Chevrolet Repair: 2000 Malibu Unusual Starting Poblem, fuel pressure regulator, valve plugs

Question
In my research on this and other websites a faulty fuel pressure regulator gave the same indication in two cases and replacement corrected the problem.  I was ready to latch onto that explanation, but I was having trouble understanding how a faulty fuel pressure regulator would cause those problems only when the engine was hot.  Can you offer an explanation?
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Followup To
Question -
Vehicle info:  2000 Malibu, automatic, 3.1L engine.

When engine is cold it starts fine and operates well.  Starting problem shows up when trying to restart the engine when it is still hot.  It then has trouble starting and if it does start it runs very roughly, then putting it in gear will make it stall out.  After engine cools enough it will restart without any problems and run fine.  As long as you don't shut off the engine it will then run normally.  Once when I put the AC on during normal operation the RPM would not go above about 2500 RPM.

The following things have been replaced within the past 6 months:
Fuel Pump
Fuel Filter
EGR Valve
Plugs

Answer -
There are numerous possibilities that can cause this problem and you will need to use a SCANNER in order to perform the tests required to resolve this fault.

Answer
That is one of the tests that would have been performed bsaed on the results of the scanner results.

OK, When the engine is COLD the TEMPERATURE SENSOR sends a signal to the computer of which holds OPEN the fuel injectors in order to emit fuel into the engine cylinders.

As the temp sensor warms up the amount of fuel being emitted into the cylinders is lessened and with a faulty pressure regulator you were not getting sufficient fuel rail PRESSURE or FUEL VOLUME due to the leak in the diaphram of the regulator thus causing insufficient fuel to be emitted into the cylinders.

I hope this helps answer your question and you were extremly lucky in guessing that the pressure regulator was faulty as this is not a common faulty component.

But I am glad that you did resolve your problem. NICE JOB.


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