97 JGC Backfiring

[beepbeep]

1050999

I'm having a little trouble with my 97 Jeep Grand Cherokee Limited. It's got the 5.2 V-8, and all time 4WD. A week ago when I would stomp on the gas to enter the highway at about 3500 RPM it would start backfiring, I couldn't fix it during the week so I continued to drive it but on my way home from work last night it backfired all the time and had no power and is undriveable right now. I checked the codes stored in the computer and I recieve 12 43 21 55.

12= Battery has been Disconnected

21=Oxygen Sensor

43=Backfiring

55=End of codes



My questions are:



Which oxygen sensor should I replace? ($85 each)

Would a bad oxygen sensor cause this?

I have a long vacumm line that comes from under the motor and I don't know where it's supposed to go?

Any help would be great

Thanks in advance[addsig]

 

[CARDOC123]

1051105

Your best bet would be to buy a Hyanes manual and check out the vacuum routing, as this could cause the the problem and will surely cause the O2 code. And check all other vacuum hoses also. There may be a vacuum hose routing sticker under the hood also. You must be checking the code using the key on/off method. I don't know how many O2 sensors you have but I'm guessing at least two, one before the converter and one after. The one before actually determines the way the computer does its fuel thing, the one after just double checks and makes sure the first one is doing what it's supposed to and that the converter is doing it's job also. I'd go the hose route first, because like I said an air leak will cause both O2 sensors to read faulty. Hope this helps and good luck.[addsig]

 

[RufftyTuffty]

1052727

I had exactly the same problem.

It turned out to be the upstream O2 sensor shorting out....once replace viola....no more backfires [addsig]

 

[dingus]

1052736

yeah... i'd replace the O2 sensor[addsig]