Daniel B. Martin

Miles per tank is not an accurate measure of fuel consumption. Miles per gallon is.

Please disclose your fuel usage in miles per gallon and perhaps there will be some useful information in the feedback.

Posts which solicit technical information should include ...
- model year
- transmission type
- odometer reading
- repair history
... etc.

More detail is always helpful.

jargoone

It's not that hard to figure out, you know. It might take you 30 extra seconds. Don't come asking for help if you're too lazy to give more information.

chris j vurnis

Hello Slammed:

Your first problem is that you use 89 octane gas. Owners manual
recommends 91. It will slow down your car and reduce mileage.

Do you use a lot of fuel additives... they can build up and make things worse in your engine.

Vyrus

iTrader: (4)

Really? Can you (or anyone else) explain because I sometimes use the N.O.S. Octaine Boosters, and I was not under the impression that they could, even over a given period of time, harm you engine.
Thanks,
Cyrus

Daniel B. Martin

Your car is using too much fuel. These possibilities exist:
- you are burning it
- you are leaking it
- someone is stealing it
- you are using gasohol


Burning it...
- fuel injectors are sticking open
- "tired" Oxygen Sensors
- bad fuel pressure regulator
- obstructed fuel return line
- clogged air cleaner filter
- bad Engine Coolant Temperature Sensor
- stuck-open thermostat (engine never goes into closed-loop mode)
- transmission defect (never shifts into fourth gear)
- dragging brakes


Leaking it...
Search for fuel leaks by sight and odor. However, some fuel leaks are so
tiny that they escape the human senses. One way to find them is to have
your mechanic use his exhaust gas analyzer. Switch the tester to HC
(hydrocarbons) and then pass the probe along the entire fuel system,
starting at the fuel tank, forward along the fuel lines, past the filter,
all around the engine, then along the return line and back to the tank.
The tester is far more sensitive than the human eye or nose. When the
probe passes near a tiny leak the reading will abruptly increase.


Stealing it...
Perhaps someone is stealing small quantities of fuel, not for its financial
value but as a prank. Install a locking fuel filler cap.


Gasohol...
- You may have been buying gasohol rather than gasoline, without realizing it.
- You may live in one of those regions which is required to sell oxygenated
fuel.

Now that MTBE is in disfavor, gasohol is the most common oxygenated fuel.
Alcohol has a lower energy density than gasoline.

Tai Mai Shu

I belive this to....91+ always, don;t you want your maxima to be happy?

Yur Shu Un Thai

Hey, I use 91 octane also.

Tai Mai Shu

is this some sort of off shoot of my name?

Yur Shu Un Thai

Not that I am aware of

SunMax

iTrader: (2)

I can smell gasoline (from the exhaust) everytime I start the car after the car had been park for a while (i.e. engine is cold). What kind of tests I should do to fix the problem?

emax02

iTrader: (1)

The smell you are descriping is most likely "Carbon" , this meens one of 2 things, either your catalitic convertor{s} are not working properly or your car is running to rich{probably the later}

If you want to check your main cat. you can slide under your car and physically bang your cat. If you hear stuff rattel around inside, this whould meen your cat. is shot. The affects of a bad cat can be , bad smell, and drasticaly reduced gas mileage if it is cloged. If you here stuff rattle around inside the cat it is most likely cloged up and this meens your exaust system is not breathing properly. This whould give you bad performance, a foul smell and poor fuel econamy.

Other things you should check are:
Your MAFS and your engine collant sensor, you can test these two by buying a repair manual and using a inexpensive volt meter.

Let us know how it turns out. BTW other things may be at folt{o2 sensors etc.} but the stuff I listed is what best meets the decription of your problems in my eyes.

Good luck.

Daniel B. Martin

Perhaps your engine has one or more fuel injectors which stick open. When you turn off the engine the residual pressure in the fuel rail "pees" into the intake manifold. Next time the engine is started it gets a gulp of raw gas and sends some of it right out the tail pipe. The Catalytic Converter doesn't work until it is good and hot, so it didn't prevent this.

This hypothesis can be tested by making a fuel pressure test.

Daniel B. Martin

A fuel pressure test is a standard diagnostic test. You will find instructions and a diagram or picture in the Chilton repair manual (page 5-3) and the Haynes repair manual (page 4-3,4).

Bleed the fuel rail pressure by pulling the fuel pump fuse (#32, 15 amps) and making several attempts to start the engine (it won't start). Install a T-fitting with a pressure gauge in the flexible rubber fuel line just downstream of the fuel filter. Install the fuel pump fuse. Start the engine. With the engine idling you should see the pressure maintain a stable 34 psi. Temporarily remove the vacuum signal hose from the fuel pressure regulator. The fuel pressure should increase to 43 psi. Reconnect the vacuum signal hose and operate the throttle to vary the engine speed between idle and 3000 rpm. The fuel pressure should vary between 34 and 43 psi.

Readings less than 34 psi could be caused by an obstructed fuel filter, a weak fuel pump, or a bad fuel pressure regulator. Readings greater than 43 psi could be caused by a bad fuel pressure regulator or an obstructed fuel return line.

After turning the engine off the fuel system should hold pressure for many hours. If the residual pressure bleeds off in only one hour that is a sign of a problem... bad fuel pump check valve, injectors with an internal leak, bad fuel pressure regulator, or an external fuel leak.

NYCe MaXiMa

iTrader: (9)

Interesting.
I get the same "smell" as I start the car and I noticed something funny. I see the fuel needle on the gauge literally drop just a little bit as the car reaches operating temp and I'm driving it. My fuel consumption is "fair" i'd guess, although it can be higher as I recently calculated 21.7 mpg on 60% highway driving. My car has 58k miles on it, I don't think the Catalytic converter can fail so quick, can it? I do need 60k mile service done though.
I will do the diagnostic as I'm familiar with it from my previous battles with this problem on my other car.