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how much does a bad EGR valve affect MPG?

Discussion in 'Trucks and Trailers' started by Chop Stuff Up, May 24, 2007.

  1. Chop Stuff Up

    Chop Stuff Up LawnSite Senior Member
    Messages: 457

    What the title says. Its been bad for 2 years, managed to get it through inspection. I figure it aint worth the $150 if the truck isn't gonna break down, but the mpg has been kinda sucky lately. Would a new EGR valve fix/help that?
  2. scholzee

    scholzee LawnSite Member
    from NY
    Messages: 130

    The EGR valve basically is open or closed. If it gets stuck open rough idle, stalling poor performance at low rpms. It is usually open at higher rpms and cruising speeds. It actually cools the combustion process by sending exhaust gas back into the engine, but it should close at low rpms and idle. If stuck closed you may hear pinging or detonation from high combustion temperature. The usually get stuck open from carbon deposits. I would remove it and clean it and it may work again, some are easy to get at some hard, what year make and engine. I would say it could decrease gas mileage 2-4 mpg, but the shitty idle or pinging will do more damage, best to get it taken care of.
  3. Eric D

    Eric D LawnSite Senior Member
    Messages: 295

    Chop Stuff Up,

    As Scholzee pointed out there are other factors beside fuel mileage to consider. Simple things to look at to increase your mileage include tire air pressure. If your tires are in good shape I will add 5 psi more then the max rating on the sidewall. This one little thing will buy you more gas savings than any of the junk magnets and other B.S. tricks you will find on the web. Air cleaner, change it on a regular bases. Engine thermostats go bad; change these to allow the engine to come up to full temp. If the engine doesn’t come up to full temp it may run richer then it should due to engine calibration thinking it is still cold. These are just a few things that can help.

    I agree with Scholzee that you should really consider replacing the EGR valve if it is bad. With current gas prices it wouldn't take long to recoup the $150.
  4. Chop Stuff Up

    Chop Stuff Up LawnSite Senior Member
    Messages: 457

    the engine does have a small tap to it and we're lookin at about 35k on this new engine. Its a '92 350 TBI. I've been putting over 1,000 miles on her a week and I keep the tires at 55psi and stay on top of the other stuff such as oil, air filter, etc.
  5. AndyTblc

    AndyTblc LawnSite Fanatic
    Messages: 5,480

    My friend at school, his 04 ford has a late model 03 diesel in it, and his EGR valve was stuck open and it created a vacume in the motor and sucked oil out the exhaust.
  6. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    Wow that's great, so that's my problem!

    I just been taking it real easy on the gas, it sure does ping wildly at higher throttle demands, guess I'll be looking into wd-40'ing this bad boy part, that would explain my 10-11 mpg as well.

    In my case I knew it because the code lights were telling me, but I didn't know what it was or whatever.

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