Lost mpg
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New User
Joined: Nov 2012
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From: Mi
Lost mpg
Ok so this is what i did .... I got a 94 E350 it was running rough so i gave it a tune up , changed 2 bad injectors , changed both o2 sensors & added dual exhaust.
Now before i changed the O2 sensors the exhaust was real strong & i got around 11mpg . Now that i hooked them up i get around 5mpg.
What did i do wrong ??? Feel like im going backwards instead of forward !
Hope someone can help me !!!
Now before i changed the O2 sensors the exhaust was real strong & i got around 11mpg . Now that i hooked them up i get around 5mpg.
What did i do wrong ??? Feel like im going backwards instead of forward !
Hope someone can help me !!!
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Joined: Feb 2007
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11mpg sucks. 5 mpg sucks much worse. With any engine?
Sorry, but "the exhaust was real strong" does not compute.
Have read plenty of stories about Ford Truck Enthusiasts investing serious cash to modify stock exhaust system, only to complain of significant MPG loss & performance issues. Seems that big changes in exhaust back pressure throw off the computer, messing up FI.
Have read plenty of stories about Ford Truck Enthusiasts investing serious cash to modify stock exhaust system, only to complain of significant MPG loss & performance issues. Seems that big changes in exhaust back pressure throw off the computer, messing up FI.
Elder User
Joined: Mar 2012
Posts: 711
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From: Outside of Memphis, TN
You have discovered how dumb the EFI is on these speed density trucks/vans! The ECU literally just guesses almost everything. The only real inputs it has is the MAP sensor, engine temp, intake temp, throttle position, transmission position and o2 sensors. If any of these are wrong, the ECU gets confused and goes into limp/even more guessing mode. I'd scope those o2 sensors you installed to see if they are providing crap signals/bad out of the box. I'd also check those 2 injectors you replaced to see if the replacements are bad and just pouring fuel into the engine.
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From: Mi
I wonder if the dual exhaust is causing the problem . If i unhook the O2 sensors my mpg gets better . I really dont like electronics !!!
My 87 suburban 350 /4 barrel got around 15mpg & it weight around 5,000 lbs . My parents had a Lincoln town car that when we put the dual exhaust on it it ran ok but didnt have much mpg .
Now im wondering what i should do ! I like have true duals but i guess some vehicles aren't designed to run that way . 351w has alot of power
My 87 suburban 350 /4 barrel got around 15mpg & it weight around 5,000 lbs . My parents had a Lincoln town car that when we put the dual exhaust on it it ran ok but didnt have much mpg .
Now im wondering what i should do ! I like have true duals but i guess some vehicles aren't designed to run that way . 351w has alot of power
Elder User
Joined: Mar 2012
Posts: 711
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From: Outside of Memphis, TN
Disconnect the second one. It shouldn't be in use on standard 48 state emissions calibrations and might be causing hell.
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From: Mi
When i only run one the mpg still sucks ! I tried only runnin one & i was only gettin around 5 mpg. (No o2 sensor's hooked up ....) Strong fumes coming out of the exhaust & i get around 11+ .(Hook 1 or 2 up) I cut the fumes down & i get around 5 !!! Wth! I dont understand !!!!
Im so confused on what to do !!!!
I swear id rather have a Holley 4 barrel !!!!
Im so confused on what to do !!!!
I swear id rather have a Holley 4 barrel !!!!
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