The EGR valve was clogged with carbon deposits.
Had I known back then about the below-mentioned procedure, I would have done that and replaced or cleaned the EGR valve myself.

 

I almost bought a used one for $75 until I realised when I looked at the valve at the junkyard counter it would be hard for this to be broke.

 

The car did idle a bit better with the new EGR valve, but not for long. In the end, I ended up cleaning the ICV and MAF, and that seemed to make a much bigger difference. I really can't tell in how far the EGR valve was the culprit...

 

hell yeah run better and more performance, thats killing two birds with one stone brotha,

 

iam getting ready to do a bunch of Maintenance as well as a custom intake and heatsheild, just waiting on the maf adapter to be made. so all this info helps very much.

 

anyone have a picture of the stock plastic plenum tubing that goes to the throttle body showing the vacuum hoses? I'll tell you what to pull out

 

<center><img src="http://pictureposter.audiworld.com/47456/3inhose4.jpg"></center><p>

 

Ok, see that yellow vacuum solenoid switch sitting loosely above the intake change over diaphragm which is on top of the cruise control motor?

Hmmm, let's start again. That yellow vacuum control diagram is the EGR control solenoid. As you can see it has 5 connections.

Connection #1 is the hose that goes over the intake switchover valve and then disappears below as it connects to the EGR diaphragm. This is how you test if the EGR is working. You disconnect this hose and with a mighty vacuum pump, let the engine idle, apply vacuum in there and see if the car dies or idles very rough. If no response, your EGR ports are clogged up or if the mighty vac cannot apply vacuum - then the diaphragm is ripped.
Again, like I said, your EGR needs to be working so that no CEL will happen.

Ok let's move over to connection #2. It has a U shape hose that goes to connection #3. That was easy Anyway, that port of connection #2 is the switched port by the solenoid. This is how the ECU will determine "test mode" or "normal mod" - I mean mode

Connection #4 - is behind the yellow solenoid and it seems to disappears underneath that light blue and black one way valve (there's too much blue and black in this pic hehe). That hoes 'T's with the vacuum reservoir located in front of the engine next to the coil pack (1.8T's don't have 'coil packs' - just 'coils', we do . Why does a EGR need a constant vacuum source? It doesn't during normal mod. It's only for testing - aha!

So what is connection #5? eh ah dum dee doo - [unplug, seal] :^ That goes to - on a stock tubing, post throttle body port. The stock tubing leading to the MAF senses vacuum when you accelerate. This is amplified by that solenoid switch (it's not just a vacuum switch) using the stored vacuum. This in turn will create enough vacuum during acceleration to open the EGR valve.

Why does the light not go on? Because the trick is when Motronic will 'test' the EGR. During idle or random cruising speeds, it will cycle the solenoid and connect stored vacuum to the EGR. It will measure a drop in rpm and increased EGR temps (via the sensor) and if there is change, the ECU is happy. Then it will switch back to normal mod. Removing the port to the intake track will eliminate the EGR from opening during acceleration, so instead of getting a mix of 10% warm inert exhaust gas in the intake stream, you fill it in with 100% 14.7 :1 of pure air/fuel mixture.

Hope that helps - free power is king :P

 

ok i will have to test the valve if it is bad can i just clean it and and then proceed to do this?

 

If EGR valve is working, yes.