austinado16

Followed Vespascuter's info from a recent EGR thread.
Using VAG-Com, in the "output tests" mode, the solenoid does sit and click. So that tells me the solenoid is alive.

Putting VAG-Com in "measuring value blocks" looking in "group 17" and then in window "4" I watched the EGR temp reading rise to over 65*C when I pulled a vacuum on the EGR valve with a hand vacuum pump. So that tells me the EGR temp sensor is alive and well.

I then hooked a vacuum gauge up to the vacuum line that goes to the EGR valve. Revving and then holding the engine at speed I got about 20"Hg initially, dropping to about 10"Hg as the engine speed leveled off. So, looks like I'm getting suction through to the EGR valve when I should.

So, I'm starting to get stumped. About the only thing I can think of is maybe I'm not getting enough suction to the EGR valve, so it's not opening wide enough for good flow, or the opening into the intake chamber (not the main passage)is still somehow partially blocked. I blew through it yesterday with compressed air and with my mouth and it sure seems pretty open.

Anyone have any thoughts?

summit25

I have cleaned the passageway from the EGR valve into the intake manifold and replaced the vacume lines to the EGR frequency Sylanoid. but was still getting a stumbling engine at idle. I understand that the EGR valve should not receave any vacuem at idle so when i simply disconected the EGR vacume line i have a perfectly ideling engine. so i thought that my egr frequency sylanoid was gone since it has been ticking loudly for several years. I assumed that the frequency sylanoid should releace the vacume to the EGR valve. Anyway my new frequency sylanoid came today ($100) and i put it in. It does not make the loud ticking so i am happy about that, but i am still having a stubling engine at idle.

It seems that the EGR frequency sylanoid should not be loudly ticking but i don't know what else to look at to find the problem.

It is great to hear about what you have been doing on your EGR system austinado16 since it helps me to learn what i can. I am just a backyard mechanic and don't have a vacuem test unit, Are they expencive and where do i find one?

austinado16

Today my game plan was dig through the Bentley book until I found all I could on the EGR system.

Finally, I stumbled across a section that talks about road testing the EGR and how the computer does it's self test of the EGR system while you're driving.

Basically, steady throttle, 43-62mph, engine at operating tempurature, and maintain that for 1-1/2-5min. While you're doing this (or should I say, while the engine is doing this), the computer activates the EGR solenoid in order to supply vacuum to the EGR Valve, thus opening the valve. The computer then starts timing how long it takes for the EGR temp sensor to register 65*C or higher. If the computer sees the right temp in the right amount of time, it does not turn on the CEL. If it does not see the right temp in the right amount of time, it activates the CEL and gives the "Insufficent Flow" code P0401.

So, I "T'd" my vacuum gauge into the braided hose right at the EGR valve, ran it out the back of the hood and taped it to the windshield. Old school diag, I know, but ya gotta do what ya gotta do. Went for a test drive at the steady speed and watched the vacuum.....basically nothing unless I was slightly accelerating. But hold it completely dead steady and poof, in about 2min the CEL came on. Pulled over, switched to the used EGR solendoid I just got, same thing happened.

From here I started working backward checking for vacuum first, right at the intake manifold fitting up in the right rear (passenger side) corner of the manifold. This is the supply source. Had a good 22"Hg at idle, not bad for an engine with 185k on it. Next, I connected to the other end of that line's dark green vacuum tube...same reading. I moved to the down-stream side of the black and blue check valve there below the MAF.....a little lower reading, but still good. Next, I checked both sides of the black device (I have know idea what it's called) that sits on the outside of the EGR solenoid and has vacuum in one side and out the other. Significant drop out the other side, which then feeds directly into the EGR solenoid and hence to the EGR Valve. By this point, the vacuum was down from 22"Hg to only about 10"Hg. I've got a spare EGR solenoid assemply, so I swapped in the black goodie from it, same reading.

I then went for a test drive with the vacuum gauge hooked to the inlet side of the EGR solenoid, and got a good 10"Hg at all times.

Finally, I went for a test drive with the vacuum gauge hooked to the outlet (EGR vavle) side of the EGR solenoid. Again, I got almost 0 vacuum unless under light acceleration.

At this point, I'm ready to condemn the EGR solenoid. $234 from the VW dealer. $104 in the aftermarket. Should be here in the morning and as always, I'll report back.

Bmthorn

and there always interesting to read!

austinado16

You can buy a standard vacuum gauge for use in diagnosing automotive problems from any parts store. It'll probably come in a blister pack with a coil of vacuum hose and some different fittings so you can T into stuff and get readings while things are still functioning, or, just run the vacuum hose straight to something and read what it is directly. They're cheap.....Sears has 'em, NAPA has 'em, Autozone, etc.

The other cool diag tool that's really a must have, is a "Mityac." This is in a nice blow molded case and comes with a hand vacuum pump that has a vacuum gauge right on it. You get a ton of fittings and adaptors and even a nice cup so you can suck oil or brakefluid out of things (like that non-drainable front differential in our cars!!). You can use the mityvac to suck a vacuum on something like the EGR valve itself, and 1)listen to the engine idle change if your passage way is clear, and the valve isn't stuck closed. 2) watch to see if the diaphram in the EGR valve has a hole in it, by watching the vacuum gauge needle bleed off vacuum...or hold a steady vacuum. 3) watch the EGR temp sensor's reading on VAG-com to know that the temp sensor is in fact working, and so is your passage into the intake.

The mityvac's are on ebay all the time. Spend up and get the one in the case.

austinado16

And them come crying back there that it still isn't fixed.

Following that, I'll post an mpeg of me cutting the car up and putting it in a dumpster.

Bmthorn

I'm not going to lie, a video of you cutting up your car would be just as entertaining if not more!

summit25

in trying to diagnose my problem i understand that there should be no vacueme going to the EGR at idle. having a vacuem to the EGR at idle causes the engine to stumble and the computer will cause a rich burn.

My EGR is never closing from a release in vacume pressure even with the brand new solenoid and all the passageways cleared.

Just my small thoughts

austinado16

That's what I've got, no vacuum at idle at the EGR valve. However, over yonder at the EGR solenoid, there is manifold vacuum passing (via the dark green plastic vacuum tube....through the blue/black oneway valve, then through the little black goodie on the side of the EGR solenoid, and then into the end (the fitting that faces forward toward the grille) of the EGR Solenoid.

This vacuum sits at the ready, for when the computer activates the solenoid. That's the time when the EGR valve finally gets vacuum.

If you are sure you have vacuum right at the EGR valve, even at idle (and not just an EGR valve that is carboned up and not fully closing) then you may want to check your vacuum hose routing. You might have something in the wrong order over yonder at the solenoid.

summit25

I know that my EGR valve is opening and closing correctly and that the passage way is cleared. and that my solenoid is brand new but i am not 100% sure with the routing of the lines at the solenoid since my computer with the Bentley is off at Best buy for service. From your previous posts i have enough to do a bit more checking tomorow so i will let you know.

Thanks