I have a 2002 Mazda Protege LX with about 165,000 miles on it. In the last month I had the EGR valve replaced and after that my car started acting goofy.

Upon deceleration, when my cars RPM meter hits 1.5x, it will flutter back and forth between 1x and 1.5x. The faster I am going, the more times it will go back and forth before settling into the idle. The Engine light is not on.

I took it back to the local shop and they suggested that the EGR valve they installed was either faulty or inappropriate and installed a Mazda (rather than aftermarket) valve. The problem is still there though, and they essentially said "We don't know what the problem is."

After searching the internet I found a post with three other Mazda owners who had the same problem but there were no updates. One suggested reflashing the ECU.

Any ideas what the problem is and how to fix it?

 

I disconnected the battery and drained any left over charge by turning over the engine once. Left it unplugged for an hour and reconnected it. The ECU reset itself and apparently fixed the problem.