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Air/Fuel Gauge Issues

This is a discussion on Air/Fuel Gauge Issues within the General Help forums, part of the LSx Technical Help Section category; The car is a 1998 Z28 with stock headers (but not for long) I just installed an AutoMeter Air/Fuel ratio ...

  1. #1
    I Fixed Da Rear jimbo98z's Avatar
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    Mystic Teal
    1998 Z28 M6

    Air/Fuel Gauge Issues

    The car is a 1998 Z28 with stock headers (but not for long)

    I just installed an AutoMeter Air/Fuel ratio gauge and I can't get it to work. I went to the purple/white stripe wire under the steering wheel and it's constantly reading all the way lean. I recently had the car tuned, and set the air/fuel to around 13 at idle. Even when I rev the engine, there is no change in the reading. Would the purple and white wire under the dash be the right wire, or do I have to go under the hood to the wire coming right off of the O2 sensor?

    Any help is much appreciated

  2. #2
    No 55mph 1QuikWS6's Avatar
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    You should have taken your wire to the gage right off the wire from the O2 sensor. Casper's Electronics makes a PnP adapter that plugs in between your O2 sensor and the wire connected to it and also has a pigtail coming off that goes to an A/F gage to make things easier on ya.

    BTW, you know that the AM A/F gage is really nothing more than a 'light show'? It does not have a digital readout and is using the signal from the stock narrowband O2's - which are not very accurate to begin with.

    If you truly need/want an accurate A/F reading you will have to spend the $$ and go with a wideband O2 setup such as Innovate, AEM, or Dynojet. These start at around $300 and more...

    Personally I have the Innovate LC-1 with the XD-16 Programmable Gage shown below:



    -Jay-
    Last edited by 1QuikWS6; 03-09-2006 at 02:41 AM.

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    I Fixed Da Rear jimbo98z's Avatar
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    Mystic Teal
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    Yes, I know the gauge isn't very accurate, it's mainly so if I see something go way wrong, I can shut it down. Being a college student, a wideband isn't in the budget right now.

    If I were to splice the wire in as opposed to buying a pigtail, does it still go to the same purple with white stripe wire coming off of the O2?

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    Senior Member Danger731's Avatar
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    dude don't go 1/2 way and give yourself false sence of security

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    Member Transam388's Avatar
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    I hate to just chime in but like everyone else has said, if your going to do it, do it right. I had the AM guage and that was a light show and was nowhere near being an accurate show of what the A/F ratio was. I actually was leaning out on the top end and that thing never showed any sign and actually tended to show I was rich. So anyway I would say spend the cash and do this once before wasting your time and money. Good luck with it!
    98 T/A: HPE 5.3 Heads, 238/242 113 cam, Kooks 1 7/8 stepped LT headers, Custom Y pipe, Cut out, Borla, NW 90MM TB, FAST 90MM Intake, TB Bypass, Under Drive Power steering and Crank, 150 Dry NOS, Yella Terra rockers, 3400 TC, HPE tuning,

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    I Fixed Da Rear jimbo98z's Avatar
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    So does anybody want to answer my question, or is everybody just going to tell me how useless my damn gauge is?

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    Member Transam388's Avatar
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    Get an A/F guage pigtail plug for roughly 19.00. This harness enables you to hook up your Rich/Lean gage without cutting any wires. This unit installs between the factory wiring and the front oxygen sensor. Harness uses OEM connectors and automotive spec wiring. Then connect the one wire that comes off the plug to the wire from the A/F guage. Does this make you happy? So be it for people trying to give you advice to keep you from messing up.

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    I Fixed Da Rear jimbo98z's Avatar
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    Mystic Teal
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    Alright, thank you for answering my question.

    I know you guys were just giving me advice, and I know I need a wideband, but I got the gauge for free. I have a 3 gauge pod and I already had Oil Temp (with a switch to go from tranny to engine) and a more accurate water temp gauge. A buddy of mine had the gauge in his garage and had not put it in, so I'm just putting it in to fill the hole in the pod. I'm going to get a wideband and a digital gauge this summer when I have the money, but I figured, why not put the free AM gauge in to fill the hole until I get the wideband, even if it is "just a lightshow"

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    Tech Junkie hammertime's Avatar
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    Quote Originally Posted by jimbo98z
    The car is a 1998 Z28 with stock headers (but not for long)

    I just installed an AutoMeter Air/Fuel ratio gauge and I can't get it to work. I went to the purple/white stripe wire under the steering wheel and it's constantly reading all the way lean. I recently had the car tuned, and set the air/fuel to around 13 at idle. Even when I rev the engine, there is no change in the reading. Would the purple and white wire under the dash be the right wire, or do I have to go under the hood to the wire coming right off of the O2 sensor?

    Any help is much appreciated
    Why have the car tuned to run rich at idle? If you really had it tuned to 13:1 at idle, thats way to fat for a stock engine. You are giving up power and throttle response.

    A stock O2 sensor will not read 13:1 properly, it will always show up rich. As others stated, the stock sensor only reads properly in a very narrow window - pretty much above the range you claim to be running at.

    You really would want your A/F ratio to be pretty close to 14.7:1 at most operating conditions (idle, cruise, part throttle, etc). It should go up when you are coasting and there is no demand for fuel, and it should go down to around 13:1 at WOT.

    Not here to flame you, just letting you know what you are saying doesn't add up.

    Good luck!

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    I Fixed Da Rear jimbo98z's Avatar
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    Mystic Teal
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    When I first plugged the car in, it was down somewhere in the low 12's for Air/Fuel. I'm going to get the car dyno tuned after I put the headers on, and get everything set exactly where it needs to be

  11. #11
    No 55mph 1QuikWS6's Avatar
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    I thought I DID try and help you with the wiring problem way up in my post?

    Casper's Electronics makes a PnP adapter that plugs in between your O2 sensor and the wire connected to it and also has a pigtail coming off that goes to an A/F gage to make things easier on ya.
    Whis is same advice that was repeated later on. You can, however, for free - just splice into the wire you referenced down by the O2 sensor without using the adapter pigtail.

    You're on the right track as far as the tuning goes - do as many mods as you can first - then get it tuned for the combo at same time. Just have to watch what mods you do - as some will require immediate attention as far as tuning goes. Should be OK if you're just adding headers right now (unless of course you plan to delete cats, remove rear O2's, and remove EGR/AIR). If you are doing this it won't hurt the car to run without them, but you'll throw an SES light with a bunch of codes for the missing items until you have them programmed out - just annoying.

    I can understand where you're coming from as far as spending the $$ on expensive parts. I think some of us 'older' guys forget what it was like when we were young. Heck, my (3) kids are grown now and I'm in my 3rd childhood already! My wife lovingly says I'm in my 'It's all about me' phase

    -Jay-
    2000 Phoenix WS6 Trans Am
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