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Old 03-18-2014, 12:21 AM   #1
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o2 sensors are making my life a living hell

Ok so I would like to start off by saying sorry if this is a beat down subject.

I have a 2002 ZX3 and today while driving about 35mph she started missing TERRIBLY. Well I limped back home and scanned it and got a downstream o2 sensor code, an o2 heater bank code and a cylinder 3 and 4 misfire code. So my question is, would a failed sensor cause the car to run like absolute poo? I looked up a few threads on the problems that bad sensors create but none of em directly stated that they caused bad misfires. I need help soon because its starting to get nice in my neck of the woods and I wanna cruise soooooo bad.

Thanks in advance to those who can help.


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Old 03-18-2014, 12:23 AM   #2
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Moved to the Technical Chat area



Yes a bad O2 sensor can make it misfire and run really bad, I know cause it's happened to me before. You may also want to check you coil pack plug as the wires can get pulled out cause a misfire as well.
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Old 03-18-2014, 01:25 AM   #3
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Plug wires are all good. Double and triple checked them as soon as it started. But thank you for that confirmation. Its just irritating because i just fixed it and now it starts acting up yet again I wish I could just catch a break already.
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Old 03-18-2014, 01:55 AM   #4
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Sleepyboy was referring to the wires that plug into the coil, not the spark plug wires.

Looking that connector over & it's wires as well isa good step to take. Plug/connectors/wires can cause problems. Sometimes that harness is damaged a ways back from the coil.

Pulling the coil & looking it over for cracking is another common check - any cracks found, it's toast.

Luck
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Old 03-18-2014, 02:15 AM   #5
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Do the wiggle test while it's running, if it clears up and runs smooth or starts sputtering then you found the problem.
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Old 03-18-2014, 03:19 AM   #6
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[QUOTE=sailor;5678418]Sleepyboy was referring to the wires that plug into the coil, not the spark plug wires.

Ohhhh haha. Another case of me not reading the fine print. Thank you for pointing that out and I'll try the "wiggle test" during the daylight hours because my neighbors dont take kindly to me firing up the hatch this late (or early) lol. Shes kinda loud
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Old 03-18-2014, 04:48 AM   #7
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Too add to what's been stated,
While an O2 sensor can make a car run poorly, this generally only pertains to the Primary (front) O2 Sensor.
The Downstream (secondary) is only there to measure Catalyst efficiency. Or basically, to make sure the cat is working.

A 3/4 misfire would sound to me more like either weak fuel injectors or low fuel pressure.
The cylinders start at the cam gears, 1,2,3,4. And being the fuel comes in at #1, that means 3/4 are at the end of the line. But don't get it in your head that's the problem, it might not be.
It could also be the intake manifold has a damaged gasket on 3/4. If they've never been changed, odds are they're old and brittle. With the right tools, it's a hour job to change them (the bottom bolts are a PITA, swivel ratcheting wrenches help).
Along with that are injector O-rings. If the injectors have been out, it's pretty easy to nick a gasket. They can cause a slight vacuum leak that isn't picked up by normal means (carb cleaner).
EGR isn't out of the question either. Lets say the gasket is damaged at the valve. That won't throw any EGR codes, but it will have a lean misfire and probably poor idle.

Basically, look at the integrity of everything on the 3/4 side of the engine. If anything is damaged, repair/replace it.


You should download the guides I have stuck at the top of this section 'further understanding ...'. It'll explain better than I care to about how the misfire thing works.
But in a nutshell, the ECU doesn't monitor if a spark plug actually fires. It measures the result of when it should have fired. So it's not a dead to rights case of it being a spark issue.
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Old 03-18-2014, 06:53 AM   #8
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I too saw the word downstream, which should not affect engine running unless it means something has damaged the cat. If the matrix inside was shattered that might produce some wonky effects.

The upstream O2 is the one that affects engine running when it goes south.
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Old 03-18-2014, 10:45 AM   #9
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Thank you for the replys fellas. This has given me a great place to start looking. Ill keep ya'll posted as i find out whats wrong.
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