機械噴射引擎保養維修因為不像電子噴射引擎可以讀取故障碼，引此維修上就必須根據狀況來一一檢查零件的妥善性，才能排除問題，還好老車的關鍵零件就那幾個。
汽車故障維修對照表:
避免因為翻譯的錯意，特將車友"dudeperson3"的機噴維修心得原文引用(適用w126、w124、w201)資料來源：http://www.benzworld.org/forums/5378229-post1.html
If the Engine turns but won't start
1: No fuel pressure, or less than 50 PSI. Test the fuel pump (all 190s) and pre-pump (of those 190s that have two pumps) and do a fuel pressure and volume test.
2: Jammed and/or sticking airflow sensor. Remove the air cleaner and loosen the center line on fuel distributor. This will relieve the control pressure. Press down on the center of the plate and you should feel no resistance or binding.
3: Defective cold start injector. If the injector does not function, the air-fuel ratio will be lean, preventing easy start up...tho, it may still start.
4: Shorted or defective thermo time switch. The cold start injector will not work if the thermo time switch is defective. Check this in the event that your cold start injector does not function before replacing. (I personally was not aware of this, nor do I know where it is, but I trust them)
5: Control plunger sticking. Remove the fuel distributor from the airflow sensor and check to see if it moves freely. (I can't imagine this actually happening)
6: Restricted injectors. For this to be the cause, they would have to be severely restricted, which is why it is listed last. Do an injector flow test and ensure that the delivery is near equal.
Hot starting difficulty
1: Loss of rest pressure. Do a pressure test and focus on the rest pressure. If it does not pass, check for a defective fuel pump check
valve, defective (or clogged) fuel distributor, faulty system pressure regulator, and leaking cold start injector.
2: Airflow sensor adjusted incorrectly. Check height, centering and for binding. Remove the boot and loosen the center line on fuel distributor to
relieve control pressure.
3: Sticking or binding of the control plunger. Remove the fuel distributor and ensure that the control plunger moves freely.
4: Injectors leaking. Remove the injectors from the intake manifold and with the ignition key on and engine off, press on the center plate to pressurize the system. Inspect and replace any injector that is leaking.
5: Cold start injector leaking. Same test as above.
6: Shorted thermo time switch. Cold start injector is dependent of this component.
7: Incorrect control pressure. Do a pressure test and verify that the warm control pressure is within spec.
Rough idle (cold)
1: Cold control pressure incorrect. The movement of the control plunger will be limited if the cold control pressure is too high. This in turn will limit the amount of fuel able to be delivered through the injectors. The result will be a lean ratio and will cause rough idle.
2: Auxillary air valve defective. If defective and not opening, idle cannot rise and results in rough idle. (I think I have this issue in my 2.3)
3: Airflow sensor adjusted improperly or binding. If the movement is not smooth, it will result in air-fuel ratio errors. If you've never messed with it, and no one else has, then just check for binding or extra resistance (mechanical resistance).
4: Leaking cold start injector. If the cold start injector is leaking, the engine will be over-fueled even if cold. If the cold start injector is leaking, the idle will get worse as the engine temperature increases.
5: Injectors have an unequal flow or spray pattern. Do an injector flow test and replace any that do not deliver the correct amount of fuel or have a poor spray pattern.
Runs rough (warm)
1: Warm control pressure incorrect. Incorrect warm control pressure that is too high or low will cause an incorrect air-fuel ratio, thus resulting in a rough idle.
2: Airflow sensor adjusted improperly or binding. If the movement is not smooth, it will result in air-fuel ratio errors. Check for centering and correct rest height. (again, its more likely that its binding if no one has ever messed with it)
3: Leaking cold start valve. Again, will result in over-fueling the engine, resulting in a rough idle.
4: Injectors have an unequal flow or spray pattern. Do an injector flow test and replace any that do not deliver the correct amount of fuel or have a poor spray pattern.
Stalls after starting (warm)
1: Warm control pressure. If the warm control pressure is too high, the air-fuel ratio will be lean.
2: System pressure incorrect. If too high or low, the air-fuel ratio will be incorrect.
Idle speed high
1: Check auxiliary air valve. Ensure that it is closing. (Not quiet sure how to do that)
2: Vacuum leaks. Self explanatory, I hope. I'd start with the Air Flow meter and the boot below it, then all the connections on the intake manifold, and then the manifold/head connection. Also, all vacuum lines.
Backfire in intake
1: Check that CO adjustment is correct. If incorrect, backfire will result if started and under a load. (I'm not sure how to do that)
2: Boot between airflow sensor and throttle defective/leaking. Will result in a lean mixture due to extra air. Our cars are old, its rubber. It might have cracked.
3: Vacuum leaks. Self explanatory.
Misfires
1: Ignition. Inspect the cap, rotors, wires, and plugs.
2: Fuel delivery inadequate. Check for binding of airflow sensor, control plunger, incorrect control or system pressure and restricted injectors.
3: Injectors. Unequal delivery or poor spray pattern. Do a test and
replace any that are defective.
Poor power
1: Control pressure too high. If the control pressure is too high, the control plungers travel will be limited, resulting in a lean running engine.
2: Check ignition components. Verify that the spark plugs, wires, cap and rotor are not worn, dirty, or defective.
3: Injectors restricted. Do a test for delivery. If an injector is restricted, fuel delivery will be limited, thus power will suffer.
Sag or stumble when accelerating
1: Airflow sensor plate binding or sticking. If binding or sticking, fuel flow will be limited.
2: Control plunger binding or sticking. If binding or sticking, fuel flow will be limited.
3: System pressure or warm control pressure incorrect. If too high, the travel of the plunger will be limited.
4: Injector flow unequal. Self explanatory.
Fuel consumption high
1: Air-fuel ratio incorrect
2: Injectors leaking
3: Cold start injector leaking
燃油系統的重要零件
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