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You need to do a fuel pressure leakdown test, start the engine and make sure the test gage that you hooked up to the fuel injection rail test port is not leaking, then turn off the engine, you should not see any more than 5 PSI drop in pressure. The other possibility is that you have carbon deposits on the intake valves or other related wear issue with the engine. Does it burn alot of oil?
The fact that it will start with the throttle body cleaner means that the PCM is attempting to start the engine. The fact that there is fuel at the rail and there is pressure may be misleading. There may not be ENOUGH pressure at the rail to do the job. Check the fuel pressure regulator....pull the vacuum line off the regulator. If there is any fuel in the line, the regulator is faulty and must be replaced. This is the most likely candidate.
Sounds like loss of fuel pressure on the injector rails when the engine is turned off. It is taking a while for the pressure to build up so it will start. This is usually caused by a bad check valve in the fuel pump (which requires a fuel pump module to fix) or a defective fuel pressure regulator or a leaking injector.
To see if loss of fuel pressure after shut-down is the problem, shut it off and leave it off as long as you usually do. Then, when you get into the vehicle, "cycle" the ignition switch a few times from OFF to ON, then OFF and ON again - repeat 3 or 4 times (Pre-charge the fuel rails).....THEN crank the engine. If it starts right up, then you know for sure that is WHAT the problem is, then you only have to find the CAUSE.
It sounds like you may have a couple different problems here.
Firts, the stalling when coming to a stop problem is MOST LIKELY being caused by a bad Idle AIr Control (IAC). The 4.6L engines are known for these "sticking" and working intermittently.
As for determining if the fuel pump is bad, the fuel delivery system goes like this:
Connect a fuel pressure gauge to the service port on the engine fuel rail. Cycle the ignition switch from OFF to ON. Repeat at least 3 times to obtain the highest reading.
The "Key-On-Engine-Off" fuel pressure specification is 35 to 45 Psi.
The fuel pressure should remain within specifications for at least 3 minutes after the key has been turned on. (the pressure will probably jump to 50 to 55 psi when the key is first turned on, then drop to within the specification in about 2 seconds after initial fuel rail priming has occured.)
If this is all good, your fuel pump and the rest of your fuel delivery system is good.
If the pressure does not reach the specified pressure or does not hold the pressure for 3 minutes, let me know and we will check further for the cause.
pressure loss is either a bad fuel pressure regulator on the fuel rail where the injectors are, or a bad check valve in the fuel pump in the tank. usually the latter.
A quick test is to turn the key to on and measure pressure. Should be 40 psi. Pump will hum for 5 seconds and shut off if engine is not running. (Safety step).
Pressure should drop very little for 5 minutes.
You can cycle the key off for 15 seconds or until you hear the relay click off. Then turn key back on to start pump for 5 seconds again to build pressure. This will help get it started for the day as it builds pressure that bled down over night.
You need a new fuel pump relay. The engine fires up and runs off the oil pressure switch untill the oil pressure PSI is reached at normal operating conditions. When the oil pressure reaches its operating PSI the PCM or engines computer will shut off that circuit and turns on the fuel pump relay to run the fuel pump untill you shut the engine off
Check the fuel pressure at the shredder valve, there should be 62 to 65 PSI when the ignition key is turned to the run position. (engine not running) Once the engine starts and is running, it should drop about 5 PSI. If the pressure is less then 62 PSI when the fuel line is pressurized, the engine will not start. If the pressure is good, then you may have a bad fuel Injection system which is a common problem to the CPI. Good luck and keep me posted.