How to spot a bad O2?

[cmptrphreak]

How would I know if my o2 sensor was bad. I do have a logger so I can look at the voltage. My maf is descreened if that makes a difference with stock turbo and injectors. thanx

 

[leakyfaucet]

How would I know if my o2 sensor was bad. I do have a logger so I can look at the voltage. My maf is descreened if that makes a difference with stock turbo and injectors. thanx

Not sure how to tell a difference with o2s.. I believe if the o2 signal doesn't cycle back and forth and idle and cruise, it is messed up.

MAF descreening will make a difference, it will make the motor run leaner, it will not be able to detect as much air coming in as is actually coming in.

Hope that helps

 

[BoostedDSMman]

I always change my O2s at the 30k mile mark. How many miles are on your car? When was the last time your front O2 sensor was changed? If it hasn't been changed by you, it probably would be a good idea to buy a new one from Mitsu.

 

[a_scobel]

They say O2 sensors are good for around 60k miles.

 

[Old Mitsu Tech]

The median range on an o2 sensor is 450 mv give or take. Above that, it's rich. Below that, it's lean.

If your o2 stays rich or lean, you can spray some propane or something like that into the intake and observe your o2. If it's lean, it should go full rich which is around 1 volt.

If it does not, then it's lazy and should be replaced.

If your o2 is sitting on rich side, pull the pcv hose and make it go lean. If it doesn't drop, then again it's lazy and should be replaced.

It should swing back and forth. This is for the catalytic converter's benefit.

You have to have a momentary rich condition in the catalyst followed by a momentary lean condition to burn the rich mixture in the catalyst.

It's an emissions thing.

Good Luck

 

[cmptrphreak]

My car has 43,000 miles on it only. Dont thing its ever been changed but has been taken off a few times. Here's some of logs at idle and at 3000

Time coolant temp RPM O2 TPS
257.23 195 812.5 0.12 9.8
257.29 195 812.5 0.1 9.8
257.36 195 812.5 0.1 9.8
257.42 195 812.5 0.1 9.8
257.49 195 812.5 0.1 9.8
257.56 195 812.5 0.1 9.8
257.62 195 812.5 0.1 9.8
257.69 195 812.5 0.1 9.8
257.76 195 843.75 0.12 9.8
257.82 195 843.75 0.14 9.8
257.89 195 843.75 0.23 9.8
257.96 195 875 0.57 9.8
258.03 195 875 0.82 9.8
258.1 195 875 0.9 9.8
258.16 195 875 0.92 9.8
258.23 195 875 0.94 9.8
258.3 195 875 0.94 9.8
258.36 195 875 0.96 9.8
258.43 195 875 0.96 9.8
258.5 195 843.75 0.96 9.8
258.56 195 843.75 0.94 9.8
258.63 195 843.75 0.94 9.8

259.84 195 812.5 0.94 9.8
259.91 195 812.5 0.94 9.8
259.97 195 781.25 0.94 9.8
260.04 195 781.25 0.94 9.8
260.11 195 781.25 0.92 9.8
260.17 195 781.25 0.9 9.8
260.24 195 750 0.88 9.8
260.3 195 718.75 0.82 9.8
260.37 195 656.25 0.74 9.8
260.44 195 625 0.61 9.8
260.5 195 625 0.39 9.8
260.57 195 656.25 0.27 9.8
260.63 195 656.25 0.23 9.8
260.7 195 687.5 0.2 9.8

time| accel enrich| RPM| I P/W|| Knock o2 feedbak| o2| timing advance
84.66 0 3000 1.79 0 144.53 0.92 39
84.8 0 3031.25 1.79 0 139.06 0.86 39
84.94 0 3031.25 2.05 0 133.59 0.8 38
85.08 0.39 3093.75 2.05 0 128.91 0.94 39
85.22 0 3093.75 1.79 2 122.66 0.92 37
85.36 0 3156.25 1.79 1 117.19 0.88 39
85.49 0 3156.25 1.79 0 111.72 0.76 39
85.63 0 3156.25 1.79 0 107.03 0.59 39
85.77 0 3187.5 1.79 0 101.56 0.88 39
85.91 3.91 3156.25 1.54 0 95.31 0.43 39
86.05 0 3156.25 1.28 0 105.47 0.29 39
86.19 0 3125 1.79 0 117.19 0.25 38
86.32 0 3156.25 1.79 0 125 0.78 39
86.46 0 3187.5 1.79 0 119.53 0.86 39
86.6 0 3125 1.79 0 114.06 0.57 38
86.74 0 3125 1.79 0 120.31 0.72 39
86.87 0 3125 1.79 0 114.06 0.88 39
87.01 0 3125 1.79 0 109.38 0.45 39
87.16 0 3125 1.79 0 119.53 0.31 39
87.3 0 3125 1.79 0 120.31 0.9 39
87.44 0 3125 1.79 0 114.84 0.88 39
87.57 0 3093.75 1.79 0 109.38 0.82 39
87.7 0 3093.75 1.79 0 103.91 0.61 39
87.85 0 3031.25 1.54 0 110.16 0.29 39
87.99 0 3031.25 1.54 0 120.31 0.27 39
88.13 0 2843.75 1.28 0 100 0.88 38
88.27 0 2562.5 1.28 0 100 0.7 38
88.4 0 2343.75 1.28 0 100 0.8 37
88.54 0 2093.75 1.28 0 100 0.86 41

 

[timm98gst]

easiest way to tell is if your check engine light comes on - and you will get really bad gas mileage

 

[polonez]

Well mine only cylces when cruising..... and it doesnt cycle al lthe way to the bottom of each side... at idle it doesnt really cycle
could mine be gone?
no CEL

 

[cmptrphreak]

Polonez . We had those in poland wierd cars. jsut like fiat 126 even smaller than the geo metro. sorry for being off topic. No cel Im just checking because i also getting phantom knock like crazy when I gun it a little bit.

 

[polonez]

Yeah what I wouldnt give to get a maluch in north america....
Im from szczecin .. .how bout u?