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Old 25-01-2006, 11:50 AM   #1
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EGR Valve

What exactly is the function of the EGR valve?

Many I have spoken to suggest blanking it off, but what consequence would this have?
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Old 25-01-2006, 07:33 PM   #2
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You will help to pollute the air:

EGR Theory. EGR serves one purpose and one purpose only. That purpose is to reduce Oxides of Nitrogen (NOx). Undernormal combustion, Nitrogen(N2)Oxygen (O2) in the air and Hydrocarbons (HC) in the fuel combind into water(H2O) Carbon dioxide (CO2) and the Nitrogen remains unchanged. Under very hot combustion temperatures, the Nitrogen reacts with the other two byproducts and forms Nitrogen oxide (NO). After being released into the atmosphere, it picks up another Oxygen and becomes Nitrogen dioxide (NO2). In the presence of sunlight,
it combines with other compounds like Hydrocarbons and forms Smog. Since exhaust gas is inert (very stable) it doesn’t burn again. So by being introduced into
the combustion chamber, it will lower combustion chamber temps enough so that
the Nitrogen doesn’t react with the other compounds and is passed unchanged out
the tailpipe thus not contributing to smog.

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Old 25-01-2006, 09:03 PM   #3
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However as the conditions required for the production of Nox only really exist when the engine is running VERY lean, this only occurs at idle condition.

As Bazzle has said the exhaust gas reduces the oxygen content in the "air" so reduces the condition. The problem is that this then reduces the engine output and creates smoke, so burns more fuel and creates more polution that way. This is why diesel cars tend to emit a puff of black smoke when pulling away from rest.
In addition the recirculated gas polutes the oil and intake tract.

If your car has a MAF sensor then you can't block the EGR as that would be detected by the MAF, otherwise you can block the vacuum tube as a test.
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Old 25-01-2006, 10:14 PM   #4
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Not really sure what it does but....

I had a Vauxhall Vivaro 1.9dti van a couple of years ago which broke down 2 months after new. I called the AA out.

He knew exactly what was wrong as quite a few of these had broken down. What he did was to take out the egr valve turn it around 180 degrees and put it back.

He did say that it was either permanently open or permanently closed cant remember which but that I would get much better performance and there would be more smoke.
I had it like this for a week until the dealer fixed it, but wow!! what a difference, and it made a nice growl when flooring the throttle. That week was the best time I had with that van.

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Old 25-01-2006, 11:21 PM   #5
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Mine was replaced at 36k under warranty, engine light came on and did not go off, MB replaced and has never come on since (done 70k now!)
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Old 26-01-2006, 08:11 AM   #6
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Note moved to the other EGR posting

Last edited by tamrsoft; 26-01-2006 at 08:19 AM.
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Old 26-01-2006, 05:56 PM   #7
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This thread might be of interest to you:

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Old 27-01-2006, 03:55 PM   #8
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I have had on a couple of occasions when accelerating heavily the response from the engine as described in the above link. Have now disconnected the EGR and replicated the style of driving and had none of the ill effects. Lets hope it continues!!
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egr, valve

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