Will bad oxygen sensors show as a engine light?
 

I was wondering if you have bad oxygen sernor or sensors does it show as a engine light? I failed emissions and I may suspect a bad o2 sensor but I have no engine light on.

Usually, yes. I hestate to say always though. Have you considered things like malfunctioning emissions equipment or clogged cats? It could something pretty simple.

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1984 1/2 GT350 (#842 Hatchback w/ T-tops), 302HO, Comp cams Xtreme Energy cam, Carter 625cfm carb, Weiand Stealth intake, MSD distributor, MSD coil, FMS 9mm wires, 1 5/8" MAC unequal shorties, 2 1/2" MAC Prochamber H-pipe, Flowmaster 2 chambers, KYBs, 16"x8" 4 lug Cobra Rs, Falken 245/45ZR16s

If there's carbon built up on the oxygen sensor it probably won't send a signal but it will read incorrectly. What did you fail in? CO and HC?

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'84 Mustang 5.0 T5, FMS aluminum radiator & 180* thermostat, 1 5/8 shortys/2.5" duals, '88 GT tail lights and wheels, Holley 4160 4 BBL, smog pump idler, now with hi-po collapsed lifters in #3 or #4 :)

I failed for nox, double the allowed limit. Car has 62k, engine pretty much stock, recent tune up,I only put about 2k on it in the last year. Has mac cat h-pipe.

Yes the check engine will come on. It will soon start wander around when idling and no settle in once it gets warm. Replace them with NASCAR sensors.



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PALADIN
"COME CORRECT"

Where do you get NASCAR sensors??

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a bad oxygen sensor will not trigger the chech engine light,i speak from personal experience,i had a 87 lx that had hesitation problems and backfiring,i went ahead and did a code scan,the scan detected the problem with the oxygen sensor,turned out the ceramic in the sensors were broken,once i replaced them it ran smooth again.hope this helps.

No, most of the time the check engine light means nothing more than a bad oxygen sensor. Toss some new one in, can't recommend a brand though, OEM?

I went to NAPA and used the same sensor they put in the sprint cars for ford engines. I changed them because of the fuel I used. when I start to see trouble of any kind I've learned to monitor the O2 sensors. This is the case when using leaded race fuels. some may disagree but it works for me.

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PALADIN
"COME CORRECT"