Ok, lemme sum all this up, i got a 1994 V6 3vze, I can mash the clutch in and roll to a stop when the truck gets warmed up and it will pulse and idle really bad, almost like i have a cam in the truck, and i have noticed it idles a little rough, so i got to researchin and found it could be the EGR valve sticking open so someone told me to tap on the valve and listen. i did and my truck idled up and down as i tapped on the valve toward the bottom of it, so i pulled the vaccum line off the top of the EGR and drove the truck, and my problem was fixed, but i dont wanna leave it un plugged. any ideas? is it a bad EGR valve? or could i run some seafoam in the tank and clean the flap in the EGR valve so it will close?

 

If disabling the EGR valve by removing the vac hose solved the problem, then the valve is working just fine. It is closed. Or it wouldn't have made any difference. Something is causing it to be open at the wrong time. What I haven't a clue...might try checking the VSV and the wiring for it to the ECM.

 

Ok, ill try checkin those, however when I tap on the bottom of the egr valve my truck will idle up, and down, doesn't that point toward EGR?

 

I can't really explain that. My understanding of how the valve is constructed and functions, which is thorough, doesn't provide me with any reason why that should ever occur. The valve is held closed under tension from a spring above the diaphram in the vacuum chamber above the valve. Vacuum pulling on the diaphram counteracts the tension of the spring pushing on it and opens the valve. Tapping on it should do nothing. And certainly not cause it to open/close. Not to mention being an odd way to test an EGR valve. Makes absolutely no sense to me why you would do that in the first place.

It's a long shot, but maybe the tapping sounds like knocking to the knock sensor. If so perhaps the ECM is adjusting the ignition timing to prevent it. That could potentially make the idle speed change slightly.

 

I had an intermittent idle rough problem in my 3.0 whenever I would hit a ditch or bump in the road. Tapping on the egr valve lower tube would cause it to idle funny, then go back to normal.
When I took off the egr tube to the exhaust manifold, it was clogged with carbon buildup. I cleaned it out and reinstalled. I also found a load of carbon in my upper intake plenum, so I pulled it and took it to have it boiled at the radiator shop. I have put 6k miles on it since, and no more issues.

 

Well someone on here had told me about tapping on the EGR so I tried it and that's what came to happen to me, however I bought a new EGR valve today and hopefully will be able to install tomorrow, and if I come to fine a lot of carbon build up I may just take a trip to get some seafoam I hope this works, its a $150 gamble

 

The vaccumm routing on the truck is fine, their where their suppose to be and theirs not a broke or split line anywhere that we can see, it about has to be a clogger EGR right?

 

now if my EGR valve is the cause for all of this unconsistent idle and caming sound, would it throw a code my way, or not necessarily?

 

put on the new EGR and the truck still does it, what a waste what else could it be fellers?

 

if its not opening the egr temp sensor should throw a code 71

 

When you replaced the egr, did you pull the curved pipe it connects to out of the upper intake plenum and inspect for carbon buildup? I am referring to the small curved pipe connected to the egr that runs into the upper intake plenum, connected by two bolts. It has a pipe that extends into the plenum, and mine was clogged with carbon. There was also a load of carbon in the plenum that I had to have boiled to remove.

 

It goes away when you unplug the vacuum line to the EGR; right? If so, the problem is in the vacuum or VSV...NOT the EGR.