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Gas mileage question for guys with Ford injectors

What would cause a big loss then after a swap?

I have 90 with a 4.0 in it.

Before the swap I would get 300ish per tank and now I get about 200ish per tank.

I have had the swap for about 6 months and its consistently 200ish per tank.
 
19# I think? They are the yellow top ones. Now you have me wondering. I hope they are the 19 # cuz that what I wanted.
 
poomero said:
19# I think? They are the yellow top ones. Now you have me wondering. I hope they are the 19 # cuz that what I wanted.
Click to expand...

Post up the number that is on them. Someone will be able to tell you.

Don't eliminate the possiblity that coincidentally something happened to fail/change on or about the time you replaced the injectors.

I like to, at least once in my older Jeeps' lifetime, unplug and spray out with a good electronics cleaner, every engine management connector in the engine bay before plugging them back in. Bad connections frequently disguise themselves as faulty components to the unsuspecting.
 
I am not ruling that out. I am just trying to track down and replace what could have gone wrong. I am swapping the o2 sensor tomorrow. Today I did the cat and a muffler. I will also change plugs, cap and rotor tomorrow.

What else should I be checking on???
 
Air filter, clean the throttle body & all attached sensors.
Any strange starting / running / idling conditions before or after the injector swap?
Always possible you have a leaky injector. You can look at the intake manifold for signs of gas. If it is leaking through the injector, instead of from, you'll see hard cranking at startup esp. from warm.
Anything else change in the last 6 months? gears / tires / lift / roof racks
and most of all
driving habits?
I notice a 75% gain in fuel economy when I take one good long highway trip over a tank of gas.
 
No additions to the jeep that would change gas mileage.
New air filter.
New TPS adjusted right.
sometimes when it is warm and i let it sit for 5 min. or so it wont start. If restart it right away it will be good. If I let it site for more the 10 min. or so it will also be fine.

I just changed the o2 and the cat to see if that will help with the mileage.
 
They were cleand and flow tested. I changed the O2 and I think that may have helped but I wont know for a few tanks of gas.
 
Well, for most of that time there was the "winter blend" fuel. So that probably did not help.
I am running the set of 19# injectors that I got from you and have seen a 1-3mpg increase, other than with the winter fuel. My idle definitely improved.
In the last couple months I installed a 60mm TB from strokedjeep.com , definitely worth the 90$
 
The hard start after 5 minutes, combined with poor MPG, AFTER doing injectors, makes me think you have an injector that isn't closing all the way.
When this happens, fuel continues to leak from the rail into the cylinder after engine shut off. The extra fuel in the cylinder keeps makes the condition too rich to start (or just a rough start)
Eventually, though, the pressure in the rail is drained and the fuel leaks down past the cylinder rings - so the engine will start again.
Of course, gasoline is a solvent and will ruin the engine oil. So, there is that.

I suspect you have a leaky injector, dude. Get a fuel pressure guage and check pressure at the fuel rail. with the engine cold, engine warm and recently shut off, etc. You don't want to see the fuel pressure at the rail dropping very quickly after you shut down the engine. There is a check valve in the fuel line, for one thing, and hte injectors should be sealed for another.
 
Johnnie Walker said:
Well, for most of that time there was the "winter blend" fuel. So that probably did not help.
I am running the set of 19# injectors that I got from you and have seen a 1-3mpg increase, other than with the winter fuel. My idle definitely improved.
In the last couple months I installed a 60mm TB from strokedjeep.com , definitely worth the 90$
Click to expand...

Im Glad they worked out for you.

I think My issue was caused by a bad O2. I changed it out and now it runs like a champ.
 
yossarian19 said:
The hard start after 5 minutes, combined with poor MPG, AFTER doing injectors, makes me think you have an injector that isn't closing all the way.
When this happens, fuel continues to leak from the rail into the cylinder after engine shut off. The extra fuel in the cylinder keeps makes the condition too rich to start (or just a rough start)
Eventually, though, the pressure in the rail is drained and the fuel leaks down past the cylinder rings - so the engine will start again.
Of course, gasoline is a solvent and will ruin the engine oil. So, there is that.

I suspect you have a leaky injector, dude. Get a fuel pressure guage and check pressure at the fuel rail. with the engine cold, engine warm and recently shut off, etc. You don't want to see the fuel pressure at the rail dropping very quickly after you shut down the engine. There is a check valve in the fuel line, for one thing, and hte injectors should be sealed for another.
Click to expand...

Thanks for this info. Mine has been doing a similar thing since I bought it, although mine always starts if I push the gas down some, so I was going to do a basic tune up, well mainly just an air filter and fuel filter since the PO had just did plugs, wires, cap and rotor. I was also going to connect my O2 to a DMM to see if it was showing bad readings. If money is right next month I was planning to do the ford fuel injectors so hopefully the new (refirbished) injectors cure the problem along with the rest of a tune up.
 
poomero said:
Im Glad they worked out for you.

I think My issue was caused by a bad O2. I changed it out and now it runs like a champ.
Click to expand...
What size is the "nut" on the O2 sensor?
 
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