The Gotts Mod was originated by a member (Gotts2BMe) on the F150 forums. The original article can be found here. The concept was to cut off the small "snorkel" end of the factory airbox and replace it with a section of pvc pipe. The diameter of the pvc pipe was larger than the Ford snorkel, which allowed a greater amount of air to enter the intake. The parts were inexpensive and the mod was easy and effective. It became very popular for this model of Ford.
I own a 2010 Ford Expedition and the original Gotts Mod is not applicable because the air intake system is completely different. But, Ford continued the method of using a large airbox with a restrictive snorkel. And some rather smart people noticed that Ford continued to use the same airbox in later versions of their line-up, but significantly increased the snorkel size.
So, all you need to do is buy a snorkel from a later model Ford and install it on your factory airbox.
You are modifying your factory engine configuration. Even though you will be using factory Ford parts, this may void your warranty and violate various Federal, State, and Local environmental regulations. You will also be handling some delicate parts that, if broken, are expensive to replace. Proceed at your own risk.
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Step 1: Tools and Parts
Screwdriver - flathead
T20 Torx bit and driver
Mass Airflow Sensor Cleaner - $8 (any auto parts store)
High Flow Air Filter - $35 Spectre
Ford Snorkel P/N - 9F721- $7 Ebay or Local Ford Dealer(there are several different exact part numbers for this part as it fits various vehicles, but they all have the 9F721 in the part number. I used "AL3Z-9F721-A". Also, "7C3Z-9F721-A" will work.)
Step 2: Disconnect the Battery
We are not doing anything with the electrical system, but you do need to disconnect the battery. This will reset the computer and let it "forget" the current fuel mapping. The computer will relearn the fuel mapping based on the new, increased air flow. It will just reset the computer for fuel mapping. It will also erase your Trip Odometers, Average MPG, etc. This will NOT erase any of your radio presets or other functions stored in the car.
- Use the 5/16" socket/wrench to loosen the NEGATIVE battery terminal.
- Wiggle the terminal off and leave it disconnected for the install.
Step 3: Remove and Clean the Mass Air Flow Sensor
- Stat by loosening the band clamp and unhooking the Mass Air Flow (MAF) sensor.
- For the MAF sensor, there is a red locking tab on the bottom that you need to pull out (towards the radiator) first. Then the cable should pull off easily. *Remember to push the locking tab back in when you reinstall everything.
- Un-snap the 3 tabs on the air box lid
- Pull the airbox lid up and remove it completely.
- It pivots up as shown in the picture
- Remove the 2 screws holding in the MAF sensor with the T20 torx bit
- Slide the MAF sensor out.
- BE VERY CAREFUL WITH THE MAF SENSOR!
- THERE ARE VERY SMALL, DELICATE WIRES IN IT!
- IF THEY BREAK, THIS IS AN EXPENSIVE PIECE TO REPLACE!
- Lightly spray the components and area
- Let it dry
- Repeat a few times.
- DO NOT TOUCH THE WIRES!
- The goal is to clean off all the oil and dirt so that the sensor can get an accurate reading of the airflow into the engine.
Step 4: Remove the Air Filter and Airbox
- Pull the air filter out.
- inspect your air filter to see just how dirty it was.
- I goofed and pulled the airbox with the filter still in it, thinking it wouldn't be needed, but I had to remove it later.
- I started using a deep socket, but had to switch to a regular socket to get the back bolt out.
- You could remove the coolant overflow tube if you want, but it's not needed.
Step 5: Remove and Replace Snorkel
- Use the flat head screwdriver to pry/pop the small snorkel out from the inside of the airbox
- see green arrow in picture
- Compare the size difference between the small and large snorkel
- Push the large snorkel into place with your hand
Step 6: Reinstall Airbox and Air Filter
- Put the airbox back in place.
- Notice the two grommets/holes in the picture.
- There are 2 legs on the bottom of the airbox that need to be lined up and inserted into these grommets.
- use your fingers to feel and ensure there is nothing blocking the opening.
Step 7: Reverse the Procedures and Button Everything Up
- Reinstall the airbox lid.
- Clamp the 3 tabs back in place.
- Tighten the band clamp on the air intake tube.
- Plug in the MAF sensor.
- Make sure you push in the red locking tab after you install the plug.
- Reconnect the battery.
- Clean up the tools and everything else.
- Start the vehicle and let it idle for a few minutes just to make sure everything is good.
Step 8: A Week Later
If you have installed a new high performance air filter, it would be a good idea to remove and clean the MAF sensor again. The high performance air filters are an oiled cloth and that oil can sometimes coat/contaminate the MAF sensor after a fresh install. Cleaning the MAF sensor is an easy procedure and should be done every time you clean and re-oil your air filter. It is also recommended that you do this every 6 months, even if you are using the cheap paper filters. Keeping the sensor clean will help your engine computer accurately determine the amount of air coming in, which will let it accurately determine the proper fuel curve.
Step 9: Credits
This is not my idea. I'm not even the first to document the procedure on a Ford Expedition. But, it took me a while to locate the proper instructions on the forums, so I thought an Instructable would be easier for people to locate. The instructions and more information can be found here on the Expedition Forum. This mod should work on any Ford truck or suv with a similar airbox setup.