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did everything still getting 7-8 mpg's what am i missing?

F 150Cobra

F 150Cobra

"Wild HoRsE" Got Torque?
3,642
104
Aruba
Clean IAC new TPS 10.000 less then miles ago .. plugs, wires, coil, cap / rotor, less then 5000 miles a go ..
hmmm i tough it was the bad EEC that i had but with this one its still getting the same mpg so it doesnt have nothing to do with the EEC.. ohh yeah and new watertemp sensor less then 3000 miles ago..:headbang: ... ohh and truck is running a little rich.. and making me poorer :p i can smell gasoline somethimes when i start up or.. at WOT it smokes a little black.
 
Fellro

Fellro

Moderator
Staff member
7,953
361
Iowa County, Iowa
How about exhaust? My understanding is the factory muffler is restrictive, and there is the possibility that you are getting the cat plugged, or the muffler is trying to collapse internally... The 89 I had years ago would get 12 totally empty, hook up so much as an empty flatbed trailer, and it would drop to 8....but it had the factory exhaust, and from what I understand after it was sold, the cat plugged up...
 
F 150Cobra

F 150Cobra

"Wild HoRsE" Got Torque?
3,642
104
Aruba
nope.. i got an 3 inch no cat flowmaster exhuast
 
d-kuzmen

d-kuzmen

Master Ford Tech
2,109
79
Connecticut
Your 3" exhaust mabe causing the problem. Bigger is not always better. Had a truck that I did the same thing to, had no balls and poor fuel milage, come to find out the big exhaust was the problem. Went to 2.5 and was like a different truck. Exhaust needs a certain amount of restriction for backpressure and such. Unless you have some big mack daddy engine under the hood 3" isn't worth it.
 
Lost

Lost

PA Chapter leader
3,288
33
central PA
Check codes but did u do any thing with the 02 ? If you even have 02 or codes that is.
 
F 150Cobra

F 150Cobra

"Wild HoRsE" Got Torque?
3,642
104
Aruba
d-kuzmen said:
Your 3" exhaust mabe causing the problem. Bigger is not always better. Had a truck that I did the same thing to, had no balls and poor fuel milage, come to find out the big exhaust was the problem. Went to 2.5 and was like a different truck. Exhaust needs a certain amount of restriction for backpressure and such. Unless you have some big mack daddy engine under the hood 3" isn't worth it.
Click to expand...

but it was worse!! before the exhuast.. i was getting 5-6 mpg.s before exhuast,, i changed put a costum intake system and exhuast.. and new Fuel pressure regulator and it went what it is today.. and my truck is not gutless:p i barelly press the trottle at 1/4 and it chirps the tires :):guns:
i tought 3" was good for 5.8 and 2.5" was good for 5.0

ohhh i completly forgot!!!! the o2 sensor was NEVER BUT NEVER changed.. the computer doesnt throw a code about the o2 sensor tough.. but i will get a new one.. wich one does my truck use? the 3 wire or 4 wire ones?

bosh or motorcraft one?
 
Last edited:
john112deere

john112deere

caffeine junkie
Staff member
10,807
405
central Vermont
Here's a question (which may have been answered elsewhere...):

How and where do you drive it? I'd about guarantee I could take any old 351 downtown and manage to average 7-8 mpg or lower, any day of the week, by changing my driving style.

Stop and go traffic, jackrabbit starts, flooring it to hear the pipes, all that stuff costs MPGs.
 
F 150Cobra

F 150Cobra

"Wild HoRsE" Got Torque?
3,642
104
Aruba
where i live there there arent any highways... so its mostly downtown... idle in traffic and driving around stop and go... i drive normal.. the tranny shifts at 1500 almost everythime and somethimes i giv it a little more to hear the pipes..
 

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