1992 240sx stalling, rough idle

[Pisces0345]

One morning I went to start my 240 and it ran rough and would stall at stops; rpm's that normally would run at 800 at startup would now drop. I have read many of the threads about similar issues so I swapped the MAF, sprayed throttle cleaner in the IAA, added Seafoam to the gas tank. The car ran perfectly up until that morning.
The car still chugs, needs gas petal depressed at times to start, may run briefly and then die. I am at a loss of what is next on the list...motor shakes and almost suggests misfiring. After reading other comments about service techs shrugging their shoulders, I am hesitant to take it to the Nissan dealership for service. Read about coolant sensor etc.
What would be my next best approach with this issue??

Thanks for 'listening'.

[Pisces0345]

One morning I went to start my 240 and it ran rough and would stall at stops; rpm's that normally would run at 800 at startup would now drop to around 500. I have read many of the threads about similar issues so I cleaned and then swapped the MAF, sprayed throttle cleaner in the IAA, added Seafoam to the gas tank. The car ran perfectly up until that morning.
The car still chugs, needs gas petal depressed at times to start, may run briefly and then die. I am at a loss of what is next on the list...motor shakes and almost suggests misfiring. After reading other comments about service techs shrugging their shoulders, I am hesitant to take it to the Nissan dealership for service. Read about coolant sensor etc.
What would be my next best approach with this issue??
*** I disconnected the MAF and it ran smoother at 500; black smoke out of exhaust stopped; turned on AC, revs to 700/750.
Does this suggest the coolant sensor?? I am a couch mechanic and would appreciate any other suggestions, comments.

[centralcoaster33]

the *** tells you that your MAF is crapped out, nothing coolant about it. Which MAF? I don't know. Did both of yours make for a crumby idle and only when both were unplugged did things smooth out? Be sure to test wires before replacing a sensor. Coolant temp affects open and closed loop operation by the ECU. Get your FSM downloaded to a device for easy access. Look to the EC chapter. Check your car's computer for codes. Rough Idle can be tune up stuff, but you say it ran fun until one morning. So, I'm guessing one key component has become damaged or non-functional. A MAF is a key component. TPS, Vacuum leak, fuel pump, O2 sensors, etc. are things that could have failed. No codes for vacuum or fuel pump that I know. So check codes first, then check vacuum with pump or something, then check fuel pressure (or at least listen to the pump to see if you hear it start up when you turn the key on).

[PapaSmurf2k3]

If it gets better when you push the gas, its probably not MAF related, although don't rule it out. Look hard for vacuum leaks and bad idle air control valve.

[Pisces0345]

I disconnected Oxygen sensor and car started but the engine literally shook itself and the car and made a clanging sound , black smoke still from tailpipe. Reconnected the sensor, car will, start w/o pumping gas pedal(progress??) but with milder shakes and with black smoke from tailpipe.

[Lord Umoja]

Check Intake tract for leaks. My car has a crappy long tube cold air intake and sometimes develops leaks after the MAF. The car will stumble and die unless the gas is fully depressed. Also get some noid lights and check your fuel injector function. My car stared running a cylinder down and it turned out to be a break in the harness.