Service engine light on…car hesitates/stalls after stop

2001 BUICK LE SABRE….service engine light…car misfires…whirring noise after i cranking up the car which is sometimes louder during acceleration…car hesitates after stopping& trying to accelerate…replaced spark plugs, spark plug wires, EGR valve, catalytic converter…error code says something about insufficient vacuum EGR valve…i was thinking replace MAP sensor but what could the problem be?

My car has 150000 miles.
My car has an automatic transmission.

Experienced mechanics share their insights in answering this question :
The EGR valve is a small component designed to allow the flow of exhaust gases into the intake manifold in controlled amounts. As such, it’s a simple valve that closes and opens as needed. The EGR valve has one single job to do, regardless of the system configuration, type of control and number of sensors: that is, to either open and direct exhaust gases into the combustion chamber, or to close and keep them from entering. Whenever you start the engine, the valve comes alive and waits in a closed position, blocking the flow of exhaust gases. Once the engine reaches operating temperature and speed increases, the valve, either through vacuum or electronic control will gradually open, allowing burned exhaust gases to enter and combine with the air-fuel mixture inside the combustion chamber. If you slow down sufficiently or come to a stop, the valve gradually closes and blocks the flow of exhaust gasses. After you shut off the engine, the EGR valve closes and remains in that position. When the EGR valve is clogged or dirty, as they are prone to, it may not function properly causing the engine idle rough, stall at idle speeds, cause the car to get poor fuel mileage, emit a strong smell of fuel due to excess hydrocarbons which also results in failing emissions tests. I would recommend having a professional from Your Mechanic come to your location to properly diagnose and repair your EGR Valve.

How to Identify and Fix Common car Problems ?

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Check engine light: as with most engine management components, a problem with the EGR valve may trigger the check engine light. Engine performance issues: if the valve is stuck open the vehicle`s air-fuel ratio will be disrupted causing engine performance issues such as reduced power, poor acceleration and rough idle.
One of the most common causes of engine misfires is a faulty EGR valve. The EGR valve is responsible for recirculating exhaust gases back into the combustion chamber. This helps to reduce emissions and improve fuel efficiency. However, if the EGR valve becomes clogged or damaged, it can cause an engine misfire.
It can cause hard starting or in EFI cars it could cause a starting & stalling problem because it will give symptoms of an air leak past the mass airflow sensor,the EGR valve should be closed when the engine is first started & cold otherwise hard starting & driveability problems may arise such as flat spotting & …
If the EGR valve fails to open or close, the engine warning light will illuminate on the dashboard. A strong odour of fuel smelt from inside the vehicle is also a sign of a failing EGR valve as more hydrocarbons will be emitted through the exhaust due to the increase in fuel consumption.
A clogged or malfunctioning EGR valve can disrupt the vehicle`s air-fuel ratio, which can cause engine performance issues such as a reduction in power and fuel efficiency. The vehicle may also stall or hesitate while accelerating.
A faulty EGR valve can cause problems with the flow and operation of the EGR system leading to performance issues including a reduction in power, reduced acceleration and decreased fuel efficiency. It can also cause vehicle emissions to increase.
Due to oil in the intake air, carbon deposits or carbon fouling are caused which eventually the force of the valve can no longer cope with ñ the EGR valve can then no longer open, or it remains in its open position. This results in jerking, irregular idling or insuffi cient engine power.
The failures are usually caused by a build-up of deposits in the EGR valve over a period of time that causes them to stick. This build-up is part of the ordinary operation of the vehicle and should be regarded as a serviceable item requiring repair or replacement.
If your EGR valve gets stuck in the closed position, then this can lead to a build up of heat within the engine, which can cause the air fuel mix to ignite prematurely. This early combustion, which will be especially noticeable at low revs, is likely to create a knocking sound.
Car care experts recommend cleaning your car`s EGR valve after driving 45,000 to 50,000 miles to maintain it better.
Diagnostic trouble code (DTC) P0401 stands for “Exhaust Gas Recirculation (EGR) Flow Insufficient Detected.” This code means that the computer detects insufficient exhaust gas recirculation (EGR) flow in the system.
Will deleting my EGR cooler set my Check Engine Light? In some cases, yes. Installing an EGR delete on 2006 and up 6.0L trucks WILL result in the check engine light.

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