by Steve Chaffee - 13 January, 2008
I'd like to offer this information to owners of '99-'00 Miatas that after many miles develop a rough running engine and a recurring check engine light for excessive EGR flow, the code is 0902 (This may work for other years, but I know it works on these two years!). The conventional fix is cleaning the EGR vacuum passageways to remove “carbon”. Unfortunately, this is a lot of work and may turn out to only be a temporary measure at best. I saw this on the web and the mechanic said he fixed 12 for 12 miatas. I tried it on our '99 and my daughter's '00. Result: no more check engine lights and a much smoother running engine. So if you really don't want to get too dirty cleaning stuff try this alternate!
PERMANENT FIX: Remove the vacuum hose (about 1' long) going from the EGR Booster on the fender wall to the vacuum port on the side of the intake manifold (Ref: schematic on hood). Install a new hose that goes from the EGR Booster to the vacuum port (unused) on the top front of the intake manifold. Cap the port on the side of the intake manifold with the cap from the formerly unused port. That's all there is to it!! Couldn't believe it was so simple there are even unused clips next to the throttle assembly you can use to hold the new hose in place.