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EGR valve - fuel mileage?


302Z28
09-15-2011, 09:59 AM
I have a '92 metro that was getting 50+ mpg a few years ago when I drove it. The car has since been given to my daughter and she started complaining that the best she could get was around 39 - 40 mpg. A few months later, it burned an exhaust valve. Upon dis-assembly, I found the EGR valve was not working - passages plugged. I know the EGR caused the burned valve. Could it also be responsible for the lousy fuel mileage?
Thanks,
Ray

BrianAlex
09-15-2011, 11:44 AM
I have had 2 cars with clogged EGR valves and the mileage was a bit off on both but in your case I would first suspect that your daughter's driving style and the possibility that she was driving around on 3 cylinders would be greater factors in play.

Woodie83
09-17-2011, 06:21 AM
All Metros burn valves. The ones with clogged EGR, the ones with working EGR, and the ones that came from the factory without EGR. A clogged EGR might speed up the process a bit, but that's just theory, and one that I'm not sold on.

Also theoretically, EGR should increase gas mileage, but it's not going to be any huge amount of increase. I guess 2 or 3 mpg. Unfortunately, the same cars that got EGR also got ridiculously late ignition timing. Bumping your timing up from the factory set 5 BTDC to a more reasonable 10 BTDC will do far more to increase power, mileage, and valve life than anything else.

It's more likely that your daughter has bad driving skills from a gas mileage perspective, and the engine has been down on compression for while, it's a slow process until it gets down below 150 psi, then it starts going faster and faster because you're over stressing the stronger cylinders to make up for the weak one.

Woodie83
09-17-2011, 06:24 AM
Oh yeah, I hope you did rings when you did the valves. Doing the head alone almost always creates an oil burner, and burning oil will burn your new valves in no time at all.:runaround:

atjunkie
09-25-2011, 07:28 AM
I lost milage after cleaning the egr!!

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