Bali26

Hi guys,

I replaced my o2 sensors last week but im still getting 11 miles a gallon. What should i try next in the order of probable cause? (plugs and wires are new, there is no CEL)

I drive only 4 miles (city) to work and back a day and its below freezing. Is that why?

Thanks

nawls400

i'm gettin about 12 mpg doin about a 4-5 mile trip to school and back everyday, so it sounds like it's just these very short trips that is giving us bad mpg, because i was wondering about this for a while as well and since we seem to have similar situations so it sounds like this is the case

jcrome04

Driving from Salt Lake City, UT back to Sequim WA (960mi) I averaged about 28mpg, with horribly neglected plugs and air filter. My daily commute is about 15miles to work, Less than 5 around town, 15 back home, then if i decide to hang out with some buddies or not. I've been at about 18mpg average. Wouldn't mind trying to better it....Would doing the BFI intake help a bit?? and/or some Seafoam?

Bali26

So am I getting normal mpg?

I think i need to clean injectors next. (with seafoam)
But the thing i dont understand is:

If the injectors are blocked, it should let in less fuel in thus giving better fuel economy but lower performance. Same for fuel filter. It will let LESS fuel in, not more. I know i'm wrong but dont know why exactly.

sonyman

You're wrong because combustion is a much more delicate process than less fuel = more efficient. There is a fine line between stoichiometry and inefficient motoring. To top it off, the engine always expects to be able to receive enough fuel. Fuel is the independent variable; air is the dependent. You need air to burn your fuel, not fuel to burn your air. Not enough fuel results in poor stoichiometry and therefore inefficient combustion.

Bali26

So fuel is the independent variable....If there is not enough, engine will reduce air intake thus reducing power. How in all this am i using up more fuel? (sorry im a little slow)

And how about my mileage? Is it normal considering the short drives and what should i check next? (I have new sparks, o2 sensors, checked spark wires, cleaned air filter, new pcv, no warning lights, starts ok, runs ok)

sonyman

Fuel is the independent variable in the sense that you want to adjust the air intake to burn the amount of fuel, on paper. In practice it works a bit differently, since on a car the throttle actually modulates air input. The engine runs poorly when it can't get enough fuel because it expects to have the necessary fuel in the first place. The engine always injects the same amount of fuel into the cylinders each time the ECM pulses the injectors. When more air is allowed into the intake plenum, the engine compensates by increasing the injector pulse width, thus increasing fuel delivery. It will also have to pulse the fuel injectors more often as the speed of the engine increases. So I guess I should have said that on a car, in the real world, the fuel-air relationship is reversed.

What I think you need to do is to fill up your tank, go for a 25 mile highway run, then fill up again to calculate gallons used for that given mileage. 4 miles per day isn't exactly contributing to good mileage, but a highway run should yield numbers with fewer uncontrollable variables.

Bali26

Ahh I didn't know that.

I guess its time for a roadtrip...Thanks

LiCelsior

iTrader: (32)

sony a question for you...so if the engine is not getting enough fuel will it make the car jerk when applying acceleration? like what i mean by jerk is that it stutters or something and makes the car accelerate very slow.

sonyman

That's certainly possible, but not the only plausible cause. Make a new thread with more information so you can get input from multiple people. I would need more information myself in order to provide any useful input, such as how much acceleration causes the condition, if it always exists, and so forth.

LexLS

Here in Minnesota I've noticed that I always get considerably lower MPG during the winter months. I searched a bit and found this: http://www.startribune.com/cars/11354696.html

For the last month or so it's been in the teens or lower and I get around 240 miles on 3/4 of a tank. In the warmer months I typically get 300 miles on 3/4 tank or more. So that's about a 20% decrease in MPG during winter.

Did you ever get your mileage up drifter?

93LSexy

HOW THE HELL DO YOU GET 26-30 MPG ON HIGHWAY??? my 93 gets 360 miles per every 20 gallons. I do 70/30 highway/local... I do step on it from time to time and do around 80 on the highway. that's a 18mpg on average. I would LOVE to be able to get 26-30 MPG on the highway. Last week, it costed me $75 to fill up 21 gallons of 93 premium!!! and i burn that up in just 5 days. I have a brand new filter, changed the oil, plugs and wires less than 20K miles old. Should I look into the EGR delete or new O2 sensors?

jcrome04

The awesome thing too is I was averaging probably 85=90mph through Idaho, thats when I got about 26mpg, Then From Ellensburg, WA to Sequim, WA I got 28mpg. Anverage speed about 55-65mph. I was SHOCKED when I filled up and crunched some numbers. I could have easily gotten 30+mpg with new new plugs and air filter!! Here's a photo of the air filter just to show you how neglected my baby was!!!



the cover to the filter had a ton of sand sitting in the bottom! heheh leaves dirt not to mention a few bees!

Bali26

Also if your engine is not getting hot enough, u will get bad mileage. Ecu switches over to closed loop only when its gets operating temp. (from article above)

My temp gauge never goes over 1/4 mark. ( maybe fan is always running instead of shuting off, or maybe thermostat )

sonyman

Bali26, note that I made a correction to my post above as I had forgotten about how injector pulse width factors in. Just so you aren't misinformed.