Bad luck with 02 sensors?

[One Equals Two]

I bought my Talon 3 or 4 months ago knowing the CEL was on. The guy told me it was the rear 02 sensor, and after I pulled the codes (P0173 - generic fuel trim and a few others) they were consistent with what he said.

So I bought a universal one (bad move I know but I've gotten away with it before) and replaced it. The code went away but came back 60 miles later. Only the 173 code showed up. Also my mileage dropped from 24 ish to 16 during this time. I wasn't happy about the mileage, so I quickly dropped the money to get an OEM one (what I should have done in the first place).

Now the car runs much worse, and I get about 12 mpg. Also it now hesitates, has a harder time starting, and, yeah, I am not happy about this. CEL is back on with the same 173 code.

I checked the resistance on the 3 and 4 terminals on both of the sensors, and they were both off at 9 ohms for the universal and 5.5 for the OEM, compared to the recommended 12. I've cleaned the injectors and throttle body up, redid those gaskets, redid the heater hoses and replaced the starter. Actually, this was all done at my shop by the head tech (wouldn't BS me or he'd be fired, haha).

I am wondering if I just got two bad O2s in a row. And maybe it's just me, but I thought Bosch was more specific to Euro cars. I thought Mitsu's used Densos or something like that. I ordered this online as an "OEM O2 sensor" through our parts department, but it still came as a Bosch. Any help is appreciated, thanks!

 

[jrohner]

You have another issue if your car is running bad. The rear o2 sensor's only job is to turn on the CEL, it isn't used for running the car (it's just for checking that the catalytic converter is working). Figure out what's wrong, and if your CEL is still on after you get it running good, put a piece of tape over it. Do you have a logger of some kind? It would be nice to know if the ECU is getting a signal from the o2. Does your car have a cat still?

 

[forumboarder154]

If the CEL annoys you enough and you don't want to or pay for a $60 test pipe or $150 for a new cat. Go to the autoparts store and buy a spark plug non-fouler (around $6 I think) and screw it into your exhaust and then screw your o2 sensor after it to remove it from the exhaust stream. This will solve the CEL issue. The mpg issue may be from the cat being clogged or front o2 sensor needs replaced most likely. If you think it is something aside from an exhaust issue fuel filter, spark plugs, or spark plug wires possibly. Maintanence is the key especially when just buying it off somebody else.

 

[One Equals Two]

Well, the purge valve is being opened up (you can hear it, sounds like a arc from a bad spark plug wire) and it only started doing that after I replaced the 02s. Plugs and wires, air filter, etc, are all fine. Minus the cam seals, there's no issues with the car (fully inspected at my shop). I went over it with a fine tooth comb with the tech there as well.

I can only assume at this point it's the 02 sensor because it started running badly and getting worse mileage after I put it in. It only started running roughly after the 2nd 02 replacement, and it ran poorly immediately after I put it in. The CEL came on very soon after as well.

I am only wondering what the likelyhood of getting 2 bad sensors in a row is...and if the OEM sensor is really a Bosch. That's my question. If the parts outlet gave me a non OEM sensor (when it was listed as OEM), then I am going directly to Mitsubishi and screwing the parts vendors.