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« on: February 12, 2011, 08:22:23 pm »
I don't see how its an issue. As Charlie said, EGR only works when the car's decelerating. If you've got a manual Fiero, then its supposed to have DFCO. That means if its in gear above 1800RPM, with no throttle input (full vacuum) its supposed to stop firing the injectors and just let the engine turn with the transmission/wheels. At 1800RPM the idle picks back up and it starts firing the injectors again. You can feel it if you engine-brake in a manual Fiero, it'll buck slightly at 1800RPM, that's DFCO turning off and the the idle picking back up. With DFCO there shouldn't be any fuel entering the engine at all, its just air with residual fuel from the lower intake, and some exhaust gasses if you have functional EGR. I don't know why it doesn't run hot and/or doesn't knock, I'm guessing its because as the engine decelerates there's no load on it, and it might also be because there's no A/F charge to ignite.
It might cause problems with an automatic Fiero though. There's no DFCO so on deceleration it might depend on EGR to balance out the A/F ratio. Even then there's no load on the engine so I don't think it'd knock that bad, or burn a piston.
Charlie, are you sure EGR only works when the car decelerates? I thought it was supposed to be functional at all times, to add a little bit of exhaust to the A/F mix going into the engine to get better gas mileage and reduce emissions. Does it only work on deceleration because when you lift off the gas some unburned fuel enters the exhaust and having it rerouted to the intake reduces emissions?
Personally, I think EGR is useless. My '86 Fiero passed emissions without a functional EGR valve, and I didn't even have to play with the timing or tune. I'm pretty sure its something engineers came up with to make it look like they're making cars more efficient....when it really doesn't do much of anything, besides maybe lower NOx emissions slightly.