Sunday, November 20, 2011

Exhaust gas recirculation flow?What does it mean?

I went to my local Auto Zone to get a alternator since I was told that might be the reason why my car stops cranking up at all unless I get jumped off. However, while I was there I let them do a diagnostic test on my car to find out why my Service Engine Soon light has been on for the past few months. This is what the diagnostic found out verbatim:





Troubleshooting P1401


OEM Brand: General Motors





Exhaust gas recirculation flow test fault


Explanation


The ECM performed an EGR flow test while monitoring the MAP sensor and detected low or no change.


Probable cause


-Check EGR valve function


-Check intake manifold for carbon blockage





What does all the mean in laymans terms lol, and what should I do to fix it?





Notes:


My car is a used 1999 Mercury Sable. Have had it for seven months. Has 15,980 miles still on it.|||the EGR valve is not working most likely the EGR valve is stuck or the vacuum hose that opens it is bad (leaking) so the valve wont open. check the vacuum hoses first if they are Ok then replace the EGR valve|||The EGR valve, or Exhaust Gas Recirculation valve, is a vacuum controlled valve which allows a specific amount of your exhaust back into the intake manifold. This exhaust mixes with the intake air, cools the combustion process and also prevents the formation of Nitrogen related gases. These are referred to as NOx emissions, and are a common cause for failing emissions testing.





Unfortunately, the EGR valve can get stuck, and as the test says the intake manifold can get blocked by carbon brought in by the exhaust gases. The EGR valve is easy to clean or failing that replace, and the same goes for the manifold. Any good mechanic could do that for you.|||you have a 99 with that low of mileage, wow. its bored. either the egr is plugged or the passage behind/in front of it are. you can pull it off and clean it out then clean the intake and exhaust to make sure that it is clear. you might have to replace the gaskets but if it solves the issue, it was worth it.|||A murcury Sable is a Ford, not a GM. The EGR code has nothing to do with the car not cranking. You most likely have carbon build up in the intake port. The EGR syste works like this:


Spent exhaust gases that have been burnt are on the way out the exhaust manifold. The is a passage in one of the manifolds that diverts a small amount of these gasses thru the EGR valve and back into the intake manifold to be reburned. This is to help cool combustion tempatures in the cylinders, thus preventing spark knock. The EGR valve is told when to open and close by the PCM based on a variety of perameters and data thats computed based on what the car is doing at the moment. If it is vacuum operated, its the same scenerio, except the PCM is commanding the EGR solenoid to open and supply vacuum to the valve. This adds tha possibility that there could be a vacuum leak at the hose or a pinched / damaged hose that should be checked as well as solenoid operation. In situations where the EGR valve is stuck open because of carbon deposits, this can cause hard starts, and a rough idle when the car comes to a stop. In a severe case, it can cause the car to stall. When it is not opening because of valve failure, it will not cause any acute symptoms, other than possible spark knock, which is not likely in most cases unless you are driving in a hot climate. If your car is not starting and not even stumbling or trying to start, then it cant be the cause.

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