Hi Guys,

Well as I have stated in other threads my car has been running really rich and it seems to be getting worse. I've decided lately to keep off the right foot to see if I can get it more economical.

now my TJ Ralliart's showing 18L/100km 2 tanks in a row now...
and you can smell how rich it is....

first noticed at a QMD Dyno day when the power output was lower than expected and a/f ratio was showing around 9-10 instead of high 12's like it should.

then I started to pay attention to my driving, what the power felt like, and how much fuel I was going through and I'm certain something is wrong.

the one thing that has me guessing, it doesnt blow smoke like I would expect it to..
however the inside of my zorst tip is alot blacker than usual.

Can anyone help me with where to start to look for a fault please.

Oxygen Sensor perhaps?

A more knowledgeable member will come along and explain how to test this soon enough :)

Jesus ........ how long is a piece of string.

Could be injectors, map sensor, TPS, fuel pressure regulator ...........

First thing would be to get the computy read to see if you have any error messages.

After that its gunna be a process of elemination.

Jesus ........ how long is a piece of string.

Could be injectors, map sensor, TPS, fuel pressure regulator ...........

First thing would be to get the computy read to see if you have any error messages.

After that its gunna be a process of elemination.

forgot to add, been done this week, didnt have any error codes but the auto lecky said that most sensors unless completely stuffed won't show an error,

any idea's how to check any of these??

also this might be related, occasionally (completely random except for its only when the car is warm) when I start the car sometimes it won't hold idle properly, seems to hover up and down between 500rpm - 1100rpm, if i leave it there it keeps doing it, if I drive off, next time i stop it idles fine. turn the car off, start again and it idles fine.
It's completely random except for the fact that it only seems to happen when I start the car warm.

the temp sensor can be a likely cause plus what old fart mentioned:D
good luck with finding the real cause. might take a bit to test it bit by bit till u find the cause. like old fart said it could be a few different things.

Oxygen Sensor perhaps?

A more knowledgeable member will come along and explain how to test this soon enough :)

When I had the oxygen sensor problem....i can smell unburnt fuel after a really hard drive plus with acceleration it feels like it's struggling. Anyway took it round to Mits dealer and they hooked it up to the diagnostic computer thingy and took the car for a drive and a graph of some sort (I forgot was it was now) was like the rollercoasters at dreamworld.
The fuel consumption was around 18-20L/100km but I didn't take notice of the idle rpm

Diagnostic codes will find the fault, or basic checks on each component.

It can't be the o2 sensor if it was rich on a power run. Closed loop fuel control turns off past about 70% throttle and 3500RPM on most motors.

Whats the specs on your car mate, any mods/work done to it at all?

Same as me I believe plus an FPR - extractors + exhaust + FPR.

My advice, take it to a mitsi dealer and get them to check it out.

Same as me I believe plus an FPR - extractors + exhaust + FPR.

correct, have had the FPR replaced with stock unit for a week with no benefit possibly even worse...

can anyone tell me how to test the sensors.. is it something I could do myself or have to take it to an auto leccy or mechanic???

The guy I work with has a 2000 WRX that had the same problem. He replaced the oxygen sensor and that fixed it.

.

why keep guessing, take it to a mech and get it diagged + fixed.

Thought I would do a bit of a thread mine.. rather than starting a whole new thread..

I have taken the Ralliart to a reputable Auto Electrician, and they hooked it up and said that it didn't come up with any errors.
They suggested the best thing to do would be to go through and individually check all the sensors, they could do this, however I needed my car back and the bill was already high enough for nothing really, they told me that if I disabled the sensor and didnt notice a difference when driving then that was the sensor that would be faulty and causing the ecu to run in limp mode so to speak...

Now on the weekend I unplugged the MAF and went for a drive, car drove a little sluggish but was still very drivable Just seemed to be running a little richer, could smell the fuel when I stopped..
then plugged the MAF back in and the car ran alot better than it was before I unplugged the MAF... can anybody tell me why this would happen?

You still have this problem and haven't replaced the O2 sensor? :nuts:

Can't answer your question sorry.

Thought I would do a bit of a thread mine.. rather than starting a whole new thread..

I have taken the Ralliart to a reputable Auto Electrician, and they hooked it up and said that it didn't come up with any errors.
They suggested the best thing to do would be to go through and individually check all the sensors, they could do this, however I needed my car back and the bill was already high enough for nothing really, they told me that if I disabled the sensor and didnt notice a difference when driving then that was the sensor that would be faulty and causing the ecu to run in limp mode so to speak...

Now on the weekend I unplugged the MAF and went for a drive, car drove a little sluggish but was still very drivable Just seemed to be running a little richer, could smell the fuel when I stopped..
then plugged the MAF back in and the car ran alot better than it was before I unplugged the MAF... can anybody tell me why this would happen?

if thats what happens when u unplug it then your maf (or afm) is working properly.

im having a problem with my car atm and hav found the air temp sensor and the knock sensor to be the problem. when cold the car sounds like V8 but goes nowhere.

the afm has i think 3 different sensors, a barometer, air temp sensor and mass air flow sensor. it COULD be any of these that is your problem however because your running so rich id say get a new oxygen sensor first.

if the problem still persists... see your doctor. :P

was gonna post but read somethin lol my bad

I had a very similar problem, ended up being the O2 sensor (even though the fault codes didn't pick it up).

Idle would some times be all over the place, stuttering on acceleration from rest and increased fuel consumption.

When the car is idling rough, disconnect the O2 sensor and see if the idle changes. Mine reverted to a smooth idle once disconnected, but immeadiatlly returned to a rough idle upon reconnecting the O2.

Jesus ........ how long is a piece of string

Tad longer than the one you cut last November.... :D

If O2 sensor cuts off at large TB opening or after ~3500 RPM - it could still be the fault. Cos most (reasonable) driving is done below those parameters. If u drive WOT and high revs - your gas consumption would be that high anyway.
The repair books tell in details how to check all these sensors. U need good digital V meter and few wires with thin ends to insert to those connectors. Takes cuppla hrs and few beers. More (beer) if u have an "assistant".

How is the AirFlowSensor connector at airbox? Dodgy?

Now on the weekend I unplugged the MAF and went for a drive, car drove a little sluggish but was still very drivable Just seemed to be running a little richer, could smell the fuel when I stopped..
then plugged the MAF back in and the car ran a lot better than it was before I unplugged the MAF... can anybody tell me why this would happen?
So once you plugged the MAF back in, the car seemed to be operating much better than it was before you unplugged it?
If so, then one possible problem was that there was a dodgy connection or the MAF wasn't plugged in correctly in the first place. Has you economy gotten better, or is it still pretty poor?

go get the car put on a gas bench and see when its running rich
it can realy only be.
coolant sensor
maf sensor

o2 sensor but i dont think so
leaking injector

have you got any fuel leaks? check under car on a hoist also check fuel cap
if the car has done over 100000km get the injectors removed and bench tested and cleaned.

Yeah, still havent looked at the o2 sensor at this stage, havent had much time for anything recently.

the Car is still running rich, and you can really smell it.. could a dead CATT cause this sorta thing at all??
their is no leaks or anything that we can see..

after connecting the MAF up again it was like the sensor had been reset... and today its running about the same as it was previously.
I think I will replace the o2 sensor soon can't be a bad thing...

thanks for your help guys.

Yeah, still havent looked at the o2 sensor at this stage, havent had much time for anything recently.

the Car is still running rich, and you can really smell it.. could a dead CATT cause this sorta thing at all??
their is no leaks or anything that we can see..

after connecting the MAF up again it was like the sensor had been reset... and today its running about the same as it was previously.
I think I will replace the o2 sensor soon can't be a bad thing...

thanks for your help guys.

would smell like rotten eggs. get a stick and tap it, see if u cant hear things rattling inside

the cat wount cause high fuel usage unlesss its totaly blocked

the o2 sensor will throw a code if its not working

you have got other problems,
try find a mechanic with a gas bench and a carmin scaner that knows how to use it. they will tell you straight up whats wrong with it.

Often a car will run very rich if the collant temperature sensor fails.The amount of these things that pack up and the computer doesn't throw a code or light is amazing.Likely its gone open circuit and the car is running in cold start mode all the time.Get a multi meter and test it for open circuit.That means its not passing any electric current and needs repalcing.If it isn't replaced it will kill off the cat and the o2 sensor 'cause they don't like overly rich mixtures and it will start getting costly.The mitsi dealer should have picked the problem 'cause the diagnostic computer tells the mechanic the ranges at which the sensors run.What I mean is on cold start the coolant temp may be 10 degrees and you can see this temp on the screen on the computer.If the temp doesn't go up as the car warms up,ie it stays at 10 degrees,the ecu will think the engine is still cold and deliver to much fuel.
Keep us posted on how you go.

the cat wount cause high fuel usage unlesss its totaly blocked

the o2 sensor will throw a code if its not working
Forgive me if I'm wrong, but from what I've read on these forums with people who have high fuel usage, it's turned out to be the O2 sensor 99% of the time and I remember them saying it never reported any faults during diagnostic testing.

Forgive me if I'm wrong, but from what I've read on these forums with people who have high fuel usage, it's turned out to be the O2 sensor 99% of the time and I remember them saying it never reported any faults during diagnostic testing.

Thats right. I'm one of those 99%. The O2 can malfunction but still return a voltage, so the ECU thinks it's all good. Two diagnostic tests came up fine, even the first of two multimeter tests past, when I got it tested.

To the OP, just unplug the O2 completelly and see how the car runs. It will still waste more fuel, but should run allot smoother. If there is any change, then it's most likelly the O2.

It's easy to get to and unplug (I have posted pics of how to do it in THIS (http://www.aussiemagna.com/forums/showthread.php?t=35438&page=2&highlight=sensor) thread).

Forgive me if I'm wrong, but from what I've read on these forums with people who have high fuel usage, it's turned out to be the O2 sensor 99% of the time and I remember them saying it never reported any faults during diagnostic testing.

if you get someone to test it properly not just look for a code or a voltage
you need to look at a wave form siginal.
creating a vacume leak should throw the siginal to lean
and clamping the fuel return hose would make it rich

o2 sensors can still be working but give a slow responce
a gas bench might show that its rich only at idle or only at 3000rpm or only when theres a cat sitting at your front door.

i just dont understand why you would just start replacing things if theres no sign of a fault
its a costly way of doing it.

o2 sensors don't really give slow response. Usually the problem is either the heating element in them fails (if it's a heated sensor), or they get contaminated from rich mixtures. When they get contaminated, the sensor constantly thinks it is running lean, resulting in the ecu just dumping more and more fuel into the engine.

Another way to check it is to put a digital multimeter across the sensor connections while the car is at operating temperature, and keep an eye on the voltages. At idle it will oscillate between 1v and 0.3v typically, and when you rev the car, you should see significant difference from the values you were seeing at idle, and it will sit roughly steady. If there is almost no difference whether idling or revving, the o2 sensor needs replacement.