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· Registered
13 Posts
Discussion Starter · #1 ·
Hey there my engine was running v poorly and I was getting a code 34 (map sensor low voltage ie high vacuum ie not enough air coming in.) I checked my egr valve as demonstrated in a Chris fix YouTube video and it failed the test (didn't hold a vacuum) so I replaced it. Makes sense, the vacuum line couldn't open it so air/exhaust couldnt get in. Easy breezy, fixed my problem, code went away.

Just wanting to learn more about the egr system though. So it redirects exhaust gas back into the intake right? But looking at it on the iron duke its not connected to the exhaust, it seems to just open a passage in the intake manifold. What gives?

There's another valve on top of the air box that connects to the exhaust and by the looks of it does what the egr valve is described to do. So what the ****? What is this little nugget called? Also looking at the bottom of it there are two vacuum ports. One goes up to a sensor in the air box (while I'm asking-whats that piece called?) But the other is disconnected. Should that have a line that goes somewhere? Nothing is an obvious candidate. Egr solenoid has all the ports occupied.


· Mr Goodwrench's Evil Twin
587 Posts
Iirc in an iron duke the piping for the EGR is integrated into the intake manifold, at least in part. The EGR valve itself should have a vacuum connection on the top and on the bottom, where it sits on the intake, there should be 2 ports. 1 is for the incoming exhaust gas and the other is where that gas is fed into the intake air stream.

By the sounds of it (pictures would help), the other thing you describe is called a thermostatic air cleaner AKA heat pipe AKA heat stove. It's sole purpose in life is to aide the engine in getting up to operating temperature quicker by taking radiant heat from AROUND the exhaust manifold (it does not collect any exhaust gases) and places that heat into the intake air stream. That's the theory, at least. They are pretty much worthless at doing what they are supposed to and it hurts nothing to just remove it. The attached image is just one I found on google, may or may not be representative of the iron duke exactly, but it gives a general breakdown of the individual components of the thermostatic air cleaner


· Boozebag
10,859 Posts
EGR is supposed to (believe it or not) cool the incoming air mixture and reduce oxides of nitrogen (ha)
Works great when new, but over time, it degrades to being almost useless.
Unfortunately, the ECM doesn't know this is happening.
You can disconnect the EGR, but it will trigger the CEL in your dash
There is not much improvement in performance (to eliminate it) unless it is not functioning correctly
I have eliminated many, but there is not much advantage other than it looks better
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