Nissan Repair: 2001 Nissan Sentra(1.8L) wont idle, throttle position sensor, air control valve

Question
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Followup To
Question -
This just started a few hours ago.  The car won't idle on its own(in any gear), but it will run if you depress the gas pedal.  No check engine light, but took it to Autozone anyway, no codes stored.  I'm pretty sure the problem is in the idle circuit, though I don't know which part could be bad.  The car has 90k miles on it. The crank position sensor was changed about 40k miles ago.
Answer -
Jason,

Make sure that you do not have a leak in the intake.  If the engine gets too much air at idle the computer cannot compensate and this will cause the car to die.  Also, check to see that the throttle body is clean and not black with carbon crud.  Lastly, make sure the idle air control valve is working properly along with the throttle position sensor.


The car starts fine when its cold, but after its warmed up, then it stalls.  How would I go about checking the idle air control valve and the throttle position sensor, and where are they located on this engine.  I can't find any manuals that deal with this engine.

Answer
Jason,

OK, now we are narrowing it down.  If the car starts fine when it is cold then you have a problem with the fuel injection system when the engine is at operating temperature.  So, when the computer reads that the engine is warm then it starts to stall.  There are a few things that can cause this.  My bet is going to be with the fuel injection system and fuel pressure to be precise.  Check to see if the fuel system has sufficient pressure.  If you go to Nisssan USA you can download the factory service manual on .pdf reader.  I would get the section that deals with the fuel pressure.  I think the engine is not getting enough fuel pressure when it is warm.  When you are in cold start mode the engine is over rich to compensate for it being cold.  When the computer reads that it is at temperature it cuts back on fuel use.  Find the fuel rail on the engine and disconnect the vacuum line to the fuel pressure regulator and see if the engine runs fine.  If it does you have found your problem.  I would be looking at a new fuel pressure regulator and filter and since these are all on the same assembly and in the fuel tank you will be changing it out as an assembly.