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Poor MPG

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Morris

Morris

Yoda
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My 1500 is getting what seems to me very poor MPG. Currently I am getting about 26-27. But the mpg seems to be slowly falling every time I check it. I am not getting any glaring signals from the engine to indicate the source for my poor mpg. Car runs great, has great power, plugs look good, vacuum signal is strong, and the Wide band 02 sensor I have installed is not giving me any conspicuous readings.

Can anyone give me some advice on how to trouble shoot this problem?
 
I would look for a pinhole leak in the fuel line. It would get worse over time.
 
Some of it goes back to the 1500 itself.

I'm guessing you have a stock cam, which is designed to promote an "ERG-like" effect that can diminish fuel consumption.

Also, check timing at 4000+ rpm. You should have around 30 degrees BTDC at that speed (you don't need a degree wheel...just make a mark at around 30 BTDC and put a timing light on it).

And what is your wide band showing? You can cruise at a fuel ratio of about 14 or 15 to 1 easily, when not under a heavy load.

Also, stop peeling out so much!! :jester:
 
Nial, if I set my timing to 30btdc, I get pinging under low rpm load. Any thoughts on what that is all about?

Currently I am running a max advance of 26btdc at wide open throttle. I run 93 octane and my compression ratio is roughly 9.5:1. The spark advances to I think 40 at cruise. Also, my advance curve maxes out at 3000 rpm. Do you recommend that I have it max out at 4000 rpm?

My wide band shows about 13.5 under load and 14.3 to 15 at cruise. Kinda depends on what mood the car is in best I can figure.

Lee, I have looked and looked for fuel line leaks and have found none. Any thoughts on how to find them other than eyeballs, nose and fingertips? The nose occasionally smells raw gas, but the eyes and fingertips cannot corroborate that evidence.
 
mine was leaking gas from the
hose on the jet on the front
carb.....check ur carbs for
wet areas............z
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Also, stop peeling out so much!![/QUOTE]

Honestly, I don't drive very aggressively. The most reckless thing I do in my car is draft big trucks. So by my figuring, my driving habits should be giving me much better mpg.
 
Morris said:
Lee, I have looked and looked for fuel line leaks and have found none. Any thoughts on how to find them other than eyeballs, nose and fingertips? The nose occasionally smells raw gas, but the eyes and fingertips cannot corroborate that evidence.
Click to expand...

Cheapie glow-in-the-dark kit... they make fluid you can add to various systems that then shows up under black light. Very CSI, but it might work well? Pretty sure they have a version for the fuel system.
 
By the time you're losing enough gas to notice a drop in mileage, you should be able to see it as well as smell it.
If no puddles form when the engine is running, then you must be burning it one way or another.
If your plugs look good, maybe you are just getting the "tune" to where it should have been all along. I used to get over 30mpg with the turbo 1275, but I later learned it was lean at many points. AS I've continued tuning, the car performs better and better but the mileage has slowly crept down accordingly. The plugs were whitish when the mileage was great and now a bit creamish since the tune is dialed a bit richer. The wideband sensor has shown me what the A-series prefers as far as AFR, and a rich idle is a must, but I'm currently set for 16.0:1 for deceleration, 15.0:1 no load,
14.7:1 light load, and changing from 14.2:1 nominal load down to 12.4:1 at 10lbs of boost.

Glen
 
I once registered 14 mpg on my MGB. I got to looking and the retainer ring on the fuel pickup tube assy was loose and gas was slowly dripping out of the tank. I park on grassy or dirt areas, so the leak was neither seen nor smelled. Just a thought.
 
Lots of things can cause this. I'd check;

plug wires, anything in the ignition system, small
hole in fuel pump diaphram, partially clogged muffler/cat converter

I've experienced all of there failures over the years, and
they can come on slowly.

Good luck!
 
One other thing that is not discussed much is the crappy gas we are being sold this time of year and even more now with the prices rising. That ethanol blend just doesn't produce what regular gas does. Yes, our cars run on it but there are side effects. One being less gas milage. Our Honda Pilot has seen a large drop in gas mileage since the "summer blend" has hit the area.
 
Oh gosh, I forgot about that junk. For sure, for sure.
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]One other thing that is not discussed much is the crappy gas we are being sold this time of year [/QUOTE]

Good point! My mpg has dropped 2-3 miles since the summer gas rolled out.
 
Morris said:
Good point! My mpg has dropped 2-3 miles since the summer gas rolled out.
Click to expand...

That is your answer.
My daily driver has lost 4-5 MPG with the switch to the summer blend.
My question with this stuff has been, how can my car be polluting less when I have to burn more fuel to go the same distance? :crazyeyes:
 
It is fairly well documented that it takes as much energy to produce ethanol as is returned when it is used as fuel. Not to mention the added price we are all paying for most of our basic FOOD. Not only because the corn is being used as fuel instead of food, but because corn is being planted instead of other crops, making the other crops more scarce! .. History will take a dim view of this hysteria...

Studies on E-85 show that although the cost per gallon is less, the fuel mileage is also less--- so much so that it is MORE expensive in terms of $$$ per mile. . ...
 
Don't take this thread into politics, please. Basil has very politely asked us not to. My point in mentioning ethanol is that many people are thinking something is wrong with their cars and are not aware of the impact of the fuel issue.
 
Bingo, give that man a prize.
 
Silverghost said:
Don't take this thread into politics, please. Basil has very politely asked us not to. My point in mentioning ethanol is that many people are thinking something is wrong with their cars and are not aware of the impact of the fuel issue.
Click to expand...

OOPS... i edited of political content.
 
I don't see how this changes for people in colder regions.


Despite the blend change, I always get better mileage in the summer than the winter. This is across multiple vehicles and engine sizes. They were all FI though, no carb'd cars.

Reason being the air density. Cold air = denser air, therefore more fuel is required to remain stoichiometric. In the summer, the less dense air = less fuel required. Also takes much less time to warmup and enter closed loop.
 
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