2003 Nissian Altima 2.5

Unlikely that the 50 psi fuel pressure is your problem, but if it is, it could be caused by a bad pressure regulator. I would first test for spark, then injector pulse using a "noid" light. Most common failure is no spark due to bad crank or cam sensor.

There are several thing that cause the engine to die. #1 Electrical Install a spark noid on plug wire this lights up as the plug gets it power if this signal is lost then test the crank shaft sensor L-6 engine located on drivers side of engine at transmission just to the left of master cylinder V-8 engines it is just behind the passenger cylinder head . #2 Fuel pump control test for fuel pressure at service port about 36 psi running and as you rev the engine it should go up 40-45 psi and when shut off it should retain pressure above 30 psi when dies check pressure loss of pressure could be due to fuel pump relay is bad #3 just the fuel pump is shutting off.

what rpm or speed, both? which Civic engine????? of the 5
and what country????? we can not guess this... ever.
and no one ever says.. here. 99% true.
why is not easy. 50ways there are.
it's running rich. (we have one good input. this)

but here are the reasons, (not the 50 causes) all the below are tests.
it's misfiring. is rich misfire.
causes: many I'll assume the cars 12v power is 10 to 145v at all times. 13.3v running minimum.
1: low compression on one or more cylinders. 150psi w.o.t is min.
2: bad spark or not timed right. to any cylinders. or all. tests.
3: bad fueling. above must be good (tools used and tests)

now if compression is good. and the EGR main down leak
if spark is good, what causes high HC,
simple misfire.
what causes misfire.

1. bad spark plugs (ever tune it up? now be the time, huh?)
2. bad injectors, leaking or clogged. clean em.
3. fuel pressure too high, 28 is min, max (see end)
4. you find one injector , NOID lamp test stuck ON.
5. o2 sensors stuck lean (exhaust leaks)
6. Fuel pump regulator stuck closed, causing #3

there are 5 engines, (why not state yours.??????0
1.5 L to 3.0L
the fuel pressure is different on all .
40-47 PSI. 1.7L and 2.3L
47-54 PSI on 2.0L and 2.2L
41-48 PSI on 3.0L
and then the exceptions
1-- Except SULEV: 48-55 psi SULEV: 47-54 2 Except SULEV: 47-55 psi SULEV: 48-55 psi
if you read the FSM,, it shows tests at the rail.
fuel pressure.
fuel regulation test.
shut test
injector leak down test.
and the injector balance test.
we do them all, or fail;.
all this is FSM.

do you want us to guess or test?
the latter avoids the 50 guesses. 49 being wrong.$$$$$$$$$$$$$

check fuel pressure TBI injection fuel pressure should be 9 - 13 psi.make sure fuel pressure above 10 psi because throttle body need at least 10 psi. in order to work right.if all is good check see if PCM firing the fuel injectors.go to auto parts store buy noid light.to use noid light you have to disconnect fuel injector electrical connector then plug noid light into fuel injector connector.crank engine watch noid light should blink meaning PCM is firing fuel injectors if noid light steady not blinking PCM not working.if noid light dont light up you have open circuit in the fuel injectors wiring.if check engine light flashing have vechicle code scan.bad tps sensor will also cause problem you are having.

when the engine is cool spray carb cleaner around the intake manifold

use a digital volt meter,put it on the ohm scale check number 2 fuel injector should be 11 to 16 ohms if not reads zero fuel injector faulty.if numbe 2 fuel injector okay.use noid light hook it to fuel injector electrical connector with fuel injector disconnected and see if pcm is firing the fuel injector noid light should blink when cranking the engine.if light steady pcm not firing 2 fuel injector,if noid light dont light up.there is a open in the wiring connector 2 fuel injector 2. if fuel injector okay,check spark plug, carbon foul you have a bad ignition coil or wire if you see oil on spark plug you have worn piston ring or leaking valve guides allowing oil to foul out spark plug.do a compression test check compression to see condition of the cylinder.

Spray starting fluid or carb cleaner into the air intake to see if it really is a fuel problem. If it tries to start, like firing for a few seconds, it is probably not getting gas to the cylinders. Then you need to check the injector circuit. If fuel is getting up to the engine, then the pump is working, but maybe not good enough-check that by testing the fuel pressure. Hook up a fuel pressure gauge to the fuel rail, turn key to on, and you should see high pressure on the gauge, about 50 psi, but check for manufacturer specs for the correct pressure.

The injector circuit uses a fuse for the injectors, then it applies constant voltage to the injectors when the key is in on or run or start. See if you have voltage to the injectors with the key on. The injectors will pulse when the pcm momentarily grounds the injector circuit-it grounds each individual injector internally inside the computer for a split second. This causes the injector solenoid to energize and raises a pintle inside the injector so that fuel under pressure will spray out into the cylinder.

what you need are two things....a set of injection noid lights and a fuel pressure guage. check the pressure at the rail (there might be a schrader port for this). If there is no pressure here inspect the fuel pump relay in the relay box. If you have around 40-45 psi at the rail once you cycle the key unplug the injectors one at a time and check for injector pulse.

MAKE SURE WIRES ARE GOOD, to check injector Get a noid light and take that injector plug and plug into noid light it should light up everytime injector would pulse.(IT SHOULD BE A STEADY PULSE) contact if you need more help

spark and fuel pressure at the times while it not starting? I hope so.
Will it start if you spray carb cleaner in the intake? If so we are dealing with an Injector issue Several injectors could be failing when hot It's very common also you need to hae a NOID light to verify that the injectors are being PULSED by the ECM if you have NOID and spark and fuel pressure then the only thing to do is while its stone cold. OHM all the fuel injectors and record all the reading for each cylinder.
Drive it then once it will not start, quickly do the ohms test again and record all readings again and any readings that are lower are likely bad injector windings and you need new injectors.
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