well if the ecu still sees it as working then how exactly could this be the problem of me losing power? sorry if this is sort of a noob question but i am still trying to understand why this could be the sensor

 

I obviously hate to say it's the O2 because it is so expensive.
I know that lead will kill an O2 reported pretty easily. I'd say if you've has it in the car like 10 times the thing is probably pretty contaminated. Al may be able to give you more information on the lifespan of an O2 with race gas.

You don't have a cat, right?

 

yeah i dont have a cat, i also have run race gas more than 10 times, also i would rather spend 250 on a sensor than have to rebuild parts of the head or anthing like that haha, also do you think that an o2 sensor can really do that much to my car to make it that much slower? and if it could what exactly is it doing to be able to make it that much slower, also thank you for your help with this i appreciate it

 

The O2 is working but it is not telling the ECU the true oxygen content of the exhaust.
As an example, the range is 0-1 volt. A normal working O2 will vary around .1 or .2 to .9 in closed loop., constantly changing back and forth. If it is contaminated it will often lose range and speed so it may only hit .3 to .8 and it will be slower. To the ecu this is still normal operation because it still reacts to fuel changes. Problem is, the car may be richer then .8 or leaner then .3 so the ecu doesn't know that, it ends up over compensating in either direction to keep the A/F where it wants it.

 

but wouldnt i have been able to tell when my car was on the dyno the other day? the a/f was being read by a sniffer in the exhaust

 

To be honest, if you've had race gas in the car that much I would say the performance of the O2 is at least degraded at this point. Whether it is the cure allfor the problem I can not say for sure but I would bet that it is not working as designed and is in fact affecting the car. Has your gas mileage changed much in the last month?

I know there are a couple threads out there about O2 changes due to race gas, we just need to find them and see how they knew or guessed to fix thier problem.

No problem, I used to be a tech and I hate a car with an unknown issue.

 

yeah i have been fighting this issue with my car for way too long and i am really getting fed up with it, i have been searching for the threads about bad o2 sensors and havent really come up on anything yet, other than the o2 do you have any other ideas because i can tell that you know what your talking about and could have some other ideas with this major power loss

 

No because you are reading the A/F via wideband and getting a number as a result. Narrowband O2 sensors like the factory ones have a very narrow operating range. The wideband is converting the voltage out put to an A/F ratio while the ECU looks at a narrowband for the actual voltage it is putting out.
I don't know the actual AFR a narrow is calibrated at but as an example let say it can read 1 point 12:1 to 13:1. As long as the ECU can make it cross the middle point 12.5:1 it considers it operational.

And if it is was is wrong you actually did see it on the wideband because you A/F is off. IF nothing changed the ideally the ECU is improperly fueling the engine based on what the O2 is telling it.

 

yeah i understand how i wouldnt be able to see if the o2 was bad on the dyno but what i was trying to say is that wouldnt i be able to see if my a/f was off on the dyno because it was using a wideband, like i said my car was running a bit rich but i leaned it a little so wouldnt that make my a/f fine and not even make the o2 sensor a problem?

 

i already have an upgraded fmic, sorry for not listing it, however the stocker can support 500whp, and i am not looking to upgrade the turbo to make up for the power i lost i am looking to find the problem to regain the power

 

that has been what i am thinking, my car is going in for a leakdown test next week, but for some reason i have the felling that i am pulling timing. but why would i be pulling timing? and would it effect me that much?

 

different dynos on different days, could be the reason you're seeing a difference. a 10% change in peak HP isn't that much. (you can see that difference from mustang to a dynojet) I believe motortrend did an article a couple of months ago where the same car on the same dyno the same day put down about 10hp different from one run to the next. Does the car acutally feel slower than it once did?

 

Do EVOs have O2 sensor test built into ECU? Every car I had, OBDII and OBDI, had built in O2 sensor tests. It would flash the check engine light for every time the sensor reads from lean to rich while you hold constant 2000k rpm and the service manual would have a range of exeptable results. If I remember correctly something like 10 cycles per 30sec being is a min. Not sure if EVO has something like this.

 

Honestly pulling timeing feels like your car hitting a wall. You can definetly feel the loss of power. Also temperature changes also cause the car to pull timing.

 

heh no hitting a wall feels like hitting a wall... or fuel cut!