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Will an 02 sensor do this?

J

jeepman121

NAXJA Forum User
Location
Ohio
I know the sensor is bad, but when I start the Jeep cold and take off it falls on it's face...liking it's starving or flooding with fuel. I've never had an 02 do that before, but they were older Jeeps too. This is a 99 4.0
 
Don't think so. O2 input is not used until engine warms up and goes into "closed loop".

How is it once warm? Are you getting any other codes?
 
Yes it can, Jeeps with heated O2s go closed loop pretty fast and it can cause you problems if it is getting lazy, does it clear up within the first mile or so? If so your front O2 might be the problem
 
The only time my XJ was "falling on it's face" I ended up replacing the catalytic converter...vrooom!!! A clogged cat will rattle at low speeds or if you tap the sides. It'll also glow red hot at night (mine was doing both). I ended up having to replace the muffler too because a bunch of the honeycomb crap had gotten into it as the cat was disintegrating.
 
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Trying to troubleshoot a problem when you know that you already have a problem can result in the chasing of your tail.

Replace your oxygen sensors. Both of them; if one is bad, failure of the other one is not far behind. They don't last forever, most go between 100k and 150k, depending on the efficiency of your engine.

I recommend using NTK for your 99. Widely available and not that expensive.
 
jeepman121 said:
I know the sensor is bad, but when I start the Jeep cold and take off it falls on it's face...liking it's starving or flooding with fuel. I've never had an 02 do that before, but they were older Jeeps too. This is a 99 4.0
Click to expand...

If the O2 sensor is not connected, then no it will not cause your problem. But it should set off a CIL light and code. If it is bad, and is connected it might cause that problem.

If the problem is temperature related test the two temperature sensors first. Then test the TPS and the CPS. You could for instance preheat a suspect sensor like the TPS or CPS before you start the cold engine!:D
 
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CEL did come on and it reads bank 1. It only falls on it's face when cold for about 10 seconds, however when warm it idles like a turd and sometimes while coming to a stop it REALLY starts misfiring and nearly stalls. Vacuum line maybe??
 
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Then either the sensor is bad, bad heater in the sensor perhaps, or the 12 Volts to the heater in the sensor is missing (fuel or relay), or the wiring is damaged.
 
Had a similar issue with stalling and misfire. I also have a 99. Check the fuse in the panel under the hood. If its blown, it does stall and misfires. Fuse should be first row under the relays, don't know for sure which one on that row (may be the one on the left as you face the front of the car?), but it should be a 15 amps one. In my case, the wires from the o2 downstream (cat one) came loose and were shaved by the drive shaft, which caused a short and blew the fuse. Of course I found out about the damn fuse after I bought and replaced the o2 sensors...

Also, as people mentioned here, get ntk o2 sensors (napa carries them for example, 70-ish each). I bought bosh initially and they just don't work well with this engine, threw cel codes like popcorn. But from what I know, bad o2 sensors shouldn't cause engine to stall and misfire, but would make your jeep's mileage crazy low.
 
If the electric heater is bad in the O2 sensor, it will cause the same problems, just like a blown fuse that feeds power to the heater in the O2 sensor.

Prom3theus said:
Had a similar issue with stalling and misfire. I also have a 99. Check the fuse in the panel under the hood. If its blown, it does stall and misfires. Fuse should be first row under the relays, don't know for sure which one on that row (may be the one on the left as you face the front of the car?), but it should be a 15 amps one. In my case, the wires from the o2 downstream (cat one) came loose and were shaved by the drive shaft, which caused a short and blew the fuse. Of course I found out about the damn fuse after I bought and replaced the o2 sensors...

Also, as people mentioned here, get ntk o2 sensors (napa carries them for example, 70-ish each). I bought bosh initially and they just don't work well with this engine, threw cel codes like popcorn. But from what I know, bad o2 sensors shouldn't cause engine to stall and misfire, but would make your jeep's mileage crazy low.
Click to expand...
 
If weather and my schedule permits, I'll let you guys know what I find out. - This damn Jeep is pissin me off!!! The clockspring went out so I have no horn, cruise, or airbag. -and now my license plate light wiring went bad. I need to finish welding the floor pans back in my 95. -and If I was rich, I'd have my 92 5 speed safe to drive. While I'm talking about these Jeeps, I've noticed on all 3 of my XJ's none of them have ever had the dash light showing work when 4wd is engaged....Is that common? Or just bad luck?
 
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