Air fuel gauge flaking out...
 

Hey all... wanted to get some opinions on this. I have an Autometer Air/Fuel Gauge in my 3rd gen. It has been doing some odd things for quite some time now and I'm finally getting itchy to solve this problem.

Basically what happens is, the gauge will show that the car is running STOICH when you first start the car and hit the gas. As you drive it, for some time... if I press the peddle, it will no longer make it all the way into stoich, but will gradually begin to shift it's way left to LEAN.

At first I thought this was an engine performance issue, but this has been ruled out. If I go into my PowerFC... I can read the sensors and the O2 reads perfectly... when I take my foot off the gas it hangs around .1, when I hit the gas it goes up to .8-.9. But the A/F gauge display will gradually deteriorate to the point it doesn't even register this change.

So I'm trying to figure out if this is a wiring issue or if I should just buy a new gauge. It may be that simple. But I wanted to see if anyone had any suggestions... as to why it would work and then slowly stop working. Before I go and spend money on a new one.

Thanks,
Steve

I hope you are not tuning your car or something based on that a/f gauge. That gauge has never been accurate and all it is, is just a light show.

Amel

No, we haven't been tuning it based on that gauge... but I would hope that it is at least accurate enough to give me an indication if any problems arise. Instead of having to do a sensor check on the Power FC. So, I'd like to get a gauge in there that works.

a/f is useless as most people will say...throw in a wideband :) aren't they like $400 from aem?

Just to clarify, A/F gauges are not useless. Using an A/F gauge with a narrow band O2 sensor is useless.

It's the sensor that makes the gauge accurate or not.

Perhaps there is a little confusion. I'm not interested in a super-accurate gauge.. if I tune, we will hook up to something much more accurate than the gauge. But, as I said in the first post... it displays the approximate value very well, but deteriorates for some unknown reason.

I guess I was hoping to find out if anyone could think of a reason why an A/F gauge would work some of the time... but gradually change over time... like, over the course of driving the car for the day? is it a grounding issue? wiring? a bad gauge?

thanks.

replace your o2 sensor, you'll see the difference. I got one from advance auto parts for 18 bucks.

Amel

Hey Amel, thanks for the reply... the O2 sensor is good though... we've tested it... and it's reading the right values. So... it has to be something leading up to the gauge or the gauge itself. I just don't want to spen $75 on a new gauge if it's some wierd issue, like grounding, or something....

a/f ratio gauge is not suppose to work unless your temp is at least 300 degrees, and even at that they are suppose to work at only WOT. now note that i said suppose to work, in reality they are crap, i know and i have one haha. if you do go wideband, go motec. sure its 1200-1400 bucks but its one of the things id rather not skimp on. sure you can make your own but then again, your making it yourself... i have heard horror stories about the DIY stuff from even eletrical engineers (remember these are the uber dorks of the tech community haha, im just kidding).

serioiusly though, I would go with motec if you have the means. your risking your 3-5k engine+turbos on 400-600 dollars savings i would suggest perhaps finding a few guys and making a club and having everone chip in for one.

Note: on pump gas (unleaded gas) the sensor only is worth about 500 hours. on leaded race gas, its only good for about 50 hours. and the sensors cost about 400 bucks, if your entire wideband system cost 400 bucks... i would rethink how well it was made adn what materials went in to it...