So I usually run the tank down before I fill. I zero out the trip odo each time. I usually have about a gallon left when I ht 320 miles. which means I have about another 15 miles in it.
Yesterday i was going to get gas after shopping It was at 295 when it ran out in a busy intersection. Some kids helped me or i would have been screwed I had no phone.
What would cause that drastic a drop in MPG's in one tank? There were no signs of decline or poor running. I did cap wires plugs rotor in the last 1K and not long before that I put in a new O2 sensor. I haven't looked at it since I git home yesterday after noon. Oh yea 22gal tank

 

Whew.

I was wondering what kind of Dakota got over 30 MPG ... but you mean 30 miles in a TANK. About 1.5 miles per gallon.

That's not uncommon.

Possible causes:

Low tires.

Different gas formulation.

Longer idles.

Traffic Jam or two. (Traffic Jam! Serve on Toasted Idiot with a Helping of Inyer Butter! Yum!!! ... Sorry.)

Clicking off a bit sooner than you expected last time.

Cracked vacuum line *razzle frazzle* guy who redid my transmission broke FOUR of them!! Three with stubs I could cap, and of course they're OK now; the fourth one was broken AT the vacuum solenoid and is apparently the line to the evap canister. *razzle frazzle grump grump*

I'll add that you should never, EVER let it get down to the 1 gallon mark; the fuel is supposed to help keep the fuel pump cool, and it's in the air that high up. Besides, what happens if you get stuck on the interstate behind a 3 lane accident, when there's only 3 lanes, at 5 PM? Yep, dead truck.

I'd start looking for gas at 200 miles, and put 240/250 as my "GOTTA GETTA TANK NAOW!!!" mark; I mean, your cousin and mine, Justin Case, would really appreciate it!

RwP

 

Oops. I never did well in grammar.
Thanks Ralph. The air cleaner is good, i looked today and oil and filter are also new in the last few months. I haven't checked the tires. I think the rebuilt injectors I put in 4 or 5 years ago probably should be replaced with new. The website is now called Motor Man I think it was a different name then. Link still woiks?? Might be the gas and I did get stuck behind some nice folks who don't know how to drive but that wasn't for very long. The guy behind me when I ran out commented he could smell my gas. That makes me thing the injectors might be a factor and since it is cool out the 180 thermostat might have something to do the O2 sensor and the pcm reading of need for fuel.

 

Heh. Yep, that's a side effect of using a 180* thermostat - it runs a touch richer.

The O2 sensor is another choice.

I don't think I'd swap injectors after 4 or 5 years, without other evidence that they're failing; they tend to be bog reliable for many, MANY thousands of miles and years.

I've bought from Motor Man; that's one of my links ( five-oh motorsports is another; but my next injector purchase will probably be Deka 80lbs for the Cougar, since that's what the guy doing my tuning likes.)

RwP

 

Th O2 sensor is pretty new. I'll check the tires and stick the 195 T back in if I can find it to see what it does. I'll probably have to go back to the 180 when AC weather comes.

 

Nope, keep the 195 in there. You won't notice a difference in a/c with it and your computer will get out of "open loop" mode. That will slurp fuel like you wouldn't believe. I don't like to run below 1/2 a tank. If a storm comes through and power is off, you won't get fuel.

 

One other tip. Fill up when the gauge is at 1/4 tank. Your chances of running out are very slim and it will cost less to fill. Running until you only have aprox 1 gallon left is just crazy IMHO. There are a lot of factors that can easily change your MPG one or two MPG. Why risk running out.

 

I probably know better but that is what I was doing.
So I pulled out the 195T from the cabinet. Let me first say I went with 180 because it was running hot enough to scare me. Turns out I may know why now. the 195 T that I removed does not have the hole to allow air out! I'm guessing here but it seems likely that I had trapped at least some air after I did the plenum WP TC etc. I think I'll just go buy a new 195T with the breather hole instead of drilling one.

Edit- Just looked at RA and none of the T's have breather holes!?? Am I wrong in thinking there should be one? It, the flat surface outside where the valve is, usually has a piece of metal expanded on each end like a barbell through it I assume so it doesn't plug up.
edit2- How much movement should I see? I out the 195T I have in a cup and poured just boiled water over it. I saw some tiny bubbles but no movement. I did it twice. I've manually depressed it while it is still hot and it moves less than 1/16. Is that the range? Seems like even with pressure behind it not enough water could get through. It also moves against teh spring which has me questioning whether or not the spring should be on top or bottom?

 

The computer goes out to closed loop once the O2 sensors warm up, so the thermostat won't affect that. I've been running a 180 t-stat in my 3.9 and got about 12-13 MPG daily driving, but I have a bit of a "lead foot" anyway, and got about 16 MPG on the highway. The 195 to 180 thermostat doesn't affect it very much, maybe 1-2 MPG difference?

 

I got 17 or 18mpg on the first tank when I did the plenum etc. I went to the 180 around then and I have been getting <15 since. I'll take a chance on the 195. Seems like 1 or 2 mpg is from 22-44 extra miles per tank. That is a lot to me.
I called NAPA and they told me they had a it with the jiggler valve. When I got there they didn't have it. I went to AZ and the guy found me one Duralast 15359DLG. I think he said it was fail safe.
I think my 195T was bad. When I asked I was told it should move more so I pressed harder and it did move. The new one I pressed moved a lot easier. I figure that may also have been part of the problem.