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I can think of a few thing's that could cause this , a mass air flow sensor, crankshaft position sensor , coolant temp sensor. If the check engine light comes on there should be a DTC - diagnostic trouble code stored in the PCM - engine computer ! I'd find a parts that will check for codes an go from there . unless you have a factory scan tool that will check engine data parameters !
DEFINITION: Engine cranks OK, but does not start for a long time. Does eventually run, or may start but immediately dies.
• Refer to Important Preliminary Checks Before Starting in Symptoms - Engine Controls .
• Search for bulletins.
• Inspect the engine coolant temperature (ECT) sensor for being shifted in value. Install the scan tool and compare the displayed engine coolant temperature with the intake air temperature on a cold engine. Check the resistance of the ECT sensor if the engine coolant temperature is not within ±3°C (5°F) of intake air temperature (IAT). Refer to Temperature Versus Resistance . If the ECT sensor resistance is not within the specification, refer to DTC P0117 or DTC P0118 .
• Inspect the mass air flow (MAF) sensor and connections.
• Inspect the operation of the idle air control (IAC) valve. Refer to Idle Air Control (IAC) System Diagnosis
• Using the scan tool, monitor the throttle position (TP) sensor voltage. The TP sensor voltage should be less than 0.9 volts with a closed throttle. If the TP sensor voltage is more than 0.9 volts, inspect the throttle body and accelerator cables for binding.
• Inspect for the proper operation of the exhaust gas recirculation (EGR) system. Refer to Exhaust Gas Recirculation (EGR) System Description
• Inspect the operation of the fuel pump. The pump should turn ON for approximately 2 seconds when the ignition is turned ON. Refer to Fuel Pump Electrical Circuit Diagnosis
• Inspect for incorrect fuel pressure. Refer to Fuel System Diagnosis .
• Inspect the fuel injectors and related fuses. Refer to Fuel Injector Solenoid Coil Test , and Fuel Injector Balance Test with Tech 2 or Fuel Injector Balance Test with Special Tool .
• Test for fuel contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
• Inspect the operation of crankshaft position (CKP) sensors A and B.
• Test for proper ignition voltage output using the J 26792 Spark Tester .
• Inspect for damaged ignition coils within the ignition coil module assemblies.
• Inspect for damaged or misaligned spark plug boots.
• Inspect for a missing or damaged ignition module ground spring.
• Inspect the spark plugs. Refer to Spark Plug Inspection .
• Excessive oil in combustion chamber-leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical 4.6L.
• Inspect for low cylinder compression. Refer to Engine Compression Test in Engine Mechanical 4.6L.
• Inspect the following for incorrect or damaged basic engine parts:
- Cylinder heads
- Camshaft and valve train components
- Pistons, and piston assemblies
There's a shutter valve to restrict air flow either before or after the air filter housing. In cold winter, this valve is closed as you start up the engine. As the engine area warms up, the shutter valve opens up to allow more air to flow into the intake manifold. In close position, the restriction in air flow results in rich fuel mixture. When its open, the fuel mixture is leaner. If it were locked in open position, you crank the cold engine and you get a lean mixture instead of a rich mixture to start up in cold mornings.
veral but my first thought was a leaky injector or fuel pressure regulator.
here is some detailed info, here goes.......
During engine operation, the fuel system is maintaining the required fuel pressure to meet the demand of the engine. When the engine is shut off , the fuel system should be at or near the same pressure level. The rate at which the fuel pressure drops can be an indication of an internal system leak (assuming no external leaking occurs) you don't have this as it would take only hrs to have a start problem.
Two most common areas of concern are the fuel injector nozzles and the pressure regulator. If the regulator valve has a poor seal, fuel will leak past the valve seat area and, since the pump is no longer running, pressure will quickly drop off or sometimes slowly. The causes for this could be a worn valve, weak spring or defective diaphragm. An internally leaking regulator can cause long crank times as it takes the pump longer to build pressure in the system.
The other potential problem area could be the fuel injector nozzles. The nozzle may be leaking due to a deposit build up on the nozzle or a worn out internal valve seat. In this case, fuel leaks directly into the engine's cylinder. Depending on the number of injectors on the engine, this could be a real problem if more than one injector is leaking fuel into the cylinders. This is a common cause of long crank times and hard starts after a short engine shut down.
One leaking and takes days to leak down.
Personally I'd start with replacing the fuel pressure regulator. Finding a leaky injector..try this. turn the key to the on position wait 5 minutes look at the injectors see if there is one that looks wet or has deposits around it.
You can also do a sniff test (not while running!) sometimes you can get a smell of gas from the leaking injector. (if the wind isn't blowing) Actually try this first before replacing fuel pressure regulator. If it starts up quicker after the 5 minute key on one of the above is the answer.
hope i didn't confuse you.
Best of luck.
Stay warm tis -5f here.
The best is to turn the key on to the run position for a few seconds then back off then back to run and then start. This cycles the fuel pump and sends a good supply of fuel up to the injectors. Also do not rev the engine excessively until it has warmed up to allow oil to flow good.
Good luck, dont forget to rate.
You will not see any vacuum from the egr solenoid until the engine has reached normal operating temperature and certain other driving conditions have been reached (like throttle position and road speed).
If the engine runs rough when warmed up, check the CTS (coolant Temp sensor) when hot and cold and if no fault shows there, start checking input sensors for engine and cam position, engine timing, RPM etc.
If the EGR valve was leaking, it is only adding air to the exhaust stream and usually, manually opening the valve and blowing out the seat with compressed air should fix the issue.
This can also be an issue with clogged injectors. When the engine is cold, fuel enrichment supplies more then normal fuel amounts to encourage even running. When the engine warms up (normal operating temperature), fuel enrichment mode is turned off. If your injectors are clogged (even if only slightly) fuel starvation will cause rough running. Fuel enrichment overcomes the starvation of clogged injectors. Try adding a propriety injector cleaner to your fuel tank and watch for an improvement. If you do see an improvement, have your injectors cleaned and tested professionally. If you locate any other issues with engine sensors, replace them and ensure the new components are adjusted correctly if required..
Pumping the pedal on an injected engine does nothing, except varying the air intake amount. I would change the fuel filter (if badly plugged, it may be causing the pump to shut off early) and clean the idle air control valve.(which should regulate idle air flow, eliminating the need for playing with the pedal) The valve itself is not difficult to service, but is a bit delicate. It can be cleaned with carb cleaner. just make sure you do not turn the valve end around while cleaning, and re-install it perfectly straight. You may have a bad drain back valve in the pump, but this is less common than what I outlined above.(there are tests for this)