My nissan altima 2000 hesitates at low rpm, i changed the plugs rotor wires and cap all the fluids, the radiator fan stop running too, so i changed the relay and it works fine now, but the car still hesitates at about 500 rpm, another thread stated a fact about the mass air flow sensor, how do i know if it is that and not the injectors, or fuel pump. Would it be advisable to have a pro diagnosis my car with a scan tool and then determine wheater the work should be done in the backyard, help please, my wife is about to kill me

You can have the codes accessed for free at AutoZone. If the service eng light isn't on, there are not any codes stored. The fuel pump test is, connect a pressure guage and read the pressure. Fuel pressure should be about 28-33 psi. You have an electric fuel pump that supplies constant fuel pressure regardless of RPM or anything else. One thing that changes as you begin to accellerate is the fuel pressure regulator will increase fuel pressure 3-4 psi. There should be manifold vacuum at the hose that connects to the FPR when the engine is idleing. Whe manifold vacuum decreases, fuel pressure increases. Tap on the MAFS while the engine is idleing. There should be no change in the idle or cause missfire or rough idle. The MAFS is connected to the air filter box. Injectors are seldom a problem and not likely to cause a hesitation. Check for disconnected or cracked vacuum hoses. Relays go bad, bad grounds and low battery voltage cause them to deteriorate sooner. Clean the battery cables. Idle speed is 650 RPM. When is your engine running at 500 RPM? As for your wife, wash her feet and paint her toe nails. You can buy everything you need at the dollar store. She may fall over dead and you can always use the wash tub next time you change oil.

thank very much you've been a big help,not only does the comic relief help with the stress but you have given me a list of things do. such things that do not correlate with bills or work or anything that won't make me forget about the world and it's lovable and hateful burdens.
gracias my friend muchas gracias.