Whats wrong with AU? Out of Fuel? Electrics?

[Gypzy]

Gidday, been trawling thru these pages for an answer, can't find it! My well maintained, high klm 4.0ltr "seems" as though it's starving of fuel. replaced all the obvious components but to no avail, (fuel pump & filter, pressure regulator, injector service, even crank angle sensor & coil pack...). has become an expensive problem that i can't afford to go much further on. Can anyone point me in the right direction, thanks.

[Maka]

Replaced your knock sensor or o2 sensor lately? A ecu scan can pinpoint faulty sensors & running issues also. Good luck!

cheers, Maka

[Sox]

Need more detail.

High revs, low revs, under load, light load, part throttle, full throttle, cold, warm, consistent, intermittent, etc...

[Gypzy]

No, havent replaced knock or 02 sensors ever. Originally it was hard to start but only in mornings, crank over but not firing up, allways easy start in arvo. At 2000rpm, 40kmh in second gear (thru roadworks, light throttle) it, only on occasion has the feeling of running out of fuel, sometimes stalling. Feels sluggish when accellerating in 4th at 80klm. Other times it runs just fine.

[Bushbasher]

check the little mesh filter at the start of the fuel rail.

[Sox]

Originally Posted by Gypzy

No, havent replaced knock or 02 sensors ever. Originally it was hard to start but only in mornings, crank over but not firing up, allways easy start in arvo. At 2000rpm, 40kmh in second gear (thru roadworks, light throttle) it, only on occasion has the feeling of running out of fuel, sometimes stalling. Feels sluggish when accellerating in 4th at 80klm. Other times it runs just fine.

With the bit in bold, do you mean it runs fine at all other operating conditions other than you've described, or it runs fine sometimes even under those conditions?

You also mentioned high k's. How high?

When were the high tension leads replaced?

[Gypzy]

Yes you could say it is an intermittent issue. It would run ok at said speeds on other occasions. 2000rpm seems to be a common dinominator. My 99 AU XLS ute has done 360000ks. I've had it from 10000k with only general maintenance issues, allways had good highway klms and regular sevicing.

[Gypzy]

And yes i've done plugs, leads, and engine diagnsis, machanics are scratching their heads!

[Sox]

Originally Posted by Gypzy

Yes you could say it is an intermittent issue. It would run ok at said speeds on other occasions. 2000rpm seems to be a common dinominator. My 99 AU XLS ute has done 360000ks. I've had it from 10000k with only general maintenance issues, allways had good highway klms and regular sevicing.

These kind of intermittent faults can be hard to find.

Do you know when the high tension leads were last replaced?

[Sox]

Originally Posted by Gypzy

And yes i've done plugs, leads, and engine diagnsis, machanics are scratching their heads!

Ok.

How long has it been doing it for, and is it getting worse?

[Gypzy]

This problem started about six months ago, in and out of the machanics ever since, the last bloke i took it to is an Auto electrician/machanic, who even put a 2nd hand ecu in it. same problem exists. Not getting better or worse, same. Leads were replaced in 3 months ago. Easier to start since new coil pack and MAP sensor replaced 2 weeks ago.

[Sox]

Originally Posted by Gypzy

This problem started about six months ago, in and out of the machanics ever since, the last bloke i took it to is an Auto electrician/machanic, who even put a 2nd hand ecu in it. same problem exists. Not getting better or worse, same. Leads were replaced in 3 months ago. Easier to start since new coil pack and MAP sensor replaced 2 weeks ago.

Sounds like a very tough one if mechanics and auto sparky have seen it.

I'll keep thinking about this, meanwhile maybe some others will chime in.

[mik]

How old old is your catalytic convertor? Might not be the problem, might be part of it though?

[Gypzy]

Cat converter never been replaced.
Turning into a money pitt as i'm not doing the work on it.
Thanks all and stay tuned. Auto sparky will be seeing me again when he gets back from holidays on 13th January. Sucks when we're clutching at straws hey!
Any more suggestions, bring em on, Ta.
Gypz.

[aussiblue]

This could very likely be a camshaft position sensor (CMP) (as distinct from the adjacent crank position sensor - CKP) failing. Check for fault codes; you'll get a saved P0340 code if the CMP is failing. It's not foolproof with an intermittent but also disconnect the wiring harness from it and see if you get the correct 800 to 900 ohms across the sensor terminals.

[Maka]

Gypsy, whats your fuel economy like & its not pinging at all is it?

cheers, Maka

[Gypzy]

Guys fuel economy is unchanged at around 700ks on a full tank (82ltr) Mostly highway use.
PO340 did not come up during diagnostic.

[GASXD]

Gypzy, as Maka said, throw in another o2 sensor... My AU had similar issues (faulty o2 failed to show up on scan) and after we replaced the o2, with one from a BA motor, she's been right ever since.

[Gypzy]

OK, give it a go but as no codes come up with an "02 sensor" reading, we could be still clutching at straws!? Hope it's a cheaper option at this stage. Cheers.

[Evgeni]

Originally Posted by Gypzy

OK, give it a go but as no codes come up with an "02 sensor" reading, we could be still clutching at straws!? Hope it's a cheaper option at this stage. Cheers.

The cheaper option would be to use a multimeter to diagnose the o2 sensor, as opposed to just throwing one in. $10 multimeter, some pins and jumper wire would be around $20. We can walk you through if you need help.
A possible scenario is a vac leak causing a lean condition. The computer will respond by running a rich mix to counter the condition. A rich mix is good for start up and when you get close to WOT, but would also lead to a lack of power at cruise etc.
Just a theory, but you need to look at what is actually going on, otherwise you are just throwing parts at it.

[Gypzy]

Thanks evgeni, yeh i'm over just throwing parts at it, bit different to a XY 250 motor! At least with the old motors you could work it out and fix yourself.
What i'm doing is just gathering your and everyones comments to go back to auto sparky later on. i don't even know were to find this 02 sensor! This problem seems to have stumped alot of people, cheers.

[Bushbasher]

O2 sensor is screwed into the exhaust manifold.

[Evgeni]

I guess the easiest diagnosis here then, is to simply reach down and unplug the o2 sensor. As Bushbasher said, it is on the exhaust manifold - just follow the four wire connector up, squeeze the tab on the harness and unplug the sensor from the loom.

The purpose of the o2 is to give the computer a reading of the oxygen content in the exhaust via a voltage reading. It will then adjust the fuel mix at idle and cruise to achieve 14.7:1. When you unplug the sensor, the computer will or should revert to a default of 450mv which equates to 14.7:1.

If your sensor is faulty, you should notice an improvement at cruise once the thing has been unplugged, which would give you some confidence that replacing the o2 would help solve this problem. It is not a sure fire diagnosis, but in the interest of time and cost saving, it can help point you in the right direction.

I picked up a bosch one from ebay a little over a year ago for $40, so not a major expense.

[Gypzy]

That sounds like an easy enough exercise, i'll have a go at that.
The engine diagnosis included connecting engine to "smoke machine" to check for vacuum leaks. Could not detect any vacuum leaks.

[Gypzy]

Disconnected 02 sensor, taken for drive, no different. Still got that starving for fuel feel, mostly at light throttle. Put foot down and she takes off goodly.

[Sox]

Originally Posted by Gypzy

Disconnected 02 sensor, taken for drive, no different. Still got that starving for fuel feel, mostly at light throttle. Put foot down and she takes off goodly.

Sounds like you've found the problem.

[Gypzy]

Originally Posted by Sox

Sounds like you've found the problem.

So your suggesting that weather the 02 sensor is connected or not, and it performs in the same way, that this could be the issue? At around 40 bucks, and she's done 360000ks, wouldn't hurt to shout her a new one anyway. i'll give it a go, Ta.

[Sox]

Originally Posted by Gypzy

So your suggesting that weather the 02 sensor is connected or not, and it performs in the same way, that this could be the issue? At around 40 bucks, and she's done 360000ks, wouldn't hurt to shout her a new one anyway. i'll give it a go, Ta.

Logically, the car should perform different with the sensor disconnected (why have it if it doesn't?).
The fact it doesn't, points towards it being stuffed.

[Gypzy]

Originally Posted by Sox

Logically, the car should perform different with the sensor disconnected (why have it if it doesn't?).
The fact it doesn't, points towards it being stuffed.

True that. Be a week or two till we find out though. Watch this space!.

[Evgeni]

It does suggest that the sensor is not contributing, but you can't conclude anything without knowing what the computer defaults to once the sensor is unplugged. At that odo reading, likely the sensor is stuffed, but the smoking gun would be to backprobe that o2 and get a reading from it.
Make sure the o2 heater circuit fuses are intact - from memory, they are located in the engine fuse box.

Guess we will know soon if you are replacing it anyway.
Good luck, let us know how it all goes.