EGR reroute?

[MoonieGT]

Has anyone done this? http://www.miata.net/garage/egr0902.html

What does the reroute do to make the EGR happy? Does it trick it into thinking that the car is always under enough throttle to stay closed?

[jakepkoe]

A friend just bought a '99 with the 'check engine' lit. It pulled an EGR code. He tried this and it worked. We couldn't figure out what difference it would make but tried it anyway. After reading the internet, he determined that the lower vacuum port gets clogged causing the EGR to be non-functional. I guess the upper port stays fairly clean and provides consistent vacuum.

[Keifersmith]

My 99 just recently started throwing the P0402 again. It did it about 12-18 months ago and I cleaned out passageway in the upper intake manifold. Not too difficult but a pain if you have to continually reclean it. Think I may give this a try and see what happens. Doesn't sound like it's "tricking" anything, just bypassing around the problematic passage in the manifold.

[jakepkoe]

Spoke too soon. We did this on Mike's car and disconnected the battery to reset the computer. All was good. This weekend, 20 miles or so after the autox, the CEL came back on. I guess he's in for a thorough cleaning of the intake manifold.

[MoonieGT]

I just stopped by Autozone on the way to work and gave it a try. I may be imagining things but I think the car is idling better than it was before.

I've also cleaned the upper intake manifold and the EGR valve. I couldn't believe how dirty the intake manifold was. Half of it was covered in black powder and the other half was oily goo. I thought that I had it fixed after I did that, but 400 miles later the light came back on. Now that I've done the cleaning and the reroute hopefully I'll be good to go...