface.
    - Use an appropriate seal installation tool to correct installation; if not possible or still leaking, replace seal.
  - Seal damage.
    - Replace seal.
  - Rotor shaft damage, such as helical grooving or the OD has an axial scratch.
    - Replace shaft and seal.
  - Shaft bushing worn.
    - Replace plate and bushing assembly.
  - Plugged drainback hole.
    - Disassemble power steering pump and clean drainback hole. If hole is not drilled through, replace plate and bushing assembly.
  - Damaged or missing reservoir O-ring.
    - Replace O-ring.
  - Damaged or missing outlet fitting O-rings.
    - Replace O-rings.
  - Loose outlet fitting.
    - Tighten as required.
  - Outlet fitting damaged.
    - Replace outlet fitting.
  - Excessive pump assembly bracket vibration.
    - Correct bracket alignment and tighten bracket bolts.
  - Plate and bushing reservoir seal groove porosity/damage, metal chips or foreign material on seal or in seal groove.
    - Clean groove; replace plate and bushing assembly if damaged.
- Belt Squeal --Particularly at full wheel travel and stand still parking)
  - Possible Source(s):
  - Loose belt.
    - Adjust belt tension to specification.
- Chirp Noise in Power Steering Pump
  - Possible Source(s):
  - Loose or worn belt.
    - Adjust belt tension to specification or replace belt.
- Swish Type Noise
  - Possible Source(s):
  - A noise created by the flow of excessive fluid into the bypass port of the pump valve housing (with temperature below 130°). The shearing effect of the cooler (heavier) oil is not detrimental to pump operation. A normal condition. Noise will diminish with fluid temperature increase.
- Power Steering Pump --No or Poor Assist
  - Possible Source(s):
  - Contamination
    - Can be caused by foreign objects in the reservoir or power steering pump, or metallic particles being generated by cam pack discrepancies. System must be flushed thoroughly when installing a serviced or new pump.
- Moan or Whine Type Noise
  - Possible Source(s):
  - Fluid aeration.
    - Purge the power steering system to reduce aeration noise. Refer to purging procedure as outlined.
  - Pump brackets loose or misaligned.
    - Tighten or align as required.
  - Low fluid.
    - Check fluid level.
  - Hose grounded.
    - Check for hose being grounded.
  - Column grounded.
    - Check column alignment.
  - Damaged internal components.
    - Replace power steering pump.
- Gear Hiss
  - Possible Source(s):
  - Check column intermediate shaft and gear for alignment and binding.
    - Adjust column and/or intermediate shaft.
  - Check for grounded or loose boot at dash panel.
    - Align boot or tighten fasteners as required.
  - Input shaft and valve assembly.
    - Replace--only if noise is extremely objectionable.
- Noise/Rattle --Steering Column
  - Possible Source(s):
  - Loose bolts/attaching brackets.
    - Tighten.
  - Looseness of ball bearings or insufficient lube.
    - Lube or replace bearings.
  - Steering shaft insulators cracked or dry.
    - Replace or lube insulators as required.
  - Flex coupling compressed or extended.
    - Reposition shaft assembly to flatten flex coupling.
- Noise/Squeak or Cracks --Steering Column
  - Possible Source(s):
  - Dry bushings.
    - Lube shaft seal and shift tube seal.
  - Loose or mispositioned shrouds.
    - Tighten or reposition shrouds as required.
  - Steering wheel rubbing against shrouds.
    - Replace shroud(s) or wheel or reposition shrouds as required.
  - Dry shift lever grommets.
    - Lube grommets.
  - Insufficient lube on speed control slip ring.
    - Lube slip ring.
  - Upper or lower bearing sleeve out of position.
    - Reposition bearing sleeve.
- Excessive Travel of Shift Lever -- Out of Park Detent with Steering Column Locked
  - Possible Source(s):
  - Shift cane spacer clip too small or missing.
    - Replace or add spacer clip.
- Ignition Lock Cylinder Binds --in Lock and/or Accessory Position
  - Possible Source(s):
  - Shift cane spacer clip too large.
    - Replace spacer clip.
- Chatter Type Noise
  - Possible Source(s):
  - Chipped corners on rotor outside diameter or distorted slipper ring.
    - Replace rotor assembly.
- Other Causes of Noise
  - Possible Source(s):
  - Improper assembly of components such as slippers.
    - Rebuild pump and replace components as required.
  - Imperfections on rotor outside diameter or rotor end surface.
    - Replace rotor assembly.
  - Damaged rotor splines.
    - Replace rotor assembly.
  - Hairline crack on cam inner surface.
    - Replace cam rotor assembly.
  - Interference between rotor and cam.
    - Replace rotor assembly.
  - Excessively worn or scored pumping elements and rotor.
    - Replace rotor assembly and pressure plates.

MAINTENANCE AND TUNEUP PART 1
- We here the words "Tune It" lots of times, but what's really a good tune-up for your stang? The most common answer is change filters, oils and plugs, and that's what most shops and dealers will do. In this article we want to show you how to perform a HI-PERFORMANCE TUNE UP, that will leave your mustang in top shape.
  
  So what's involved in this kind of tune up?
  - 1. CLEANING THE ENGINE COMPARTMENT
    - One really easy way to clean the engine is to use "simple green" or equivalent type of de greaser. We encourage you to use only "environmentally safe" stuff.
    - First you have to cover some stuff that might be damaged by water such as the wiring harness connectors and that K&N you have exposed under the hood (in some cases). Use a plastic bag for the K&N and aluminum foil to wrap the connectors. Don't worry about the distributor since you will change wires and cap later.
    - Apply the cleaning solution liberally to the engine using a sponge, work your way under all small crevices, accessories etc, etc. Also apply to the hood insulation, this sucker gets pretty dirty.
    - Now wait for 15-20 minutes for the stuff to start working, then use a hose to wash off all that dirt. Start the engine and let it idle for 10 minutes so the water evaporates. Use an old T-shirt to completely dry the engine. Aluminum parts will stain if you leave water on them.
  - 2. AIR FILTER
    - If you have a K&N, this is the time to clean it, but use only the K&N cleaning and oiling products. If you have a stock air filter then get a K&N!!
  - 3. PLUGS AND WIRES
    - Next is changing your plugs, wires and distributor cap& rotor (5.0s), start by changing the cap and rotor, replace by first swapping the OLD wires to the new cap, check that the wires are replaced in the same order, the cap has a mark for #1 piston. Now loosen the old cap and replace the rotor, make sure there's no water in there.
    - Now change the plugs, this is the "fun part" cause it is not that easy to remove the plug wire boots from the plugs. Use mechanics or leather gloves to do this, your hands will thank you. Start by calibrating your new plugs, we recommend you to use AUTOLITES #24 on 5.0s, stay away from "sh*tfires" ouch..I mean SplitFires and similar types of plugs, also stay away from platinum's. If you cant find Autolites use Motorcraft's. Gap them to .052 4.6 and DOHC's should use platinum's, buy Bosch or NGK's.
    - Btw, don't remove your wires if you don't know the firing order, just place the old wire boots over the new plugs without pushing them all the way.
    - Change the plug wires now, do it one by one until all are replaced and don't forget the coil wire. Here we recommend to try the FMS 9mm, Accel 300 or LiveWires. Or choose the brand of your choice. Buying a thermo insulation for your wires and boots is a wise thing to do if you have Equal length headers and if you want your wires to last longer.
    - After this step, start your engine to check for possible arcing on the wires. Make sure the boots are all the way down on the plugs.
  - 4. CHANGE THE OIL
    - This you can do at home with simple tools, an oil filter removal wrench and a large pan to drain the old oil. Our recommendation is to have your oil changed at a place where they have the tools and oil recycling facilities. It takes 30 minutes and it is not that expensive. Our recommendation is to go with Synthetic oils, they last longer and have better heat dissipation qualities. Try Mobil 1, we have had great results with it. Just stay away from PTF (Teflon) loaded oils, such as Slick-50, they can clog your filter and oil passages. For the filter get a MOTORCRAFT one, stay away from FRAM and the cheap ones. Not all filters are alike.
  - 5. RADIATOR AND THERMOSTAT
    - Flush your radiator and change your Thermostat, Here start by removing the Coolant drain plugs on the block and opening the radiator flush (on front lower passenger side).
    - Remove the thermostat by loosening the 2 bolts and removing the water pump and radiator hoses that connect to the thermostat housing. Remove all the gasket material at the lower intake and thermostat housing, you can use a sharp knife or exacto knife to do this.
    - Install the thermostat housing without a thermostat or gasket, place the block drain plugs in place, re-attach the hoses and fill the system with water using a hose. Start the engine with the water running, open the radiator drain. This will flush most of the gunk out of the system. Let it run for a few minutes and Drain the system completely again.
    - Now install your new thermostat and new gasket. But first some important notes about Thermostats
    - Not all thermostats are created equal, the "cheap" ones are not a good choice since they will not open and close exactly at the same temperature and water pressure, you best bet here is to buy a "BALANCED" thermostat such as the ones sold by Mr.Gasket, this thermostat has a special construction that makes them open and close exactly at the same temperature regardless of pressure. They will also not get stuck, we have seen lots of new cheap thermostats do this after a few days or even hours.
    - Make sure you place that thermostat in the right direction, the spring side goes to the lower intake. Good thermostats have an arrow pointing which side goes to the radiator.
    - Now assemble everything back, put the block drain plugs in place and close the drain on the radiator, start the engine and fill the radiator with a mix of coolant and water, here just a few notes, if you are on a HOT location, use a 70% water 30% coolant mix, on colder areas increase the coolant to a 50-50 mix. Also on hot places use "Water Wetter" for added cooling efficiency, this stuff can lower the temp as much as 10-15 degrees.
    - Start the engine with the radiator cap removed, add water/coolant mix until it is completely full and you don't see any more air bubbles. Also fill the drain bottle to the top. Take the car for a spin for a few minutes and check coolant again. The level on the drain bottle might go down until all the bubbles are out of the system. Re-check the coolant level for the next couple of days and inspect for possible leaks at the thermostat housing gasket, if so re-tighten the bolts a bit, but not much as you can break the housing.
  - 6. SET THE TIMING
    - Setting your timing is important from a performance stand point, when you increase timing a bit, you improve the combustion efficiency. Setting timing can only be accomplished MANUALY on 5.0 engines. 4.6 owners should either get a chip or buy a special timing wheel to adjust it. We don't recall the name of this piece but we will look for it and let you know.
    - An increase in timing can make your car DETONATE or ping, this is caused by a larger need of fuel by the engine or a need for higher octane fuel. Your timing should be increased to a point where you don't hear detonation and where your car makes the most power. Since not all are created equal some respond better to advance and some others don't. High altitude Calibrated EEC's on 5.0s starting with serial #F4AE, are more prone to detonation that the series #F4ZF which are low altitude. Above your DOOR TAG you might find another small tag that says CALIBRATION CODE, with 2 numbers, the lower one is your PCM series number. If you cant find it there then you can find the EEC at the passenger side kick-panel.
    - The timing process can be found here.
      - With the engine OFF, remove the TIMING PLUG orSPOUT connector that is found on the passenger side close to the Air box. The plug is most of the times a GRAY fuse like thing that's inside a connector on a wiring harness. Now loosen the distributor bolt so that the distributor can move by hand. The bolt shouldn't be too loose as to allow the distributor to move alone.
      - To set the timing you will need a TIMING LIGHT, if you don't have one then buy, rent, or ask your neighbor for one (even if he has a Ch*vy).
      - Place the timing light "pick-up" at the #1 plug wire, the #1 is marked on the distributor cap. Connect the (+) and (-) terminals to the battery if the timing light is not a battery operated one.
      - Now locate the crank balancer wheel, it has marks to tell you advance and retard, if they are not visible try painting them with white paint from 0 to 15 degrees.
      - Start the engine, (with the spout connector unplugged)point the timing light to the wheel and move your dist clockwise to advance the timing, start at 15 degrees and stop. Stop the engine and put back the SPOUT. Test your car, drive around for awhile. If you hear detonation or pinging retard 1 degree until it stops. Also try using higher octane Gas (92-93) to stop the detonation. Make sure you disconnect the battery to clear all stored memory tables in the EEC.
  - 7. CLEAN THE THROTTLE BODY AND INTAKE
    - The Throttle body and Intake can get pretty dirty after a while, the oil and gunk deposits in them can reduce your pony's performance. Also after lots of traffic driving your heads and valves might get covered with Carbon deposits that can cause PRE-IGNITION, which is as bad as detonation.
    - To clean it all there are a few things you can do, either remove the intake and heads to clean them OR the EASY WAY. use Carb Cleaner or BRAKE FLUID to clean them. If you use Carb cleaner just make sure it is O2 sensor-safe. Brake fluid is.
    - This procedure is for 5.0 engines only,4.6 should not try this.
    - Now disconnect the hose that runs from the passenger side valve cover on the OIL FILL TUBE to the Throttle body hose. Disconnect at the valve cover side.
    - Start your engine and either SPRAY the carb cleaner into the hose or Immerse the hose in the brake fluid bottle. Do this 1 second at a time and rev the engine a bit if it starts to stall, repeat the procedure until you are half way on the cleaner or brake fluid.
    - You will see lots of smoke from the exhaust..this is normal and a sign that the cleaner is working.Take the car for a ride and repeat the procedure the next day.
  - 8. BRAKE FLUID REPLACEMENT
    - Brake fluid replacement and bleeding is something you should do at least every year. Brake fluid absorbs moisture from the exterior, that moisture can create rust inside the brake system making it less efficient. To drain the system you have 2 choices, one is to get your car to specialized shop that can drain it without leaving bubbles in the ABS (if so equipped). This is hard to do.
    - Your second choice is do it at home and try to replace most of the fluid with new one.
    - Start by getting some decent synthetic fluid, 3 or 4 small bottles is all you need, we here also recommend Mobil or Motorcraft. The synthetic fluid absorbs less moisture and can withstand higher temperatures, a good thing if you race your car.
    - For this procedure you will need the help of a friend to press the brake pedal while you open the bleeder valves on the brakes. You will also need to place a rubber hose on the bleeder at the brake to pour the old fluid inside a used bottle.
      - Start with the passenger side REAR caliper,
      - have someone press the brake (or use a jack against the seat and brake.) and open the bleeder slowly until fluid stops leaking, then close it.
      - Ask your buddy to remove his foot from the brake pedal or remove the jack.
      - Repeat this procedure 5 times.
      - Now check the fluid level and add NEW FLUID to the reservoir.
      - Go to the drivers side rear wheel, repeat the process.
      - Do the same at the front, go to the passenger side first then do the drivers side.
      - Don't forget to fill the brake fluid reservoir tank before it gets empty!!!.
      - Take the car for a spin at SLOW SPEED, and test the brakes several times, increase your speed as you get confident that everything is ok, hit the brakes harder and harder each time. If they feel very "mushy" or soft, try bleeding them again, probably a bit of air got into them.
  - 9. KEY-ON KEY-OFF / ENGINE-ON ENGINE-OFF TEST
    - A KOEO and KOER test will tell you a lot about the health of your car. Even if you haven't seen the CHECK ENGINE light Flash. And it is a procedure that is easy to perform with just a piece of wire or a digital voltmeter.
    - The complete EEC test procedure can be found on the "Trouble" page. After performing your tune up and checking your EEC for stored codes it is a wise idea to reset the EEC stored memory tables. When the tables get erased the EEC will start to relearn its fuel and air strategies which will make you car perform better. To erase the memory all you have to do is disconnect the battery for 20 minutes.
  - 10. FINAL COMMENTS
    - After performing this HI-PERF TUNE-UP your car will feel a lot stronger, your MPG will increase and your stang will be happy !
    - This complete tune-up should be performed once a year with the exception of some stuff like lubricants, filters and plugs that should be replaced every 3,000 miles.
    - Your wires should also last more than a year..so don't go replace them every year, but probably every 2-3 years.
    - Now..get out of here and enjoy your car!
    - Article from mustangforums.com

MAINTENANCE AND TUNEUP PART 2
- CLEANING YOUR IAC
  Well, in part 1 we skipped one of the MOST IMPORTANT aspects of a complete tune up. Your EEC relies on a number of sensors to gather information about several stuff such as Oxygen content in the exhaust, coolant and air temperatures, throttle position, more...
  - THIS INFORMATION IS USED BY...
    - The information is used by the EEC (PCM) to tune the delivery of fuel, air and spark. If any of those sensors fail for any reason, the EEC will instead relay on stored values in its memory to compensate for the loss of a sensor signal. This will trigger a FAULT CODE which will be displayed as a "check engine light" and a stored fault code number inside the EEC memory. Sensors can fail for a number of reasons: faulty connection, dirt in sensor or an actual hard fault (dead sensor). But in reality, the chances of a complete sensor failure are small, most of the time the failure is either a dirty connector, bad wiring or dirt in the sensor.
  - MAS SENSOR(MASS AIR SENSOR)
    - The MAF is one of the most important sensors in your engine, it is composed by 2 elements, the housing and the meter.
    - The housing is a 3"+ aluminum cylindrical element that sits inside the air filter housing.
    - On top of the housing sits the meter, it is a small black box that contains 2 thin heated wires (when on). Those wires change their resistance as air flow cools them down and the resulting voltage is sent to the EEC to tell it how much air is flowing, the EEC then will adjust injector pulse to change fuel delivery
    - One of the most common MAF failures is caused by DIRT that passed through the air filter. If you use a stock air filter, the time it would take for the sensor wires to gather enough dust to fail would be long. But in the case of aftermarket OILED filters such as a K&N it will take a short time if the filter is over-oiled.
    - So if you have a K&N that has been cleaned and re-oiled, let it sit for a while to let the excess oil drip, then clean it with a lint free cloth.
    - A contaminated MAF sensor can be diagnosed by several symptoms:
    - LEAN CONDITION - displayed as KOER codes from the O2 sensors
    - BACKED UP TIMING -
    - a result of the lean condition in which the EEC will back timing to reduce chance of detonation
    - LOW TOP END POWER - as a result of reduced timing and fuel.
    - So what can you do to remedy this?
    - The answer is simple, remove the MAF housing from the air box. At the top of it remove the 2 retaining tamper proof Torx Bit screws and GENTLY pull the sensor out. If the 2 filaments of the sensor are dirty (dark in color) clean them with a Qtip until all contaminants are removed. Check the Maf wiring harness for loose or dirty connectors and bad wiring.
    - Reinstall and test your car.
    - You will instantly feel a GREAT difference in horsepower, probably as much as 30hp are lost when the MAF fails by contamination.
  - O2 HEGO SENSORS(HEATED OXYGEN SENSOR)
    - This is another very important sensor, as it "reads" the amount of oxygen that's present in the exhaust. This information is sent to the EEC which then compensates the fuel accordingly.
      SN95 oxygen sensors are "pre heated" which means they will reach operating temperature faster than non heated ones which reduces emissions on engine start.
      Again, the most common cause of failure in an O2 sensor is contaminants, which are always present in the exhaust as carbon and probably unburned oil.
      The chances of O2 sensor hard failure are larger as the car gets older but in most cases they last lots of years, and with some precautions you can make them last a lot longer.
    - A bad 02 sensor will show several symptoms:
    - Rich or Lean fuel condition
    - O2 sensor fault codes 136, 137, 139, 144 and 171 through 178
    - Reduced HP
    - 5.0 engines have 2 heated sensors close the heater pre-cat, on 3.8 and 4.6 models there are 4 sensors located before and after the catalytic converters.
      
      To check the sensors first disconnect and inspect the wiring, remove the sensors and clean them, don't use any type of chemicals to do this, the cleaning should be done by using a PROPANE TORCH, place the sensor tip inside the propane flame for a few seconds at a time until all contaminants get evaporated by the heat. Place the sensors back in place.
  - ENGINE COOLANT TEMPERATURE SENSOR(ECT)
    - The ECT sensor is a thermistor, basically a resistor that changes voltage accordingly to temperature changes. It provides a reading that's used by the EEC to change fuel delivery at engine startup to reduce emissions and monitors the temperature of the engine.
    - Codes 116 to 118 indicate an ECT sensor problem or failure.
    - Remove the ECT sensor, on 5.0 engines it is located at the front passenger side of the lower intake manifold, on 4.6 engines it is located at the left side of the alternator outside the engine block.
    - If you see some rust in it clean it by sanding the surface using a fine grit sandpaper, Also check the connector and wiring. Reinstall and check for codes, if some are present change the unit.
  - INTAKE AIR TEMPERATURE SENSOR (ACT or IAT)
    - Also a thermistor the IAT sensor changes voltage accordingly to ambient air temperature.
    - The EEC uses this information mostly to change fuel delivery when the engine is cold at startup. The sensor is located inside the Intake air duct.
    - Codes 112 to 114 will set a IAT sensor code in the EEC.
    - If this occurs, remove and inspect the sensor it could get contaminated by engine oil , K&N oil or dust. Clean the sensor with isopropyl alcohol. If the sensor still fails replace the unit.
  - THROTTLE POSITION SENSOR (TPS)
    - If you haven't already read how to do it a million times in all of the Mustang magazines then this is your chance. Here's how to check and adjust your TPS voltage.
    - You may be asking, "What is a TPS"? Simply put its the Throttle Position Sensor. The TPS is a sensor that tells the ECM (computer) how much gas you are giving it, which in turn lets the computer decide how much fuel and spark to give you.
    - The TPS is located at the end of the throttle shaft on the throttle body. Using the TPS voltage signal the EEC determines fuel delivery based on throttle position.
    - A bad TPS can be the cause of bad idle, which is caused by the injector pulse fluctuating.
    - Some loss in performance can also be expected.
    - Codes 122 through 125 are present when the EEC detects a TPS problem.
    - Sensor Safe carb cleaner or TB cleaner can be used to clean the sensor. If the problem persist replace it.
    - Enjoy your stang and drive safely
      Another article from allfordmustangs.com

Solving Idle Problems

Clutch Replace

VIN Explained

Vehicle Certification Label Explained

Vehicle Certification
Label Explained