| This is actually Delbert's last photo, with everything back
together again, so the EGR valve you see at far left is brand-new.
I figured this was as good a place as any to start.
I'll show and describe to you the photos Delbert took, just so you have some sort of visual background on this, then I'll let Delbert take over with his narrative.
The fuel rail is the shiny aluminum bar at the back. The four injectors are immediately in front of that.
These photos are taken from the vantage point of you standing at the car's front bumper and looking down at the engine.
|These are the engine-end parts of the Civic's fuel delivery
system. The unlabeled black thing to the left is the purge switching
valve for the fuel evaporative emissions system. Honda used a fuel rail
as a mounting point for the valve; the valve does not interact with the
|This is the EGR valve itself. It's just a variable
gateway: It lets some exhaust gas into the intake, or a lot, or none at
It all depends on the signals received from that electrical connector
at far left. Engine intake vacuum is expected to do the actual work of
pulling exhaust gas into each cylinder.
The EGR valve sits on top of the thing labeled "EGR valve inlet" in the next photo.
|As we peek behind the valve cover at the top of the intake
see that the fuel rail, injectors, EGR valve and EGR
Chamber Plate have all been removed. This exposes the sheet metal
gasket that's sandwiched between the EGR Chamber plate above, and the
EGR portion of the intake manifold below. Small holes are let into the
gasket. These holes communicate with the Chamber Plate to distribute
EGR gases to each cylinder.
Delbert has stuffed crumpled paper towels into the injector holes in the intake manifold. This to keep dirt out when the holes are open..
The large hole to the far left of the gasket is the EGR outlet hole into the Chamber Plate. It allows gas to flow from the EGR valve into the Chamber Plate atop that gasket. The smaller holes in the edge of the gasket closest to you are the feeds for each cylinder from the Chamber Plate.
And that's a new gasket you see. The old one was thoroughly black with carbon.
|We remove that gasket, the intake manifold ports themselves
are now visible. These ports also plug up with carbon and must be
delicately cleaned with a drill bit (see Delbert's
text further down
|This is the EGR Chamber Plate, shown here upside down. It
sits on top of the metal gasket in the previous photo. This serves as a
"distributor" for exhaust gas: It makes the output of a single EGR
valve available to all the cylinders.
Gas flow is from the EGR valve outlet at far right (on the left when installed) to the large open space in the middle, then through each of the convoluted runners ("Chambers") to each cylinder's port in the intake manifold. The small numbers you see are each cylinder's, from timing belt end to distributor end.
|Above I showed you a clean Chamber Plate. At the top in this
photo is the Chamber Plate before it was cleaned. Every single
part of the EGR system is subject to carbon buildup, and it all must be
cleaned off to ensure proper gas flow.
An exception to this rule is the port which communicates exhaust gas from the exhaust side of the head to the EGR valve on the intake side. It is of sufficiently large diameter that it's unlikely this will ever become occluded; the problems start at the EGR valve itself.