So, a few problems... NOx, EGR, emissions

[1996BLKBauer]

So for a while now my 1996 Explorer V8 has been having a rough idle, nothing serious, I can sort of feel it in the cab, but you can visibly see the engine shaking around. It ran fine so I never worried about it. On Sunday I went to start my truck, and it blew off a Vacuum cap of the back underside of the intake, so basically it misfired? I didn't even know EFI engines could do that. So I bring it to school today to test a few things, first off the fuel pressure regulator is not leaking, and it is working just like it should. YAY! second, I hooked up a 5gas analyzer to the tail pipe to find that my NOx emissions are through the roof!!! at 2,500 rpms the NOx was at almost 400!!!!! So naturally we looked at the EGR system right away. turns out that the hose going from the EVR to the EGR was split, so I replaced the hose, and tested it again. Same test at about 2,500 rpms it went no higher the 260, but that is still very high.

We then took off the EVR solenoid, and did some tests on it. the vent is working correctly, and it works both mechanically, and electrically, so we looked at the EGR, it works just fine, we hooked up a vacuum pump up to it, and did the same test as before, the NOx was now below 100, which seems to be pretty good. So my question is, do you guys think that the valve is too clogged up to open fully or at all with the little amount of vacuum supplied from the EVR solenoid? I had to apply quite a lot of vacuum to allow the valve to open enough to bring the NOx down. Also can I simply clean the EGR valve off to fix this issue? I have this amazing foaming top engine cleaner from AC Delco that basically eats any carbon build up right up?

Thanks guys. I can pick up a can of top engine cleaner from work tomorrow before I go into school, so some input tonight would be appreciated.

 

[rb142]

Is the vacuum level good? Are there any vacuum leaks still? If the EGR has not been working for a while you could have a lot of carbon built up in there. Cleaning won't hurt.

 

[1996BLKBauer]

Is the vacuum level good? Are there any vacuum leaks still? If the EGR has not been working for a while you could have a lot of carbon built up in there. Cleaning won't hurt.

I was hunting around with some propane and a hose for 45 minutes, I saw no changes on the O2's, so I would say that there is no vacuum leaks. I will hook up a vacuum gauge tomorrow to see how the vacuum is. I did have a code for the. EGR come up about a year ago, I saw nothing wrong so I cleared it and it never came back. When it happens it seemed as if the EGR got stuck open, it almost died during idle, I gave a boot full and cleared the code and it was fine. I am wondering of the EGR got stuck closed possible. Like I said it seemed to take a lot of vacuum from the pump to bring the levels down.

 

[rb142]

Start with cleaning and see if it "un-sticks" itself.

 

[AP9]

A word of caution: last September I learned the hard way NOT to touch the EGR valve if it hasn't been touched in a long time (or ever), unless spare parts are handy. Rust had weakened the inlet tube, so I ended up kinking it and actually had to cut/tear it off, and replace it as well as the compression nut fitting on the exhaust manifold and the EGR valve itself (since the nut on the other end of the tube was frozen onto it like no other and I was not able to get it off).