Just failed my Massachusetts emission NOx (at cruise) - 6.00 with a 3.00 limit. Two years ago same test was at 0.97 or something. From what I've gathered from searching this site it is probably either O2 sensor or blocked EGR ports.

The EGR valve is lifting OK and I'm not throwing any codes. When I apply manual vacuum to the EGR valve at idle the engine does run a bit rougher but not terrible. Just a little trembling. I expected it to almost stall but that wasn't the case.

Does just a small change in idle with EGR open idicate blocked EGR ports or is that fairly normal?

If it is blocked ports, I've read in this site that they can be cleaned after drilling out the dimples in the intake manifold. Does anyone have more info or know where I can find info about how to do this? Is this smoething that is done with the manifold still installed in the vehicle or do you have to remove it? If it is done in the vehicle how do you prevent the drilling chips from falling into the manifold (to get sucked into the engne when it starts)? With the manifold removed can the ports be clean good enought without drilling? Is ther just one dinple to be drilled out for each cylinder?

Anyone who has done this please share your experience.

 

Bump!

Anyone please.

 

Bump...looking for answer too

 

You dont need to clean the ports with a drill
a dentist type pick works pretty good

Its most likely a problem with your egr because nox is reduced by reducing the heat in the combustion chamber which is done with egr