EGR valve question

What's an EGR valve and how would a "bad" one effect my Crown Vic's performance? I've been told they are notorious for going "bad" on this
particular vehicle ('89 5.0) Thanks! Great group for helping each other out! Bob/Orlando
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EGR stands for Exhaust gas relief valve... its all the emissions crap.
I dont know exactly what it does... but a bad one will cause a car to run crappy.. my fathers 1991 E250 van had one go bad and it ran horrible until he got it replaced.
Well best of luck. Ken

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The EGR is an acronym for Exhaust Gas Recirculation. Exhaust gases are introduced into the combustion chamber to reduce the combustion temperatures lowering the NOX emission. For the model engine you have they go bad in two ways. Stuck open and closed. When in the open position it will cause rough idle, stalls and low power. It can also drop fuel mileage. When stuck closed will cause ping under heavy load, no other drivability symptom may appear. Depending on how it fails, it may not cause a code.

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.................. in simple laymans terms a percentage of the fumes flowing through the exhaust are "recirculated" back into the engine to be burnt again, this helps the ozone layer by reducing the HC's and CO levels your engine produces. this is done via the "EGR" valve located between the exhaust system and the inlet manifold. not quite sure about "lowering the combustion temperature". Introducing hot exhaust gas back into the engine will increase temperature, however indeed if faulty it may be either stuck in the open position which will cause a few idling problems, or may be stuck closed in which case you may not notice any problems at all.
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EGR is not for HC's and CO's, It's for NOX.

You also change the mass of the air/fuel mixture. This changes the peak temperature the combustion process can achieve. There is quite a lot of science behind the reason for EGR. I would suggest before you post again, you have a better understanding of what you are talking about.
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Is there an easy way to test if an EGR is fuctionning properly?
Thanks
Matt
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If you don't get any codes, the EGR is probably OK. Perform KOER ('Key On Engine Running' diagnostic test) if you want a positive confirmation.
wrote:

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Yes re-introducing exaust into the engine lowers the cumbustion temp, thats what lowers NOX.
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I replaced a few on my '84 T-Bird with the 5.0L. They would carbon up and, after a while, any little grain of crud flying by would stick, causing the valve not to close properly. Highway was fine, for example, but when I'd exit and stop at the light, the thing would chug and churn, usually dying.
Sometimes it would clear itself but I got good at revving the engine while using an extra hose to pull vacuum and open the valve so the crud would go on thru...
PoD

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