I have a code 71 (epic threads all over the place detailing my problem.) I've cleaned the EGR valve and the connecting sensor valve. I've cleaned the sensor. I've tested the EGR valve by sucking on the vacuum hose with the engine idling and it almost stalled, so this means the EGR valve is functioning properly. However, I still think there is some blockage somewhere and I don't think it's in the head. I had the head off about 5000 miles ago for a valve job during a head gasket replacement and I had the thing jet tanked and cleaned pretty throughly.

I was searching youtube to see what other techniques there are for cleaning the EGR system, and came across this:

http://www.youtube.com/watch?v=3LjhH...eature=related

I know it's for a diesel, but couldn't the same technique apply towards a regular petrol engine? Couldn't you attach something to the fuel rail that feeds a caustic chemical into the engine that will burn off and dislodge some of the carbon?

 

That valve would be the vacuum switching valve.

http://www.autoshop101.com/forms/h61.pdf

 

Yes, the "EGR modulator" ? I've already tested that as well and also swapped it for another of the same model/part number and it still acts the same. I know that's functioning properly.

But what about the EGR cleaning? Can the ports inside the head and throttle body be cleaned without a teardown?

 

Remember that it won't run when you disconnect the air duct (because it needs the MAF signal) so you'd have to think of some other way to inject. And be VERY careful to not let "too much" in; I heard of a case where someone was "cleaning" their intake with water, and accidentally let it suck in a cup full. It hydro-locked (momentarily) and bent the connecting rod!

When you had the head tanked, did you do the plenum (upper intake manifold) as well? The EGR enters the plenum through a ~12" tube down the middle of the plenum. When I removed mine, it had so much "gunk" I almost couldn't get the tube out. If yours is as bad as mine was, the whole EGR system may be working, but no exhaust gas enters the plenum. Cleaning it is a messy job (I used a bottle brush and paint thinner) because of access, but it's only work. And removing the plenum is nothing compared to a head or timing belt job, for instance.

 

I did not have them do the upper intake, but I did have that off while the head was being cleaned and in my downtime I scrubbed the heck out of it. So the EGR port on the back is clean. I also bought a gun barrel brush a fre months ago and cleaned it again the same time I cleaned the EGR valve itself. I also cleaned what I could of the head (while oven cleaner soaked inside of the EGR) and I was able to clean a bit with a wire clothes hangar. I was able to jab the hangar in a bit, but where it bends is where I was unable to go any further.

So, in theory, I should be able to setup some sort of injection system with a nozel on the intake hose and filter in some seafoam or other cleaning agent, and that should burn up and help clean out the EGR system? I was thinking of drilling a hole on the intake tube and putting some sort of nozel in so I can add cleaners (carb cleaner, seafoam, etc...) to clean the throttle body. Would this work?

 

I really don't know if an injection method would work. I know it sounds easy and quick, but you can never really see what's going on.

When I cleaned my plenum (upper intake), I did most of it through the throttle body opening. That's about 2" in diameter, vs. the 3/4" diameter that the egr tube comes through. Did you look at the plenum through the throttle body (left) side? Mine had enough gunk "coating" the sides that a gun-barrel brush from the right side would have left a good 1/2" all around.

You still have the problem that you can't turn all the corners (it has what look like freeze plugs which you could remove to do a real cleaning, but I wouldn't even think of that unless I was sure I had the correct replacement plugs in hand!)

Do your idle-ups (power steering and AC) both work correctly? If they do, that suggests you don't have TOO much dirt. On mine, the dirt was so pervasive that those vacuum ports had been clogged inside the plenum!