1996 Nissan Maxima • 150,000 miles

Hi everyone
I have nissan maxima 1996. I got a problem.

strong smell comes from inside the hood after driving and facing very bad gas milage.

engine stall on neutral and sudden jerk (or loss of power ) when accelerating.
sudden change in RPM position when neutral. Sometime high RPM till 1500 and sometime decrease till 300 and black smoke from exhaust and engine die after RPM get low.

note - I disconnected TPS when engine running but no changes. I done same with the idle air control valve and no changes in idle.
July 20, 2013.

If there are no changes when you disconnect the sensors, you need to check if they are working. It doesn't sound like it. As far as the black smoke, that comes from a rich fuel mixture which will smell and cause more fuel consumption. The question is, what is causing it to run rich. Has the check engine light come on? Have you checked to see if the fuel pressure regulator is working?

No check light is there
And I didn't check fuel pressure regulator. Where it is located?

Jul 20, 2013.
The regulator is located on the fuel rail. If you go to our homepage under the DIY section, there are directions and a video for checking fuel pump pressure which includes checking the regulator.

I want to tell u something
Yesterday I noticed petrol leaked from somewhere and collected under the intake manifold in between the engine and the smell is coming from there only but no traces found on injectors or on fuel regulator.

Jul 21, 2013.
Do this, either check to see if you can spot a leak with the engine running, or check fuel pump pressure to see if it is within spec. Also, when checking the pressure, pay attention to fuel pressure drop off. That is when you shut the key. The fuel pressure should maintain for several minuets. If it drops very quickly to 0psi, you have a leak somewhere.

Let me know what you find.