FYI: Code 51 on 95 Metro

[seb001]

I got this code 51 about two years ago and decided to look into it this weekend. A few threads talked about the EGR and the MAP sensor.

I removed the EGR. The ports were not blocked but the valve was full of black soot. Cleaned it with brake cleaner (That stuff just removes everything). Also used a few Q-tips to removes large deposits. Sprayed WD40 in the valve. By the end the valve stem could easily move up and down. Put it back into place.

As I was replacing the air filter, I noticed that the duct leading to the cover was partially obstructed. There is a gasket (1" wide rubber) between the filter cover and the section leading to it (on the left). This gasket was inside the duct, blocking about half the air flow. I think that someone (mechanics or me) remove the air filter and did not reassemble properly. I'm thinking that it was only a problem on the highway and the pressure in the intake was too low because of the restriction. (Hence the reference to the MAP sensor)

In any case, the code is gone. I went on the highway, but could not feel any difference.