Ricoswave

iTrader: (5)

So I am looking for the expected normal voltage range for my Evo 8 on the front 02 sensor. The car is down on gas mileage, seems very boggy, and sounds different. Long story short I am trying to find some specs on the OEM upstream sensor, so I can troubleshoot it before I try changing it. I have observed some odd looking waveforms on the scan tool. Any help would be great.

chrisw

iTrader: (2)

if the fuel trims are slow to respond when you first start the car in the morning, or when in closed loop, the AFR's go super rich to super lean for longer periods of time, then most likely your front O2 sensor is failing.

A quick check would be to enable the rear o2 sensor with a test pipe or high flow cat. If you DO NOT get a CEL (within a reasonable amount of time) then your front sensor is failing. This was how I found my bad sensor.

Ricoswave

iTrader: (5)

The car is surging horribly during cold starts ( I let the car warm up for a minute or so and then drive off, and it still surges at parking lot speeds). Two minutes down the road the car will clean up a little, but still feels noticeably "off". When you get into boost hard it seems like the car is fine. My issues are mostly part throttle and during spool.

I'm going to take a much closer look at the fuel trims and voltages today. I would put a test pipe in, but I am fairly sure the rear 02 is being ignored by the car after being tuned.

Ricoswave

iTrader: (5)

So it would appear that my 02 sensor will not hit .9 volts on the high side of the wave, and the cross counts are pretty slow. I compared them to the upstream 02 sensors on my girls Outlander, and her sensor fires way faster, and peaks right around .9 volts when warm at cruising speeds. At this point I am going to replace the sensor and report back. I hope this resolves my issues.

DSMolition

iTrader: (17)

let us know, my car is doing almost the same thing. it goes from .000 to .859 then it will stick at .39 for a while even when the rpms change. It is pretty erratic. My wb says 10.00 going down the road at 55.

Evo9_Dubai

Sorry to jack your thread..

I have the same issue, and I bought an OEM replacement sensor. Although when I came to replace it, I noticed that the plug on the vehicle harness is none existent, so I'm not sure which color of the vehicle harness matches the sensor plug.

Can anyone please have a look at their front o2 sensor and tell me what color from car harness matches with sensor plug.

Thank you and sorry once again.

Evo9_Dubai

a picture would be awesome

Evo9_Dubai

If someone can post a clear picture of the wiring like this it would be very helpful.
I can't make up which of the engine harness matches with sensor harness.

Ricoswave

iTrader: (5)

I am having it done today, if I get a chance I will get in there and snap some shots of the harness.

This has been such a pain to find a resolution for........sooooooooooooooo many dead end threads where people just abandon them and leave them hanging.

Evo9_Dubai

You are absolutely right... I found a thread that had the same question as mine, but no answer...

Anyway just please let me know know once you get that pic !!! I'd really appreciate it

Ricoswave

iTrader: (5)

So I tried getting it out today. Took the radiator out, put a nice size socket on it, and nothing. I had to abort mission out of fear of stripping threads on the o2 housing as I do not have a replacement and this is my dd. I will have to fight this battle another day, super frustrating. May order an o2 housing before I attempt this again.

Evo9_Dubai

Try to start the car for a little to heat up the o2 housing maybe that will help.

Evo9_Dubai

Can ANYONE please juste look at their Front o2 sensor car harness and confirm what color from car harness matches with sensor harness.

I've tried to search and can't find anything.

Ricoswave

iTrader: (5)

Sorry man I haven't been ignoring you, just mega busy. My cover is off my car, I can snap some pics tonight and text them to you worse case scenario.

On a side note I am now 100% sure that my trailing 02 sensor is outputting .80 or so at idle, and cruise conditions, which I am taking as the car running rich.

mrfred

iTrader: (50)

the front o2 sensor should be steadily bouncing back and forth across 0.5 V when cruising down the road at steady throttle. if it sits above or below, something is wrong. o2 sensors can be tough to remove. liquid wrench overnight is helpful.