i recently hooked up an AutoMeter Air/Fuel gauge to my car (i have a Civic coupe).. the problem i'm running into is.. the readings aren't steady. The readings tac, from one bar rich all the way to lean and back and forth~ it doesn't give me one specific bar reading. one of my friends said that it could be that Vtec is affecting the readings.. another said it was the gauge wire i'm using for the power. (i'm currently running a 14 gauge wire from my headlight switch). how would i go about fixing this problem?? does anybody know??

 

thats the way its supposed to be. its just a light show, doenst give you accurate readings. and the reson it fluctuates is because the o2 sensor fluctuates as well.

 

If you want a good stable reading go with a wideband O2 and a digital readout... Even the Halmeter AF30 jumps around but it is a little more accurate then an Autometer... As tnbigdawg said they do tend to jump around a bit (not giving an accurate A/F)... Latez

 

it should give a steady reading under heavy acceleration or so I've read. when you're just ideling or at a steady engine speed the ECU making adjustments for lean/rich throws the meter back and forth like that

 

you're right. But still, its not that accurate.

I have one, but I just enjoy the "Christmas lights".

 

It fluctuates because stock O2 sensors can't accurately determine air/fuel ratio beyond "rich" or "lean". So the computer alternates the fuel injector pulse width so the air/fuel ratio is constantly fluctuating rich/lean/rich/lean/rich/lean/rich/lean/rich/lean/etc...

Only when you go to wide open throttle does the reading steady down, because the computer quits altering the air/fuel ratio by the O2 sensor and instead goes with a stored value based on air temp and pressure. The only reason they do that is to prevent detonation at WOT - fuel economy comes in second at that point.

About the only thing I found mine useful for was to tell me when the O2's were going bad. As they deteriorate, they don't fluctuate as fast, so you know you need new ones.

Stonebreaker


[Modified by Stonebreaker, 5:04 AM 12/24/2002]

 

ok... soo does that mean... when i open the throttle up and it tac's green and stays there.. (i mean really tacs green.. its like 2 to 3 bars from being completely rich) does that mean my car is running rich???

 

who knows the AF gauge just thows ECU code 1 when I have it installed. So I took it out. the gauge is not very accurate. get on a dyno w/ wideband= much more accurate.

Good Luck.

 

It doesn't mean a thing. The stock O2 sensors just aren't precise enough to tune the air fuel ratio by millivolts. That's why there's a range of green LED's on that gauge - it can tell if you're in the ball park, but not exactly what air/fuel ratio you're running.

These gauges were originally designed to be used with carburated engines. You buy an O2 sensor, weld in a bung on your exhaust, and use the air/fuel gauge to help select the right jets for the carb. And even then, it just gets you in the ball park.

Don't feel too bad - I bought one myself thinking I could use it to fine tune my fuel pressure, not realizing it wouldn't work. Because I had the Cyberdine unit, which is just a straight bar graph instead of round like the Autometer piece, everyone would see the bar graph jumping up and down and thought I had a radar detector. People would zoom by in the left lane, see the A/F gauge flickering up and down in my gauge pod, and slam on the brakes and drop in behind me. It amused me enough that I kept it in there till I needed the spot for the nitrous gauge.

Stonebreaker

 

ok.. cool~ thanks people!!

 

I don't know why everyone is so quick to trashtalk a standard 02 sensor and a gauge. Yes, I agree it's no good for standard closed loop driving, but the second you go WOT, you're in open loop and it will stay steady. I wouldn't use it to tune the perfect mixture, but it could be a nice warning if you suddenly go lean at WOT - it'll let you know faster than an EGT anyway. So, if you can't afford a wideband, it's better than nothing.

There's also the argument that if you have enough mods to possibly create a lean situation, you should be running good diagnostic equipment - and that's a valid argument.

But either way, I wouldn't call them "useless", just useless most of the time

and for the record, I'll be running a wide-band

 

the autometer A/F is only really sensitive in the stoich area.. in lean or rich the sensitivity drops to near useless. It bounces because of damn emmisions. The ECU is constantly reading the O2 sensor(s) and adjusting the amount of fuel to get honda's spec'ed A/F going. Good for emmisions, gas milage, etc.. but sucks for performance