I know jeeps dont get the greatest mpgs but 11 mpg all stock no lifts. I have a tb spacer on it new plugs n wires new water pump radiator new u joints.and tranny fluid n filter.seafoamed the engine and gas. Itwas geting average 16 mpg then slowly decreased. I also have a new upstream oxy sensor and tires properly inflated 32 psi. It seem since I adjusted my tv cable it started to do this. But I do hsve a irratic idle sometimes maybe tps. And I heard when u replace the up stream oxy sen repkaxe the downstream which I didnt do. And I never reset my ecm. What can be causing my terrible mpgs aby advice will be helpful

 

You should check your iac motor and temperature sensor information on a scan tool. If the temp sensor says the coolant is really cold when it isn't, it causes the em to dump more fuel in to warm it up. The temp gauge in your car runs off its own sensor. The computer runs off a different one. Don't assume your computer is seeing the same value you see.

 

How are you calculating your MPGs? Do you record the gallons pumped at each fill up and divide by the miles traveled on a known good odometer? This is the only correct method (unless you have a modern car that actually measures and calculates it as you drive).

I'm asking because I see lots of people on this forum doing the "fillups per miles" or the "miles per tank" method. This will cause you headaches, because these are not anywhere close to being reliable.

Any method involving your fuel gauge is a lie.


The first method I asked about is the only right way to track your mileage.


If you are calculating it correctly, you have a major problem.

How's the exhaust? If you really burning that much fuel you should see a lot of soot in your exhaust and the engine should NOT be happy.

Have you checked for leaks?

 

I keep a eye on miles per tank & as long as it's close I don't worry.

OP, did you change your cap & rotor button? Either one could be corroded or burnt up.

 

As best I can tell, fuel trims are determined by the following sensors. Coolant temp, TPS, Upstream and downstream O2 Sensors, and MAP. When I replaced my rear O2, my fuel trims went back to 0 instead of about +10%.

 

When was the last time you gave it a completer tune up?

 

Always throwing a wet blanket on everything, Robert.

Spoiling all the fun in the "Let's Pick A sensor" game.

 

That's just the way I am... LOL
I just figured he never mentioned anything about to most common reason for bad fuel economy and everyone is saying it's a sensor.
Ok, Ok I'll join in. I think it need a new engine???

 

Ok. I'll say it. Why a tb spacer? Havent we proven that unless your secretly running a wet manifold they're useless?

 

Unless done recently, I'm with Robert....gotta start with fresh Champion copper plugs gapped ot .035, quality plug wires, distributor cap and rotor. The importance of tuneup hardware cannot be overstated.

Must have at minimum 3 calculated gas mileage samples before you can make any assumptions. Miles driven divided by gallons consumed.

Winter blend fuel, extended idling time, etc. all have an effect on gas mileage.

In the winter (Minnesota), with my bone stock 99 and with an average mix of some highway, some city driving......I'm usually around 15-16 mpg. Definitely drops a notch in the cold weather.

 

Because they're kewl !


And somebody on the Internet said they make, like, 30 or 40 horsepower (er wuz it 3 or 4? Or hundred? I dunno....), and like, totally, radically realign your dilithium crystals and harmonize your califraztle plenum, er sumthin....







Well, actually, if you're running a turbo and water injection, that would be a good place to inject the water, but other than that, they are a well-proven technology for lining the pockets of magic gadget makers. As seen on TV! Call now! Operators are standing by!

 

I've got a tb spacer but only because I got it for free. Though I can not confirm any hp gains, I did get some quicker throttle response and quicker acceleration but that's also combined with my Magnaflow muffler, 2.5" pipe, 784 injectors, high flow drop-in air filter, and bored tb. But I would never pay the $50-90 for a tb spacer.

But we all know that a k&n sticker adds 15hp!!

 

Free TB spacer + time to install it = net loss.

 

But we all know that a k&n sticker adds 15hp!![/QUOTE]


And we all know anything chrome adds at least 15...

 

Kinda like getting a case of the flu!!