Keeps saying "bad o2 sensor"!

[stinkiestbink]

i have a 92 xlt and it started running rich as hell. when i shift from drive to reverse, it stalls. it idles erratically and burns tons of fuel. when it first starts, a pile of black smoke comes out. i replaced the o2 sensor and mass airflow sensor and it still reports back that i have a bad o2, (garage has done a bunch of diags). If i unplug the MAS, it runs fine, but still eats a lot of fuel and pings under load. i have been running like that all winter and spring just to get by. all i can think of now is that there is some sort of disconnect between the o2 and the computer. i fear the dealer! any ideas would be appreciated.

thanks guys.

 

[Fordmandan87]

clean the $h!t out of the maf and consider the option of getting a new one. pull out a plug and inspect it and after all that make sure your not running ****ty gas the reason the o2 sensor is throwing a code is it got turned to $h!t with all the crap it is being fed by the exhaust btw i work for ford

 

[stinkiestbink]

i first cleaned the MAS and it didnt help. i then replaced it, and it still ran the same. i then unplugged the o2 and there was still no change. i now have a super clean MAS and a brand new o2 with the same symptoms.Would the engine run differently with the 02 unplugged? when i unplug it, there is no change, (and that is with the old one and the new one).

 

[redneck21]

Did you unhook the (-) on the battery to reset the ecu.

 

[stinkiestbink]

not since the new o2 sensor. how long does it need to stay unhooked for?

 

[MrShorty]

Technically, there's no such thing as a code for a bad O2 sensor. codes 171-183 indicate that the computer saw a problem in the O2 sensor signal, but the computer has no way of knowing if it's a bad o2 sensor, or a broken wire, or a bad MAF or other sensor, or something wrong with fuel delivery, or a vacuum leak, or a misfire, or an exhaust leak (and so on and so forth). I might suggest reading Glacier991's "primer on computerized engine controls" thread to get a basic feel for how the MAF, HO2S, fuel delivery, and other sensors work together to optimize fuel mixture.

You say that your mechanic has done several diags. It would help to know which diags have been done, so we don't just recommend something that has already been done.

1st question: which O2 sensor code are you getting? Both CM and KOER, or CM only? Pass KOEO? (If that doesn't make a lot of sense, review my notes on pulling EEC-IV codes in the EEC-IV forum)

2nd question: By the book, just about all O2 sensor code diagnosis starts with a fuel pressure test. Has this been done? what results?

3rd question: Is the engine running rich or lean? Your post suggests that it is running rich, but I can't be certain. Is the O2 code also for a rich condition, or is it indicating lean?

4th question: Have you checked the wiring between the PCM and the O2 sensor?

 

[stinkiestbink]

holy crap! all he told me was that it was reporting back "a lazy o2 sensor".

1. can i go to Advanced Auto Parts to get the code read?
2. i dont believe this has been done. would it run normal when the MAF is unplugged and the pressure was low? it seems to run fine, just bad mileage and pinging.
3.i assumed rich because of the excessive fuel consumption and black smoke.
4.going to check the wiring next. it is just so buried in there that it may take a while.
5. thanks a bunch for the help!

 

[redneck21]

Auto zone can only pull OBDII ur being a 92 it's OBDI. Try and unhook the (-) for like 30 mints it is a long shot but sometimes when something messes up even with the new part in it will still read it as bad.

 

[MrShorty]

Sometimes the guys at the parts store can read OBD-1 codes, it usually depends on how knowledgable the guy behind the counter is. Because of this hit or miss (mostly miss) aspect of getting EEc-IV codes read for free at the parts stores, I prefer to tell people to learn how to do it themselves. If you read my notes on pulling EEC-IV codes thread and BrooklynBays EEC-IV code list thread (both in the EEC-IV forum) and the other thread in the Under the Hood forum, you should be able to grab a paper clip (or other jumper wire) and pull the codes yourself.

 

[boggs1227]

i have a 92 xlt and it started running rich as hell. when i shift from drive to reverse, it stalls. it idles erratically and burns tons of fuel. when it first starts, a pile of black smoke comes out. i replaced the o2 sensor and mass airflow sensor and it still reports back that i have a bad o2, (garage has done a bunch of diags). If i unplug the MAS, it runs fine, but still eats a lot of fuel and pings under load. i have been running like that all winter and spring just to get by. all i can think of now is that there is some sort of disconnect between the o2 and the computer. i fear the dealer! any ideas would be appreciated.

thanks guys.

...if your blowing out black smoke would'nt that be a bad fuel pressure regulator,resulting in bad fuel comsumption and possible o2 problems ?

 

[stinkiestbink]

alright, i will read up and get the codes myself. problem is that i am leaving for a week. i will do it on friday and report back.

thanks a lot guys! I thought all hope was lost and was ready to sell the thing!