How to Clean Throttle Body and Idle Air Control Valve (IACV) on 4thgen Maxima

Member Credit: Cdg2125

Tools Required:

Ratchet
10m socket
12mm socket
Flathead or 8mm socket
Pliers or vise grips
1 can of Throttle Body cleaner
1 can of Carb cleaner (I find Berrymans B12 to work fastest)
New throttle body gasket
New IAC Valve Gasket (dealer only)

Step 1: Disconnect battery. unclip airbox, unplug MAF Sensor, use pliers to slide clamps holding hoses to airbox down and slide off hoses, use flathead or 8mm socket to loosen clamp holding air tube to throttle Body, remove 10mm socket on side of airbox holding it down and remove air intake assembly.

Step 2: Move the throttle to fully open position, lift throttle cables one at a time forward and wiggle out of the TB (towards the left of the TB). Unplug 2 Throttle Position Sensor Plugs.

Step 3: Remove the 4 12mm bolts holding the TB to the plenum

Step 4: On the bottom of the TB there will either be 2 or 3 hoses attached. use pliers to slide clamps down and remove hoses. make sure your radiator cap is still on or engine coolant will start to flow out. If hoses have seized on, use a flathead to pry the top and break the seal.

Step 5: Remove throttle body. scrape old gasket from both surfaces. clean entire butterfly plate (both faces) and cylinder. there should be no black when done. use only throttle body cleaner as carb cleaner will remove teflon coating which can later lead to faster corrosion and/or deposit formation

Step 6: Locate IAC Valve (triangular unit bolted to the driver’s side of the plenum right in front of the firewall with a large hose that was connected to the air intake assembly) unplug all 4 plugs.

Step 7: Remove 10mm bolt holding EGR Temp Sensor plug to the IAC Valve. (hard to see so you may have to feel around the firewall side for it) It is the only plug of the 4 not directly attached to the IAC Valve body

Step 8: Remove 3 12mm bolts holding IAC Valve to the plenum and remove IAC Valve. Remove old gasket (no need for scraping as it is a metal gasket).

Step 9: Spray/wipe the entire inside of the triangular face clean. Spray the inside of the brass housing clean of all deposits. spray base of Idle screw clean to ensure no carbon deposits remain. Be liberal with the spray.

Step 10: Replace gaskets and reassemble in reverse order. make sure when attaching the air tube to the TB you tighten the clamp. a loose clamp = a small vacuum leak that probably can’t be heard but will be felt (high idle).

Before reassembling, some like to spray remaining throttle body cleaner/carb cleaner into the plenum to clean it up. This is usually a waste of time since oil coming from the PCV will quickly muck it up again but pooled cleaner may help clean downstream intake when you start it back up. not enough to make a big difference but hey. If you do this, don’t be alarmed by the blue smoke at startup (oil and sludge being burned off). Start the car, take it for a short run to blow any remaining cleaner out and you are done.