Air/fuel Gauge

[tdan]

Hi all... I have an Autometer A/F gauge fitted to my car. It is connected to the exhaust via an Autometer A/F probe, so it is not coming off the factory sensor or the ECU. The problem I am having is that after driving the car for about 30 minutes (30 minutes constant driving) the A/F gauge displays no reading whatsoever. It just gradually fizzles from stoich. to lean and then goes off the gauge altogether.

Just wondering if anyone knows what would be causing this? The gauge is wired up properly and all the connections are soldered and covered with heat shrink.

I have no idea what the problem is and right now it's starting to give me the S*&TS

Thanks for your help

[blind_elk]

So, it appears to be working initially, but then "dies" - is that correct? If so, then what you have described suggests that the mixture is going lean. I would suggest the fuel pump is dying after about 30 minutes, maybe overheating. What happens if you tromp it - the gauge should show rich.

How far down the exhaust is the Autometer sensor? Is it heated? What ECU are you running? Can you connect the gauge to the factory sensor?

[tdan]

Thanks for the reply. That is correct, it does work properly, then it dies off. Once it has gone off the "radar", it doesn't come back. Irregardless of whether I tromp it or not.

The sensor is about 30-40cm from the turbo outlet. It is heated via the positive and negative wires when the engine is initially turned on (cold engine start), then it gets the heat from the exhaust. I am running the factory R33 GTS-T ECU and have been told by autometer tech-heads that the gauge cannot be connected to the ECU as it will receive the incorrect signal.

So I have no idea what to do next. I thought maybe that the probe was dirty and I need to clean it with something, but it is a bugger to get at.

[blind_elk]

The sensor should be permanently heated. If the heating turns off, then the sensor will not be able to reach optimum operating temperature, and will not be able to give correct A/F indications.

Might be worth putting it on a dyno for a few minutes (after the gauge has "died") and see what the A/F is.

[tdan]

Cool, thanks for the hint. What I might do in the meantime is lift the bonnet and check the fuse that is connected to the probe and also the wiring. Maybe, just maybe, the fuse has gone and the reading is only just getting to the gauge. But I guess in that case, the probe would not give any reading at all. I think I'll just try a few things out and see what happens.

Also, do you think that it could be the factory sensor? Could the fact that the factory sensor is faulty, if it is, that it is sending the ECU an icorrect signal and the Autometer sensor is picking that up. Maybe I should also look into having the factory sensor replaced.

Well, time to try things out.

Cheers.

[Godzilla32]

Factory sensor wont have any bearing on what the Autometer one reads. Perhaps the Autometer sensor has issues and after some running it becomes faulty and doesnt output the correct signal? You should be able to test it for resistance i would think? Not sure of what you should expect to see though..

[tdan]

I just thought that if the factory sensor is buggered it will be sending the wrong signal to the ECU. Then the ECU would not be correcting the A/F ratio which inturn the Autometer sensor is picking up the incorrect signal from the exhaust fumes. Does that make sense?