Your Throttle Body and MAF
10mm and 12 sockets with extensions
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 4Runners.org. Linking or copying any portion of this write up will result in legal action.
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.
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):
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.
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.
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.
everything in reverse order.