I brought this up in another thread, but since my problem seems a bit different I thought I'd start another one.

I've got an 0302 code and I've run through the checklist of things which might be causing it. Here's where I'm at:
-EGRC solenoid valve, removed, tested and working properly
-pipe from EGR to intake, did not remove it or clean it but when I push up on the EGR valve diaphragm while the engine is idling, it will nearly stall. So it looks like the passageway is clear enough to work.
-EGR Valve, does NOT lift when the engine is revved. So today I jumped a hose straight from the vacuum source and was able to get the valve to lift all the way up. So, judging by that, the EGR valve looks ok.
-All hoses in the system have been checked and are clear

So the main problem is that I'm not getting any vacuum to the EGR valve. which means it is basically stuck closed and I'm getting the 0302 (low EGR flow) code. makes sense.

Since the only other piece in the system is the BPT valve or something related to it, I'm thinking that must be it.

Has anyone had a BPT valve go bad? Is there a good way to test it? I might just replace it but is there a chance that the valve is okay and I'm losing back pressure somehow? Does the main exhaust return pipe (from manifold to the EGR valve) ever get clogged with carbon? I'm almost positive I don't have an exhaust leak. If anyone else has seen the same thing, let me know. Thanks.

btw, BPT valves are only 60 bucks so I might just take a chance and replace it.

 

That "test" you did will tell you nothing about the flow through the EGR tube from the valve to the intake manifold.

The pipe is definitely clogged. Completely. Seen too many of them.

Take it off and clean it out.

 

i have no idea where people got this "push the valve" or "watch it move at WOT" from. 0302 is caused by the sensor on the small pipe which is probably completely surrounded.

http://forums.maxima.org/showthread.php?t=501941

 

I got most of my info from the FSM. It clearly states that with the engine warmed up and under no load that you should feel the EGR valve lift when you rev up to 3000 rpms. I feel absolutely no lifting. If I apply a vacuum directly to the valve bypassing the solenoid and the BPT then it lifts easily. So I'm definitely losing vacuum because of a BPT valve or possibly a clog in the tube that connects the EGR valve to the BPT valve which would prevent me from getting back pressure to the BPT.

 

I can't argue that there is probably plenty of carbon in that tube and I am going to clean it out anyway. But..... this is how I understand it:
Pushing up on the EGR valve will route the exhaust gas back to the intake manifold through that EGR tube. Putting exhaust gas back into the intake changes the mix of oxygen and inert gas going to the engine and when you do this at idle, the engine runs roughly or possibly stalls. check out the EGR entry in wikipedia:

http://en.wikipedia.org/wiki/Egr

Soooo... let's say that the EGR to intake tube is packed solid. If I push up on the valve none of the exhaust gas will make it to the intake so nothing should happen.

Is there a flaw in that logic?

 

You push on egr to open,,engine stutters or stalls, the passage is open to intake....none or slight change in engine performance equals clogged tube.

 

Thing about auto repair is that one must be open to different scenarios. From my POV, if the "test" on the EGR worked, then there is a clog somewhere. Some have replaced the BPT and that has fixed it as well. I don't know how much you've done, but in addition to the EGR pipe from the IM, there is a much smaller (thinner) pipe that goes from what I guess is the BPT TO the EGR. The ONLY thing that connects that pipe to the BPT is a piece of rubber hose. If that hose is OLD, that can also cause a blockage.
http://target.pg.photos.yahoo.com/ph...e2.jpg&.src=ph
To my old fashioned way of thinking-if 90% of people have had the same issue and the same method fixed it, chances are that's what's wrong....Besides, look at the cleaning as preventive maintenance. You get to see how it all looks and you'll feel real good after you clean it, put it back together and it runs better.

 

Right, I'm trying not be stubborn about this. I just hate doing a repair by guessing what's causing the problem... I like to have a pretty good idea what I'm going after before I start. I realize that auto repair doesn't always work that way.
Anyway, I was suspecting that pipe that connects the BPT valve to the EGR since a clog there would prevent the BPT valve from seeing any back pressure. How is that pipe connected to the EGR? is it threaded in? or is there a nut or a screw?

 

right, mine nearly stalls when I push it. If I held it up, it probably would stall.

 

A nut tightens it-almost like a banjo bolt: and the hose I mentioned at the BPT end.
http://target.pg.photos.yahoo.com/ph...e2.jpg&.src=ph

http://target.pg.photos.yahoo.com/ph...e2.jpg&.src=ph

This one'a little blurry but it'll give you an idea:
http://target.pg.photos.yahoo.com/ph...e2.jpg&.src=ph

 

nice, thanks. I'll see if I can get it off tomorrow.

 

Sounbwoy, I was trying to view your pics via the links in your message. Get a message that you have no shared pics. Am I doing something wrong?

 

Hmm. In Yahoo's never ending quest of "improvement" it appears that I have to go back and setup my stuff again. Give me about 30 minutes then try again.
EDIT: For some reason they flagged my account as "Age Restricted"??? I've sent them an email, but I don't know how long it will take for them to make a decision. Send me an email address and I can email them to you over the weekend if you need them....

 

Sounbwoy, do you happen to remember the size of that nut on the small EGR valve to BPT pipe? I'm going to have some time to go after it tomorrow and I don't have a full set of metric wrenches yet... I know I know.

 

I wanna say it's a 10mm-no bigger than 12mm..

On another OT question....I think I'm going to move my pics somewhere else...Anyone have any recommendations? Just someplace to archive and store....You can just email or PM me to avoid cluttering up the thread...

 

This site is fantastic. I found a solution to my engine code problem. The description of the problem and the solution were right on the money. I only removed the small tube between the EGR and the IM. I did have to cut the end off the bolt closest to the large tube, but after removing 4 bolts, the small tube came off. Wasn't as hard as I thought it would be. I had to drill the carbon crust at the IM end of the small tube. It was hard. Do have one question. How long, or how many miles, before I have to do this again?

 

about 15K miles until it clogs again if you cleaned EVERYTHING out. make sure u remembered to clean out the part from the Intake to the pipe as well since that gets clogged up even worse (took me 2wice as long to clean that out)

Ouch you cut the bolts when a 6MM lug would have gotten them out for you oh well...

oh and if you get an 0302, look no further than the small EGR tube being clogged because that is where the sensor for that corresponding code is anyways, if you get there and it's not clogged then look at the valve (which only rises in pre 97 models, after that the "watch it rise" test doesn't work)

I find it weird that alot of people are getting this code around the same time I got it, anyways if anyone needs info on how to remove the pipe I got an excellent guide 2_da_MizzaX wrote, PM me with your email and I'll fwd it to you.