Do it at your own risk!
照例，抄袭网络介绍：From autorepair.about.com
In a fuel-injected car, air is drawn in through the air intake. This is usually a long plastic tube going into the air filter housing. The reason the intake tube is long is to get the air moving in a fairly steady, coherent stream. It then passes through the air filter and then through an Air Flow Meter.
There are two types of AFM's, a vane type and a hot wire type. The vane type has a flap that is pushed by the income air. The more air coming in, the more the flap is pushed backed. There is a potentiometer attached to the flap that sends a voltage signal to the Powertrain Control Module (PCM). There is also a second vane behind the main vane that fits into a closed camber that dampens the movement of the vane giving a more accurate measurement. There is also an Air Temperature Sensor built into the AFM and works exactly as it did in the carbureted engine.
The hot wire AFM uses a series of wires strung in the air stream. The resistance of the wire at normal operating temperature is a known constant and will allow a set voltage through it. As the air passes the hot wire, it cools. As it cools, the resistance of the wire decreases allowing more voltage to pass through it. This voltage signal then goes to the main EFI computer and allows the adjustment of the fuel mixture. From the AFM it goes to the throttle chamber.
The throttle chamber controls the airflow into the engine. When it's closed, the car idles. There is a small bypass chamber that allows a small amount of air to bypass the throttle plate and go into the engine. By adjusting the amount of air through the bypass, we can adjust the idle speed of the engine. There is also a Throttle Position Sensor (TPS) mounted on the throttle plate that sends a signal to the main EFI computer telling it weather it is at idle, midrange cruising or wide open throttle. From the throttle chamber it goes through the intake manifold and into the cylinders.
One last component is the Cold Start Valve. It is electrically heated and performs the same function as the choke on a carburetor. The Cold Start Valve is a valve with a bi-metallic element that expands as it's heated. When it's cold, it allows a large quantity of air to bypass the throttle plate thus causing an increase in idle speed. As the element heats up, it closes the bypass passage and lowers the idle speed as the engine obtains normal operating temperature.
总而言之，言而总之，汽车air intake就是负责吸入新鲜空气，提供给发动机燃烧汽油。
四大部件：air filter, mass air flow sensor(MAF) or air flow meter(AFM), throttle body, 和idle air control(IAC).
其他还有不少小玩意，俺就不在这里露怯了。IAC 在我另一篇里单独介绍，所以这里只涉及三大部件。
打开车前盖，大多有这么一根粗大无比的长塑料筒子，这东西上下前后连着的东西加在一起，就是你的air intake system.
Throttle body, 你的气门，就是油门。一根钢缆控制气门开关大小。你脚踩油门踏板，就在拉动这跟缆绳，控制气门大小。所以，今后不要说踩油门，加油。应该是踩气门，加气，OK~~ 哈哈
粗塑料管子两端的螺丝卡子松开，两头就都拔出来。连接原理跟烘干机的排气管道一样。大管子上还连着几根小管子，都拔下来，如果怕搞错，就标记好。Throttle 上的电路可以断开。如果不把Throttle 整体卸下来，那也可以不动电路。MAF最好拆下来清洗，所以电路断开。
用手旋转缆绳结构，打开throttle风门，里边看到黑乎乎的碳沉积和污垢。我的不算太脏。相对这么粗的管道，我怀疑这样一点污垢是否能影响功能。请老大们指点。
另外一端，看进去，管道中间伸出来的就是MAF sensor,线路结构在管道上边。再里边，可以看到intake的air filter.
需要这些清洗剂，对号入座，不要搞错。
Throttle拆下来可以清洗的彻底些。我的感觉不够脏，懒得再拆，就翻开风门，直接大量喷throttle cleaner.我的车throttle安装角度刚好合适，清洗剂和污垢正好流出来，不会倒流进去。下边要多垫些布，不要让清洗剂污染其他车内部件，尤其是皮带。几乎用完一整罐throttle cleaner，流出来的都是铁锈色的污垢。网上见过有人用2罐洗一个throttle的。
流出来的清洗剂基本无色以后，停止喷洗。敞开风门晾干。
拆另一侧的MAF.需要特殊的socket set. 又忘记英文名称了，反正汽车零件商店里不难找。注意同样是星状socket，这个中间还要带一个窟窿。有些是没有窟窿地。此地停工15分钟，去商店15刀砍一套新socket回家。
MAF螺丝拧开，拿下。用对应的cleaner狂喷一通。
下边是一个简单而重要的部件 --- air filter. 这个东西堵塞不畅，直接影响你发动机喘气，会很无力地。一般filter藏在塑料盒子里，盒子的固定锁很像一般工具箱的挂扣，打开很简单。
打开塑料盒子。有些车，什么东西都不需要拆，直接就可以松卡子翻开换filter.
Filter正面，看不出啥
Filter反过来，跟新的比较。记住，air filter对发动机影响很大，也容易污染堵塞，所以应该经常检查和及时更换。
Filter盒子底部也很多油泥污垢
平头螺丝刀从盒子底上刮出来的污垢
老办法，吸尘器，加一层擦手纸
刮松动filter盒子里所有污垢，然后，我吸！
清理好，装上新filter.
盖子扣回去
MAF插回去装好
螺丝拧紧
检查清洗剂污染。有一点点，尽量擦干净。皮带和飞轮上都没有
所有管道连接安装回去
我的air filter相对最脏，问题最严重，更换以后，发动机声音和反应都得到明显改善。
将来的想法是下边这个酷东东。一个比较好的改装kit 也就$150-200，相当于换不到10次普通filter价钱。这种up grade filter是life time use不用换。如果我还能开个3-5万迈，这个东东应该非常合算，可以改进发动机表现和减少油耗，开的再久还可以节省air filter 价钱。不过据说这种cone filter有干/湿两种，不知哪种类型合适，那个品牌较好。另外，据说上边吸气痛快了，下边exhaust也要相应加粗，不知道是不是必需。请有经验的高人们指点一二。谢谢。
Update: 通过请教，换大流量filter的念头打消了
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