Mileage woes....

[timstone]

Ok so to start off I will tell you that I am getting a code 41 (system lean) from my memory codes.

I have within the last 2 weeks replaced the plugs, wires, pcv valve and fuel filter.

I filled up my tank just a few days ago and I have only got about 115 miles out of the tank so far and I have just over 1/4 tank left.

The specs I looked up online say I have a fuel capacity of 19.6g. I'm just giving out a rough number here but say I have 5 gallons of fuel left in the tank because 19.6/4 = 4.9g (per 1/4 tank)

So figuring out the rough mileage. 115 miles / 14.6 gals = 7.8mpg

Seriously...wtf. I really don't think that my lean code that I'm getting should be throwing off the fuel efficiency by this much. That's about half of what I should be getting. I will be filling the tank again tomorrow to get a more exact amount of fuel that I've used but this number seems ridiculous to say the least.

 

[Original_Ranger84]

I would get the lean code fixed and looked at and I bet it will improve it more then you would think.

 

[timstone]

I'd love to...but figuring out that problem isn't always easy. I don't think it's misfiring because I just replaced the plugs and wires unless the coil pack is malfunctioning. I don't have a vacuum pump so I can't really test the MAP and EGR. And the O2 sensors aren't really cheap so I'd hate to replace working O2's just for the sake of trying to fix it.

 

[Big Jim M]

First nobody can tell about milage unless they go from full tank to full tank.. Even then using the same gas pump and parked in the same place and direction is prolly best.
A very high percentage of LEAN CODES come from vac leaks.. Always look for them first..
Was it giving problems before new plugs and wires? If not then think about what was done.. Was a hose accidently pulled loose? Are the plugs gapped properly? Are the plugs the wonderful STOCK plugs? OR did you install the ones that had the bright red boxes that looked so good?
Are the wires installed correctly? Are two wires crossed?
Big JIm

 

[timstone]

First nobody can tell about milage unless they go from full tank to full tank.. Even then using the same gas pump and parked in the same place and direction is prolly best.
A very high percentage of LEAN CODES come from vac leaks.. Always look for them first..
Was it giving problems before new plugs and wires? If not then think about what was done.. Was a hose accidently pulled loose? Are the plugs gapped properly? Are the plugs the wonderful STOCK plugs? OR did you install the ones that had the bright red boxes that looked so good?
Are the wires installed correctly? Are two wires crossed?
Big JIm

I'm going to run it as close to empty as I can but I obviously can't run it dry. As far as the mileage...yea it's always been pretty crappy I've just never really noticed it too much cause I mainly just drive in town and don't take too many long trips like I did with this tank of gas. The plugs I got were the Bosch Platinum Plus...they should be gapped to around .04 or whatever....right?

As far as vacuum leaks...I bought a can of carb cleaner the other day and sprayed all around the intake and nothing happened....I can't hear any other leaks so this leads me to believe it's not related to a vacuum leak.

I don't think the plug wires are cross...I put them back into the separator things when I put them back on...and I also did them one at a time to make sure and put them all back on the correct place...which I also checked with the diagram in the tech library.

 

[chazzone]

You don't really need to run the tank dry to figure mileage. Fill it up. Drive until you use half or more of the tank. Compare the miles driven to the gas used, and you'll be pretty close. If you go to the same place every time, and use the same pump, you can get about the same "fill" every time, and if you compare several tanks, you'll be close enough to get an accurate measure.
I'm not a fan of platinum plugs on engines that were designed for copper. Ford says to use AWSF-42C in the '91-93. Those are copper plugs, and the recommended gap is .054.
I'd re-gap the plugs, if you have them set at .04. That'll have a significant impact on power and performance.
Once you get that set right, you can start looking at the other things that'll affect mileage.

 

[timstone]

Well I filled up tonight. Put in 12.5 gallons and had 146 on the clock....figures up to be around 11.3 mpg or something like that. Happier with that...but still not completely satisfied...I don't see why a V6 gets this kind of mileage.

 

[chazzone]

That's still pretty low. You need to re-gap those plugs, and that should make a difference.

 

[Original_Ranger84]

You sprayed carb cleaner every where over rubber vacuum hoses? Thats bad... carb cleaner destroys or atleast melts? rubber! My dad placed some o rings in a bit of it to clean them off and they came out about 5x bigger then they originally were.

 

[Nhaz]

Propane is a good gas to use for finding vacuum leaks. people don't like to use it . they think its going to blow up in their face. I am sure its possible but its rather unlikely.

 

[timstone]

You sprayed carb cleaner every where over rubber vacuum hoses? Thats bad... carb cleaner destroys or atleast melts? rubber! My dad placed some o rings in a bit of it to clean them off and they came out about 5x bigger then they originally were.

No I just sprayed it around where the intake meets the engine

 

[Big Jim M]

Hoses are a great place to look for leaks. Sons 99 had a hose leak that was really hard to find.. It was a crack in a bend in the hose. When the propane hit that crack, which was hidden from view, the engine really LIKED the addition of the propane instead of air..
Big JIm

 

[timstone]

I'm gonna have a visual inspection of the O2 sensors this weekend sometime....what should I be looking for as far as a good or bad looking one? I have a volt meter but I've got absolutely no idea how to test them like that.

 

[Dweano]

I replaced my sensors awhile ago, (after 170,000km) NOTICEABLE difference, small, but noticeable. I also put headers on at the same time tho. And check your bearings and alignment. I just got those replaced today (to the tune of way too much...) and I noticed it rolls down the road waaay smoother. I can only imagine Ill be getting better mileage.

 

[timstone]

I replaced my sensors awhile ago, (after 170,000km) NOTICEABLE difference, small, but noticeable. I also put headers on at the same time tho. And check your bearings and alignment. I just got those replaced today (to the tune of way too much...) and I noticed it rolls down the road waaay smoother. I can only imagine Ill be getting better mileage.

Pretty sure my alignment is perfect...last weekend when I took a long trip I even let go of the steering wheel completely while driving 70 and it stayed straight for well over 100 feet.