Testing EGR function on M104 motor - not much change in idle speed RPM with valve open/closed

[bondavi]

I have a 95 C36 that failed smog due to the EGR valve. Passed other tests with flying colors otherwise.

I removed the EGR valve and cleaned it, verified it was holding vacuum, and closing/opening the valve.

When I have the car running, sucking on the vacuum line does change the RPM's a teeny bit but not much.

I thought the car would almost stall if I did this, but it does not.

I cleaned the EGR pipe going to the throttle body as well, verified it was clear. Also verified the exit of exhaust gases from the manifold side.

EGR valve holds vacuum, shuts and opens.

But does not seem to have much effect on the engine.

What is the proper behaviour of closing/opening the EGR when the engine is idling, warm?

Thanks in advance!

[Sulaco]

The EGR pipe that runs around the back of the engine is definitely going to be completely clogged with carbon buildup. It's a common M104 problem. Disconnect both ends of the pipe, but leave it attached to the car. Attach a speedo cable to a drill and run it through the pipe turning as fast as you can get it to turn without bunching up your cable. This will clean out the pipe without removing it from the car (which is a massive pain to do, since its bolted to the back of the engine on a bracket).

9 times out of 10, an EGR code on an M104 car won't be the EGR valve, just the pipe I mentioned.