Fuel consumption - 2005 Tucson

I have a Tucson, 2005, automatic, 4WD, 6 cyl. Though I got a good deal when
I stumbled on a used one (3300 miles) and bought it at a good price. But
mileage has been awful. I've put 2000 miles on it so far, and mpg has
dropped off from 13 mpg to current 10 mpg... I had only one lengthy freeway
run, about 200 miles, and even then only did about 17 mpg.

Does anyone have any thoughts? I took it to dealer; mechanic says there is
nothing wrong with car, but I disagree. I don't know how to approach this
problem mechanically.

Judy

 

Chances are, the technician's right. The technician has the capability to
see the computer's data stream and make sure everything appears correct.


As to what you can do:

Drive the vehicle easily. If your in an urban area, this will be
difficult.

Make sure the vehicle engages all 4 forward gears and that the engine
seems to run well.

 

Chances are, the technician is wrong. Just because he or she can read
the data doesn't guarantee the data is correct.

Your Tucson has an EPA rating of 17mpg city/22mpg highway. Real world
mileage is always a little less. But not 10 mpg. Carefully measure your
gas usage and odometer readings. If you really are getting only 10 mpg,
then there is something wrong. Me, I'd pull a spark plug or two to see
if its running rich -- maybe the onboard chip has got the air/fuel mix
wrong, or a fuel injector is bad, or ... you get the idea.

For the tech to read the data and shrug his or her shoulders and say
nothing is wrong is being a little lazy, IMHO.

 

Thanks, that's how I feel. The Hyundai tech may be treating this somewhat
cavalierly. I will have to go back to the shop. I do treat my car well,
although it is used mostly in city driving. But I don't have either a heavy
or a light foot on the pedal. I know how to drive.

Judy

 

Folsom said:

Me, I'd pull a spark plug or two to see
if its running rich -- maybe the onboard chip has got the air/fuel mix
wrong, or a fuel injector is bad, or ... you get the idea.

For the tech to read the data and shrug his or her shoulders and say
nothing is wrong is being a little lazy, IMHO.
-----------------------------------------

I think you fail to understand what the technician can see and interpret.


A good technician can drive the vehicle and tell whether it has the proper
amount of power, whether the transmission or clutch is slipping, and
whether the transmission shifts through all the gears properly.

A good technician can look at the data stream and see whether the vehicle
is running rich; he doesn't need to pull a spark plug to do that. In the
data stream, the technician will see values for the oxygen sensor readings
and the fuel trims. The oxygen sensors, combined with the programming of
the engine control module, control the fuel mixture. So, to determine if
the vehicle is controlling the mixture properly, the technician looks to
see if the front oxygen sensors cycle properly. The technician looks at
the fuel trims to see that the computer isn't unexpectedly providing
significantly more or less fuel than expected for the given operating
conditions.

Excessively large fuel trims (in either direction) indicate problems with
oxygen sensors, unexpected air or fuel leakage into the intake/combustion
chamber, or possibly other problems.

And this isn't the limit of the data the technician can see. A good
technician doesn't just read the data; he interprets the data to see
whether it appears correct. So, no it's not lazy. It's the technician
performing a task to approach a problem in a logical and efficient manner.
Suppose you were footing the bill? Would you want to continue paying the
technician to pull stuff apart until he found something? How much would
you spend without the technician finding anything before you were willing
to give up? Would your engine be in pieces on the floor? The reality is
that checking the data stream, combined with a test drive, *is* an
effective way to determine whether a vehicle is running properly.

I give some kudos to this customer. She actually knows her fuel economy.
Most of the customers who complain about their fuel economy have no idea
what it is and many are confused about how to compute it. It's sad,
really. And I agree this poster's fuel economy is low enough to give some
pause. But I know neither the customer's driving style nor driving
conditions. It's enough that I'd look pretty hard at all the data. I'd
also want some more information regarding what is involved in a typical
daily trip for this customer-- especially if I found nothing wrong. Does
she warm the vehicle prior to starting a trip? How short are the trips?
In what sort of traffic are the trips taken?

Just like any other problem, this one needs to be aproached logically in
order to find a resolution.

 

My 2002 Sante Fe was getting 13 mpg City. Turned out to be BP
gasoline! I switched to Marathon or Shell & get 22 City/ 30 Hwy & its
an automatic! SO good gas at 97 octane since high test isn't needed
wins.

I was also told by my tech never to fill up in the rain, and to run it
down to 1/8 of a tank to fill & that gives me correct mileage which 1/4
tank doesn't. So try all of this & let us know.

 

<<Does anyone have any thoughts?>>

Try driving on level ground, at a steady speed, where there is no other
traffic around. Take foot off gas, shift to neutral, and observe how
quickly the vehicle slows down. If it slows too quickly, something may
be dragging (i.e. brakes) or out of alignment (i.e. wheels).

John Cowart

 

<<Does anyone have any thoughts?>>

Are you one of those people who "rides" the brakes? Just wondering...

John Cowart

 

Well, 97 octane is pretty high test if you ask me. Where I live 87 is
typical and 94 is about as high as you can find short of aviation or
racing fuel.

What is your tech smoking? Filling up in the rain? Not getting correct
mileage at 1/8 tank vs. 1/4? What a bunch of hogwash. You won't get
correct mileage just checking one tank in any event. You need to check
at least five in a row to have any assurance of a reasonable average.
And if you check several in sequence, it doesn't matter if you fill up
at 1/8, 1/4 or 1/2 level. Any little over or underage on one tank will
be factored out by the next tank.


Matt

 

Scientifically speaking, the more fuel used, the less error will be
introduced by filling variances. I.e.-- there's a significantly larger
amount of fuel used than the difference in how full the tank is based on
differences in auto shutoff, vehicle slope, and other factors.

But you're correct on taking several samples, regardless of amount of fuel
at fill-up. This will minimize error as well as make aberrant values stand
out.

 

Nice points, John. I usually check for brakes dragging by coasting to a
stop in neutral on a slight upward incline. The vehicle should smoothly
reach a stop and begin rolling backward-- it should not jerk when the stop
is reached.

The chances of getting a shop to put the vehicle on the front end rack to
check alignment (without ponying up at least an authorization for the
typical alignment charges) are small. Hyundai won't pay for the alignment
if the values are within spec, so the dealer will be looking to charge the
customer for their effort if there's no problem. Look for front or rear
tires wearing on either the inside edges or outside edges and make sure
the steering wheel is centered. Either the wear or the steering wheel
issue indicate a likely alignment problem, but absence of these issues
(especially on a new vehicle where tire age is minimal) doesn't mean there
isn't a problem with the alignment.

 

True, if you are only checking that one tank. However, checking one
tank isn't statistically significant to begin with so making an
untrustworthy number just slightly less untrustworthy isn't really
meaningful.

And when you do this, don't calculate each tank separately and then
average them as that isn't legitimate either. Add up the total gallons
consumed and divide that into the total miles traveled across all tanks,
being sure that your first mileage point was a full tank. Do this for
five or more consecutive fill-ups and you will get a reasonable estimate
for average fuel economy during that time.


Matt

 

No, I don't. I try to get up to speed as quickly as practical, given what
traffic is doing. About 80% of my driving is in the city, where the limit
is usually 35 mph, the rest on the freeway. My previous vehicles delivered
EPA or better until they were very old. I am not the type to jump out at
red lights or try to beat the light; it's a waste of time. I am plain
disappointed that this car is not deliverying mileage anywhere near the EPA
figures.

Judy

 

After reading more of the thread I still think there's something wrong
for you to get 10 mpg.

As I mentioned in my prior post, I'd check the spark plugs. The tech
says the computer says everything is OK. A visual inspection of the
plugs is an independent check. The plugs tell you if the engine is
getting too much fuel. See

http://www.sa750.com/plugs/plugs.htm

If the plugs look like the first case, then that verifies the engine is
getting the proper amount of fuel. If they look like the second case
then you know the fuel system has a problem and the tech's computer data
is wrong.

If the plugs look normal, then maybe a brake is dragging -- such as
caused by the stability control recall. 2005 models have a problem with
their stability control, causing engine power loss and a brake to drag.
Is yours a 2005 and has the recall been serviced?

I'd keep after the service manager. In this era of $3 gas, there's no
reason to accept 10 mpg. Good luck!

 

Thank you again, I will go to that website. As for a stability control
recall, I have not heard a word. One of the first things I did when I got
this car is registered online with Hyundai; I figured it was a way to get
word on such things quickly. But I have never had a message of any kind.
Mail, email, smoke signals or semaphore!

Judy Raskin

 

There are two recalls to reprogram the Stability Control (ESP) on 2005
Tucsons. The first is only for vehicles produced prior to 2/27/05 and
reduces system sensitivity. (Unofficially, I've heard that it could
activate at speeds of a few miles an hour, but I have no verification of
this.) The second applies to all 2005 Tucsons and makes the ESP more
active during "extreme driving conditions." It's possible the dealer
performed either or both recalls before you received the notice and you
weren't aware they did it. But I expect zero correlation with fuel
economy. In the first case, we're talking about infrequent erroneous
application at very low speeds, and in the second, we're talking about
conditions under which you're not likely to be driving the vehicle.

If you'd like to post your VIN, I'll run it and check for recalls.

 

I am willing to give you my VIN number, but not in this public forum. If
you will give me an email address, I will send it to you privately. Thank
you for checking this for me. -- Judy