I had trouble with a random miss all through 2005 and into 2006 and I think I finally solved the problem. The car finally threw a code for bad EGR valve. This was replaced once under warranty in 2000 and has about 35K on it before it failed a second time. The thing was carboned up and didn't close completely. The new EGR solved the miss problem. Apparently the slight leak was causing the rough idle-esp. with the AC on. I tried cleaning it first and just couldn't get down in there enough to get it to seal. I'm going to try and soak it in carb cleaner gak to see if I can get it clean enough to serve as a spare. While the new EGR was on order I blocked off the valve and the bad idle went away, of course, it continued to show a code because the MAP sensor did not sense it opening.

 

Any idea why the EGR carboned up?

Is it normal?

Could it be caused by a missfire, such as a bad plug wire or opti?

I replaced an EGR once for the same reason and now the new
valve is getting a lot of carbon @ 20k miles.

 

Probably the way I drive. The first one went out in a little less than 40K. I changed the plugs and wires chasing the miss but never cured it. It was always worse with the ac on and would shake the car bad enough to set a "random miss" code. The compressor went out and after replacing it most of the problem went away so I figured that was it. That's when this thing with the EGR came up. Oddly, now it has a stumble on low speed takeoff but no miss under full throttle. I have no idea what is causing that. I'm going to clean the ICS motor and the throttle plate and check the tps for linearity and see if anything inproves. Usually if a car will perform at full throttle, it doesn't have any other miss problems.

 

This is exactly why I deleted the EGR function when I installed headers. I bought a block of kit that consists of 3 plates. Install is very easy and the EGR was tuned out by Ion. I had been through at least 3 EGR valves. No no more worries.