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I followed the tip on Mike's webpage to check for any problem with my 6 since i am getting sub mpg, and this popped up. Engine code 16, EGR - Exhaust Gas Recirculation. I have no idea what that is even after reading the description on Mike's page. Help, what does this mean? I know it is not good and probably eating into my hp and millage.
 

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I'm not looking at my page now so I'll try a fresh description:

EGR - Exhaust Gas Recirculation - as the name implies, is an emissions control system on the engine that is designed to feed a bit of exhaust gas from the exhaust manifold back into the intake manifold. Exhaust gas is generally inert (that is, it doesn't burn or contribute anything to the combustion process) and in fact actually cools the combustion peak temperature down. This help to stem the formation of oxides of nitrogen (commonly known as NOx) which require high temperatures to form. By cooling the combustion down a bit, you reduce the formation of these smog-forming gases.

But you don't want EGR all the time. For example, at idle or at WOT (wide open throttle). Even at part throttle cruise on the highway, you want on;y measured amounts of EGR. The PCM - computer - is responsible for looking at the load the engine is under, it's RPM, temperature etc and determining how much EGR to add. It modulates the amount of exhaust gas recirculated by manipulating two vacuum solenoid valves, one called the "EGR vent" and a second called the "EGR vacuum". Collectively, these two solenoids control the amount of vacuum applied to the EGR valve itself. The EGR valve is what actually allows exhaust gas into the intake manifold: more vacuum equals bigger opening.

The EGR valve has a sensor on it that the PCM can read. It tells the PCM how far the valve is open. As I said earlier, the PCM controls how far the valve opens to modulate the amount of gasses recirculated. It uses this sensor to see if the valve is where the PCM thinks it should be. If it's not, then there's something wrong in the EGR system and the PCM will put up a code 16.

It's a vacuum-operated system so the best place to start looking for a problem is in the vacuum lines at the back of the intake. Below the back of the intake is a metal bracket with two solenoids on it. (It's deeply buried and tough to get to.) These are the EGR vent and vacuum solenoids. Check the vacuum lines going to these. The EGR valve itself is under the throttle body (also tough to get at). Check the vacuum lines to it. If all the vacuum lines check out (condition as well as routing), you'll need to get the vent and vacuum solenoids out and test them for function. The PCM checks the windings in the solenoid but can't check if the solenoid valve is actually functioning; you'll have to do that. The EGR valve may be stuck or seized. It could be that the system is functioning properly but that the sensor on the EGR valve is bad, telling the PCM lies :D

Good luck, HTH
 

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Discussion Starter #3
Man that's deep, i'm probably gonna need a few days to dissect all that. Thanks for the help.
 
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