Cleaning Your Throttle Body and MAF
By: Bob_98SR5
Date: October 7, 2007

Part Needed

Tools/Supplies Needed
10mm and 12 sockets with extensions
Philips Screwdriver
Throttle Body cleaner
Electrical contact cleaner
Tooth brush (2 is good)
Cloth shop towels

I am providing this write up for illustrative purposes only. Perform at your own risk. Any mods (including this one) you perform on your vehicle is your responsibility. Furthermore, commercial use of this write up is prohibited---all images and text are property of Linking or copying any portion of this write up will result in legal action.

The purpose is to clean out any carbon deposits out of your throttle body for a better off-the-line response. In addition, for those of you who run oil-based foam filters like K&N, Amsoil or Tru Flow, this is a good maintenance task to perform if you find your throttle response a little sluggish because of over oiling.

Step 1: Removing the Air Intake Tube and Air Filter Box

Begin by removing the air intake tube by removing various hoses and screws. At the top of the intake tube that attaches to the throttle body itself, remove the large vaccuum tube as well as unscrewing the clamp screws as pictured below. Moving downwards, unscrew the clamp screw near the MAF unit, unhook the MAF harness, and remove the hose leading into the airbox.
You can now remove the air intake tube as well as the air box.


Pull out vaccuum tube (V) and unscrew screw (S)

    Unscrew bolt (S). This is a MAF unit from a 98 4Runner. The 99 MAF unit is nearly identical in appearance. Unbolt harness (M), remove the two bolts below it, pull hose (H) out and unbolt the three 12mm bolts from the air box

Note: If you are careful enough, you may not need to unbolt the air box to remove the MAF unit. However, unbolting the MAF unit's screws on a 99 may be tricky and you run the risk of stripping and dropping those tiny screws into your engine bay. Thus, I removed the air box. Here's a pic of the 99 MAF unit (courtesy MTL_4Runner):


Step 2: Manipulating the Throttle Body for Cleaning

To open the plate, press down on the throttle body lever as shown below. You need to hold this open while you clean out the carbon deposits:


Press down on the throttle body lever to open the throttle body plate.  

After removing the parts, look into your throttle body. You should see a carbon buildup around the edges of the throttle body plate. This is what you want to clean out.

Here's the plate in the closed position with the carbon build up around the edges   Yes, it gets that dirty. Clean this out!

The best method I found was to spray your carb cleaner in there and let it sit there for about 20 to 30 seconds. Then using a toothbrush, scrub the carbon loose. Spray again and let it sit for about 10 to 15 seconds and then take a shop rag and wipe out the inside. It will be black. You may need to repeat this process a few times to get it clean.

Step 3A: Cleaning the 96- 98 MAF Sensor
For 96 to 98 4Runner owners, the MAF cleaning is a bit ambiguous. You can remove the MAF sensor unit itself and spray electrical cleaner into it, but it is not obvious by looking if anything is being cleaned or not. Begin by removing the MAF sensor itself by unscrewing the 2 bolts from the MAF unit.

Remove MAF sensing unit M by unscrewing screws (S). Use a delicate touch here.   Spray into the large hole

Step 3B: Cleaning the 99- 02 MAF Sensor
99 and onwards MAF wires and sensing unit are easily accessible. To remove the sensing unit, use a philips screw driver to remove the screws. Note: the screws are threaded into plastic, so when unscrewing and re-screwing, do not exert too much force or over tighten. Remove the MAF sensing unit and spray the inner MAF wires with electrical contact cleaner and spray the large ring with carb cleaner. Reassemble when you are finished.

CAUTION: those little MAF wires are VERY, VERY delicate. I've read a few posts over the years where people wiped them with a shop rag or a Q-tip and the wires snapped. If that happens, you have to buy a new MAF sensing unit...which usually means that you have to buy the whole darn thing. They are NOT cheap. Thus, I just spray it a few times with the electrical cleaner and let the chemicals do the work.

Remove MAF sensing unit M by unscrewing screws (S). Use a delicate touch here.   Clean wires (W) and spray into the large hole as well

Re-assemble everything in reverse order.

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