97 JGC Problems

[beepbeep]

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



U.S.A.[addsig]

[Joker®]

No experience with a ZJ, but when my O2 sensor went bad on my YJ, the MPGs went to crap and lacked power when I'd hoss it. I'd say your O2 sensor is telling your computer that the air/fuel mix is lean and you're getting unburned fuel into the exhaust system.



My YJ has only one O2 sensor (before the cat), the newer TJ have two (before & after the cat). I have no idea how many are on a ZJ.[addsig]

[Tug-n-pull]

Do the o2 sensors have the same part #'s or are they different. If they have the same part # then buy one try in one place the if that is not the fix switch places. Just a thought! Tug[addsig]

[beepbeep]

I'll get the parts tomorrow in the morning, the part numbers are different (figures). I'll let you know what happens.



Thanks [img]modules/phpBB_14/images/smiles/icon_cool.gif[/img] [addsig]

[Quik8slvr]

i no longer have any o2 sensors, backfires occasionally but nothign regular[addsig]

[beepbeep]

Parts store isn't open yet, I was able to get the old ones out (pain in the A) now if the part store would only open. Quik8 if this only backfired once in a while I wouldn't mind but it backfires alot. If i give it 1/4 throttle she will backfire 30 times in 10 seconds, it sounds horrible, but now if I floor it I only have 1/4 of my power and it boggs down but won't backfire. One of the backfires yesterday was so powerfull the it blew my K&N off my intake hose. I just can't see the oxygen sensors causing this. I guess we'll find out in a couple hours.



Thanks [img]modules/phpBB_14/images/smiles/icon_confused.gif[/img] [img]modules/phpBB_14/images/smiles/icon_eek.gif[/img] [img]modules/phpBB_14/images/smiles/icon_evil.gif[/img] [img]modules/phpBB_14/images/smiles/icon_cry.gif[/img] [img]modules/phpBB_14/images/smiles/icon_frown.gif[/img] [addsig]

[CARDOC123]

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]

[beepbeep]

here's the latestest update. I installed the two new oxygen sensors reset the computer found that the vacumm line is really a vent for the front axle and the car is still running real rough. any more suggestions???????? [addsig]

[beepbeep]

After driving it for a while it seems to be right back where it was about a week ago. If i drive it easy (never more than 1/2 throttle or higher than 3000RPM) it runs fine but when i get on it it starts its bucking and backfiring again. The computer now only has error 12 and 43. Can anyone think of what else I should try. Thank you to everyone that has help me already.[addsig]

[CARDOC123]

I haven't ran across anything this new backfiring that wasn't vacuum or sensor related. I think that now might be a good time to take it to someone that can hook into the computer and see what's happening while it's running. I'm thinking maybe timing or computer getting bad info and messing with the timing. Of all I know about vehicles it could be cam or crank sensors, or maybe coolant temp sensor. At any rate I'd have to hook it up to see what's going on. Sorry and good luck.[addsig]

[beepbeep]

thanks cardoc, what I think I'm going to do is wash it, vacumm it, bring it to the dealer and trade it in and get an 03. It's got over 100k on it and i've just been puttijng it off for about a year now. Thanks for your help.[addsig]