Hello all,

Firstly, my apologies for another fuel economy question.

I have recently purchased a 2002 TJ Advance wagon with 100,000Ks on the clock.
The plugs and timing belt are all done and the car purs along nicely.

Question, the car is only used for stop start city driving, which I understand uses heaps of juice, but its ticking over at 19.5L/100KM.

I have had it checked over by the magna service centre in Geelong and they tell me that there are no codes and its running fine.

Any thoughts, surely the car is using way too much juice.

What do I do??

-Replace the fuel filter (this is good even if it's not the problem).
-Check the O2 (oxygen) Sensor using multimeter (maybe at an autoelec) as they will not cuase a fualt code to log, or simply replace. If the O2 sensor is stuffed it will prohibit the car going into closed loop mode (among other problems). In closed the loop mode the car adjusts the air/fuel ratio to increase the fuel economy of the car at light throttle loads.

Thanks Mate,

Will give that a go.

I have read on other posts that the O2 sensor will come up code if its stuffed... Anyway, its no harm in throwing another one in as the car is costing me a fortune to run.

Life cycle of an O2 sensor varies but 100,000km is a good time to change them along with timing belt, plugs etc...
I recently changed an O2 sensor on a KH Verada. The driver was averaging 17l/100km in stop start traffic.
After changing the O2 sensor and resetting ECU the first tankful she averaged 13.3l/100km, second tank down to 12.6l/100km and shes wrapt.
Trip is the same ie work and back and drives it similarly with the occassional hard acceleration.
Definately worth changing.

And what does an O2 sensor cost roughly?

Thanks Mate,

Will give that a go.

I have read on other posts that the O2 sensor will come up code if its stuffed... Anyway, its no harm in throwing another one in as the car is costing me a fortune to run.

I should have said it doesn't always log a fault. I know it didn't with mine and a few other guys. It depends on how the sensor fails.


And what does an O2 sensor cost roughly?

I've heard prices as low as $66, but on average about $100.

You can get generic ones where you have to solder on the plug or ones with the correct plug already fitted.
I think the correct NTK ones with the plug already fitted, grommet, etc.. are about $100. These are available at most auto places, same as spark plugs.

I should have said it doesn't always log a fault. I know it didn't with mine and a few other guys. It depends on how the sensor fails.



I've heard prices as low as $66, but on average about $100.

For a Magna Specific NTK brand $140.
For a Generic NTK that you cut and solder your plug onto around $90 is about right.

Um, don't just change things if they are not faulty.

Check the ECU codes, it will tell you if there is an o2 sensor problem, and then remove it and take it to a EFI shop where they can do a 2 minute check.

Your fuel filter will also be fine, it could not possibly cause high fuel consumption.

Your best bet is to check fault codes, they will tell you what is playing up.

Fair call Turbo charade.

The problem is the ECU came up with no codes and the car is still running at 19L/100K.
I have to try something...

whats it get on the open road???? i get 15L/100 city, and up to 20L/100 sometimes, but put it on the open road and im getting under 10L/100.... there may not be a problem at all, if you are doing short stop start driving at speeds under 80 you will see a high consumption rate, take it on the fwy and see what she gets there

Another Geelong person? Poor you! Well, i know someone who had issues with their oxy sensor and it didnt log a code. But it did run pretty average. Could it be the coolant temp sensor? If that is bung it might think that its on warm up all the time...

The ECU wont necessarily give you a fault code if the oxy sensor is stuffed.
It may still work and pass the multimeter test but be so filled up with soot that the reading it gives to the ecu is incorrect.
If you've checked everything else ie: air filter, plugs and theres no fault codes, this is the number one suspect.
Call Petroject on 9720 5411 and see what price they can do for you

How are you determining that the fuel econ is bad? If its via the trip computer, then take fuel logs and physically calculate it yourself.

Can I suggest you try again, after having the battery disconnected for 30 seconds or so.

If you dont get a fault code from that I would probably start by unplugging the sensor and driving like that for a week. What that will do is revert back to the ECU's fuel map, instead of running closed loop. The ECU's fuel map is fairly spot on, so if your fuel econemy comes back good, then you have PROVEN to yourself that its the o2 sensor.

o2 sensors rarely fail.

Better yet, try a mates sensor which you know works.

Poor wheel alignment?

My TJ uses a little more fuel when the wheel alignment heads out.

Stop start to work I get 14L/100Km tops.

I am lowered on 17's with extractors and oversized throttle body.

Be sure to change your air filter if it's been a while also.

19L per 100 is a bit 2much

i work in the city and drive from rowville to the city almost everyday and in peak hour traffic im getting between 12-13L per 100 and normall driving on open road i get down to 8L per 100.

maybe reset your ECU and go for a drive not flooring it and it should bring your fuel consumption down (i think) but thats what i usually do and it works for me

i did a full tank of fuel the other day for 520km. my old verada used to get heaps more than that. maybe i might do the o2 sensor at my 100 000k service in a few months??? does it really make it that much more fuel efficient? my car idles a little rough too. is that standard of the verada's? my old one was over 3 years ago and i cant really remember what it was like.

how on earth did u get it to run 19L/100km? i can't even get 14L/100km even if i tried...and i dun take off slowly either...

o2 sensors rarely fail.


Magnas must be the exception, I know of a few that needed new sensors (due to overly rich factory tune?)

I jsut got a quote for trade price (From Mits service centre) for o2 sensor. $310.... I think I will go to repco and try one of those aftermarket ones.

I did unplug the battery for an hour and then drove the car nice and slow, but the problem still persists.

I will report back after I've fitted the sensor.

I jsut got a quote for trade price (From Mits service centre) for o2 sensor. $310.... I think I will go to repco and try one of those aftermarket ones.

I did unplug the battery for an hour and then drove the car nice and slow, but the problem still persists.

I will report back after I've fitted the sensor.

Maybe better to try what TC said earlier before buying the o2 sensor.

Unplug it and drive around like that for a few days. If there is no change in the economy it's most likely the sensor. There are a couple threads here showing the sensor plug (that you need to disconnect) location. I posted a series of pictures in one of the threads showing how to get to it.

The only 2 sensors that don't throw codes on a 3rd gen are the O2 sensor and TPS.

Cheers
Heath Young

My girlfriends brother had the same thing happen to him. It was the Oxygen sensor.

Edit: He has a TL.

Is there a specific place in victoria that sell O2 sensors for the 3rd Gen and is it hard to replace yourself? What about a mitsu dealer, do they still sell 3rd gen stuff?

cheers

Is there a specific place in victoria that sell O2 sensors for the 3rd Gen and is it hard to replace yourself? What about a mitsu dealer, do they still sell 3rd gen stuff?

cheers
Mitsubishi dealer should sell them. Maybe try the parts dept.

Mitsubishi dealer should sell them. Maybe try the parts dept.

Bursons, Repco, R&E Auto etc...... Any auto parts store will sell a specific O2 model for our 3rd Gen. Get NTK brand - It is the OEM replacement about $140 is normal price for a 3rd Gen Magna NTK.

If the sensor has siezed in the socket (more than likely) It's a prick to get it out.

hey guys my fuel economy stated to creap up to 14.2 in the city going to work blacktown-parramatta ive since chaged only my from spark plugs with uridium type and my economy went down to 12 yet to do the rear bank yet. ive spoken to a few techs they claim that it common for moisture to get into the plugs causing them to get a rusty look and stat to foul up, ur cruise idle will start go go over 3000rpm when that happens

hey guys my fuel economy stated to creap up to 14.2 in the city going to work blacktown-parramatta ive since chaged only my from spark plugs with uridium type and my economy went down to 12 yet to do the rear bank yet. ive spoken to a few techs they claim that it common for moisture to get into the plugs causing them to get a rusty look and stat to foul up, ur cruise idle will start go go over 3000rpm when that happens

Its uninformed, guesswork posts like this which make people buy iridium spark plugs.

They can not increase fuel economy if your pre-existing plugs are already in good condition. Knight rider, you would have found changing plugs to ANY new ones would have increase fuel econ because yours were simply too old.

ok guys. got the 100 000 service done and now i'm getting about 320kms to a full tank of stop go driving around the city. this is with air con barely on most of the time and driving to keep up with traffic so not really that hard. i am going to do a few more tanks but i think something is really wrong with my car. it's going in tyres & more at strathpine next thursday for a health check and they are gonna check codes and run it to check that everything is running smoothly.

i mentioned that there has been a fair bit of concern about the 02 sensors on here and he said that after the service it's possibly be the only thing but he's still uncertain.

wanna throw those guys a free plug too. there was a hiccup with the service and they were more than happy to swing the money back to me for a power steering belt and labour from another mechanics (cause i couldn't get it to them to repair) and i was treated very fairly and they were very appologetic about the mix up. i can assure you their work is excellent and the service is just as good.

put 38psi in the tyres dont use the air con dont be a lead foot

take any crap out of the car that dont need to be in it
no roof racks

make sure none of your brakes are sticking

like tc said if there is no codes the problem is else where
if unsure take it to mitsu they can check it with the mut o2 gives a live reading

at 100000km i would be getting the injectors cleaned a carbon blast and a throttle body clean

make sure the air filter is clean and it has the right plugs in it.

use a thiner grade of engine oil

I don't want to steal the thread here, but my usage is at 17.3L/100 its usually around 12 and as low as 10.7 sometimes. It jumped to 17 after I reset the in-car readout by pressing all 3 buttons while driving. Would this be the cause?

38 PSI!!!! i dont even run that in my ute with a load in the back!!!! justb had service done so all plugs and the rest should be fine. it's a problem that continues to get worse so it's a little bit of a waiting game to see what's going on. i justfilled up then and without a fancy trip computer i'll just have to wait and see. i know that i went to the valley and back from west end yesterday in brisbane and it cost me 1/8 of a tank. that's a return trip city driving of about 16kms. that is pretty ****.

38 PSI!!!! i dont even run that in my ute with a load in the back!!!! justb had service done so all plugs and the rest should be fine. it's a problem that continues to get worse so it's a little bit of a waiting game to see what's going on. i justfilled up then and without a fancy trip computer i'll just have to wait and see. i know that i went to the valley and back from west end yesterday in brisbane and it cost me 1/8 of a tank. that's a return trip city driving of about 16kms. that is pretty ****.

Yeah there was another post not long ago about the correct tyre pressure, 38 PSI was what was recommended. I would have thought that'd cause uneven wear on the tyre and a rough as guts ride. Don't really think its worth the slightly less resistance to save fuel when the car will sustain more wear from the roughness (like shocks and the car body itself).

Not only to mention, 38 PSI when cold in the middle of summer would be excessive on a 44C day when driving longer distances, probably increase chance of blowing a tyre. On a wet road you'd have a much greater chance of aquaplaning which is dangerous.

Man, the difference between even 30PSI and 38PSI is not going to make a huge difference to the fuel economy, especially the difference you have!

Hmmm, try a different fuel, say Shell as opposed to BP or Caltex opposed to Mobil etc. Not all cars respond the same!

You may have a blocked exhaust system, a collapsed muffler or cat as well (shouldn't but hey). Does the exhaust sound correct?

I don't think the engine codes show a faulty coolant temperature sensor? If that is faulty wouldn't the car always run on startup richness?

Is the car changing gears at the right times? If not you may need to get the auto serviced. Its probably holding in a shorter (that is lower) gear too long as a possibility.

My parents have a TF magna and the only thing they've had to do with it is replace the tyres and normal servicing. Its gone 230,000km without the cleaning, without replacing the O2 sensor etc etc etc and they're still getting very good fuel economy out of it. About 8L on the highway and 12 to 13 in the city.

The O2 sensor shouldn't need replacing at all, unless its been contaminated with something. silicone is one of the major culprits of contamination and unless the silicone is removed it will keep on contaminating it. Thats why you should use gaskets as opposed to silicon! (the thermostate housing is probably the only exception)!.

Maybe if you're unlucky the O2 sensor will go faulty, but 100,000km is not a general rule like it is with some other parts! (i'm not saying they don't go faulty, but yeah)!

Anyways, hope you get the problem sorted! :)

Not wanting to OT this thread any further, just want to quickly point out running higher then recommended (ie. plycard figures) tyre pressures is a lot safer then running under-inflated tyres. The figures on the plycard tend to be the minimum safe pressure whilst keeping the ride comfortable.

Increasing tyre pressures will decrease the ride comfort, but will benefit in fuel economy, tyre life, control and braking performances.

You would actually get an increase in tyre wear if the tyres are underinflated because what happens is the tyre will become 'W' shape (looking at the tyre cross-sectionally) rather then a nice 'U' shape.

Heres my experience as a Courier.

I was getting well over 400kms around town. I don't drive like an old lady(probably not very lady like at all...), I drive as quickly as I can within safety and reason.

I could get 800 kms on a country trip.

On LPG I lose about 100km's a tank around town.

Maybe yours has the V8 option?

hahaha. i wish it had a V8 option. i had a new exhaust from cat back put on about 2 months ago. had a major service done with new seals and idler pulleys timing belt air filter oil and tune. everything is running as it should bar the bit that's sucking fuel!!! big highway run today. will see what's crackin there.

You should throw money away replacing parts systematically insteady of just diagnosing the problem and replacing what is needed.

cars come from the factory with 45to 50 psi to stop flat spots in the tyres
and they dont blow up on a hot day

running 38psi in the front is fine as all the weight of the gbox and engine is on top of them
run 36 in the rear

if the middle of the tyre starts to wear let them down to 36f and 34r

i just picked up a tj advance sedan with 200,000 ks and will be giving is a big test over the hols around 2000 ks about 1200 of that will be highway crusing so ill give it a test on gas 1 way and petrol the other and let you guys know how she goes

I run 40 all round and they dont wear unevenly in the middle and there's nothing wrong with the ride.

I'd suggest checking the fuel rail pressure for the high consumption problem.Fuel pressure regulator/vac line might be producing wrong pressure. Wrong pressure=wrong injector flow and a leaky vac line=high fuel rail pressure.

I sitll reckon around 34PSI would be ideal. The few cents saved by better mileage may in the end help cover the cost of the shocks etc wearing out quicker!

You don't have a hole in the tank?

You should throw money away replacing parts systematically insteady of just diagnosing the problem and replacing what is needed.


not everyone is a mad mechanic like yourself mate. i dont know a great deal about the 3.5L yet. i am trying to find a problem and i havent replaced anything as yet until i have had it checked at the mechanics for every possible thing that might be wrong with it in relation to excess fuel consumption. i dont have the money to waste that's for sure.

cheers to everyone throwing me the ideas. i upped the tyre pressure to 36 all round. i had really uneven pressure FL 33 FR 37 RL 30 RR 36 and that was after having it all "checked" the other day at some shonky tyre place when i got a puncture repaired.

Just a small note on the air pressure in tyres debate ...

I have, and will continue to run 38-40psi in my tyres.

I am now looking to replace my tyres after 60,000km's. I obtain regular wheel alignments and balances just to make sure everything is A'ok. My tyres have worn evenly.

I have a magna Altera 97 model TE, Automatic, Driving on grandma mode most of the time and petrol consumption is less than 350 kms for the full tank, one more thing as well , the car heat up to the middle quite quick ( liek in less than 10 minutes)

other symptoms

when accelerating , it's automatic but when changin from first to second it takes quite a while liek 2 seconds for the second gear to kick in,

if I need to get my o2 sesor check, where is teh best place recommended (cheap and tidy) in arround north shore chatswood NSW, even arround sydney will be ok too.

how much will it cost wodl be great.:D

I have a magna Altera 97 model TE, Automatic, Driving on grandma mode most of the time and petrol consumption is less than 350 kms for the full tank, one more thing as well , the car heat up to the middle quite quick ( liek in less than 10 minutes)
3rd gens warmup to operating temperature pretty quick, less than 2m is 'normal' imho.
Usually no longer than the 3rd set of lights out from my garage.

And they stay warm too... restart mine within 3-4 hrs and the temp needle is
back up to middle in no time at all, like before its even out of the garage.


when accelerating , it's automatic but when changin from first to second it takes quite a while liek 2 seconds for the second gear to kick in,

your auto might be due for a service, adjustment and/or powerflush

could try resetting the ECU by disconnecting it for 10mins & retraining

Thats good.. ive been getting 20-21L/100kms the last few tanks..:P

413km was a record out of a tank for me since engine is done..:)

Just a small note on the air pressure in tyres debate ...

I have, and will continue to run 38-40psi in my tyres.

I am now looking to replace my tyres after 60,000km's. I obtain regular wheel alignments and balances just to make sure everything is A'ok. My tyres have worn evenly.

Many opinions about this.

I have been in the industry for some time, and have heard all the opinions, and experts etc etc. I've also dealt with many of the tyre manufacturer's engineers. They say even a 2psi increase or decrease can alter the way a vehicle behaves on the road.

From what I have learnt the best way to go is:

As a rule of thumb they say to add 2 to 8 psi onto whatever the manufacturer states on their tyre placard. (depending on which manufacturer though, some are better at being accurate with their tyre placards then others:)

Dont go above 38psi as a maximum on the road!!) Manufacturers quote slightly lower tyre levels to give a nice soft initial ride for people test driving their cars, and are prepared to lose some handling, and not worry about tyre wear! When you actually own the car, and want the best combo of comfort and performance going that 2 to 8psi more will give better fuel economy, tyre wear, and improve handling, without working the rest of the cars suspension any harder, or ruining ride quality.

I find 36psi is best on my TJ Magna. Originally I would occassionally swap and change up to 38psi to see if it was worth it. Always found myself back at 36 though as it just felt right:)
After running at 36 psi for some years now, I am getting around 50-60,0000kms from a set of tyres, and no problems with shocks/suspension etc. Car has now done 150,000 and all good. Still nice and tight and smooth as well with no rattles.

(on another note highly recommend using 98 octane fuels eg BP ulitmate or Shell V. All I ever use now. Tried a few tanks of standard unleaded early on, but really noticed the difference. Now car's economy is the same as when I bought it, and engine just as smooth. Even has the original platinum plugs it left the factory with, though will change shortly so I don't tempt fate.!! Mechanic always comments how clean fuel filter is, and how smooth engine is, and how well it runs. Worth spending on these fuels if you are going to keep the car longterm. Not that much difference in price when you factor in the extra km's from a tank!)

Now they say for track days (constant high speed, nice smooth track) 40 to 44psi is the way to go. But just remember to let them down a little when its all over.
Running pressures 40psi and over whilst on the track is fine, but on the road you are asking for trouble. Sure the tyres may wear and handle ok, (though alot of the time they will wear unevenly in the middle, as an under inflated tyre wears on its edges) but you are adding extra stress to your wheels, suspension, and the cars whole body, when driving on average Australian roads (read not super smooth like a track....potholes..joins..driveways, etc etc)

End result of these sort of pressures on the road with time is worn suspension, rattles, and loosing of the body and damage to components, more chance of bending rims. Not to mention if you already have harder lower sports suspension installed to begin with!!!
Also pressures of 40psi and above generally offer lower wet weather performance on the road.
In wet driving some give in the tyre is beneficial to performance on our rough, potholed roads.

One tyre engineer once told me...." It's all a compromise with tyres, trying to find that inbetween that gives the best overall result. Same with their pressures...can't go too high...can't go to low."

Just from what I'v picked up and learned over the years.....goodluck