Hi, Guys! i've been searching in the forums about the EGR valve, because my engine light came on and in autozone, the guy told me that my EGR valve was the the cause. So I live in Florida, so not emissions tests are required by law; my question is about if the EGR valve malfunction would have an impact on the MPG. I read a tread about the EGR valve not having an impact on my miles per gallon. Somebody said here that only the new oxigen sensor and a tune up can improve our MPG. I am asking because my MPG are a little poor right now so i was thinking that my bad EGR valve might have something to do with it.

thanks for your replies.

Doubtful, EGR stands for exhaust gas recirculation.

Your MPG will be effected but slightly, in a internal combustion engine you have a few things going on. First you suck in air the two atoms we desire are Oxygen and Nitrogen. When fuel is prayed into the chamber then compressed the spark plug ignites the chemical reaction between Oxygen and the fuel. The fuel consist of Carbon Hydrates, the Carbon and Oxygen combine together to make Carbon Monoxide or Carbon Dioxide ect.. this fusion of atoms creates a large amount of energy in the form of heat. Nitrogen a inert gas then expands at a rapid rate, the nitrogen is what pushes down on the piston.

The valve simply just returns some of the exhaust back into the chamber to use some of the oxygen and nitrogen maybe some fuel, since N/A engines and can't force all the air they want they want into the engine like turbo/super chargers, we have to come up with ways to get the atoms we need.

To answer you question if the exhaust is not going back into the chamber then your are not getting you maximum power of your pistons therefore more fuel needs to be used to get the same power you expect.

Well i just found this in one of our treads here at 6GC




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QUOTE (Kwanza26 @ May 9, 2010 - 3:41 PM) *
All the stuff about fuel economy at cruising speed is irrelevant to the EGR system. Learn how it works before you go off on a tangent.


That raises a question for me - and it sounds like you can answer it/clear it up. I thought the EGR only actually came on at cruising speed (i.e. about 50 mph). So my question is, how would a faulty EGR affect stop-and-go driving if it doesn't activate until you hit 50?

Reason I ask is that I've been fighting with my friend's EGR on his Prizm (4AFE). We had to get it through DEQ, and after replacing the EGR w/no luck on the CEL, I finally just took it to a parts store and had the CEL reset, at which point we drove it to DEQ (about 6 miles) and kept it under 40 mph so the EGR wouldn't trigger and the CEL code would stay clear long enough to get it through DEQ. (Illegal, I know. Desperate measures, ya know...)

In his particular case, the CEL or bad EGR hasn't affected "performance" or gas mileage at all. I know on other cars though, a CEL would throw it into "safe mode" and make the car run like crap and get horrible mpg. Does this just not really apply on our particular cars (or variations thereof)?

Reset your ECU, and see if the CEL comes back up.

When it does, run the test to find the code of what it is.

If it is certainly your EGR, there isn't much to the system from my experiance.

Remove it and inspect it, find another at a yard.

>

Im just finishing up a thermodynamics course, and we spent 3 weeks on combustions. the point of egr is to lower cylinder temperatures and therefore reduce nox emissions. So the impact on mileage will be miniscule. The biggest problem with a faulty egr systems comes with drivability issues. If you're EGR is stuck open then the engine can get choked with exhaust at low speeds and idle

Take the end of a screw driver and smack the top of the egr valve a few times...should get that code to go away.