I recently replaced the rear vcg (valve cover gasket) on my car, and in order to do that, the IM (intake manifold) had to be removed. At the same time, I decided to clean the egr passage in the intake manifold. I've never read of anyone on mx6.com doing it, but I found some writeups and threads on a 626 forum, so I thought I would share. I'm sure some members have done this, but it hasn't been mentioned much.
Once the IM was off, I sprayed tb (throttle body) cleaner in all the intake runners, and did the same for the egr passage. I kept spraying in each runner and tipped the IM so that it ran out of the tb. I stopped when the liquid coming out was pretty clear. I then put the IM back on the car and after a few days started getting the code P0400, EGR Passage blocked. This code got me searching the internet, and I found the 626 forums where this has been mentioned extensively, and they talk about cleaning out the egr passage on the tb side. I had not removed the tb when changing the IM gasket, so I decided to follow the writeup here: scortes's 1996 Mazda 626 on CarDomain - Page 3
This guy calls the egr passage the pcv passage, and calls the idle air passage the egr passage, but other than that, it's a decent writeup. I broke the coolant connector because I pried on it too much, luckily a new one was less than $10 at the dealer (iirc). If you look at what he calls the pcv passage (actually the egr passage), that's what mine looked like before...here's what mine looked like after:
Because the IM had already been put back on the car, I did it like this guy in the writeup, but instead of spraying anything into the egr passage on this side, I recommend scraping all the buildup out, because otherwise, the excess liquid goes all the way down the passage and into the egr, and then a few days later you get another code for the egr not working (trust me)...and getting the egr off is a b!tch, so trust me when I say that scraping the carbon buildup out is the better option. The spray doesn't penetrate through the buildup anyways. I posted these pics in another thread too (http://www.mx6.com/forums/2g-mx6-general/215834-new-here-please-help-2.html#post2095402
), but I thought I would start a new thread to bring more attention to this problem.