Good day to you,
I just installed a AEM UEGO wideband yesterday on my ix. I put the sensor in front of the cat. towards back end of DP like suggested. Run the wires, and started the car...only the gauge reads 14.8 at start up and then continues to tack up to beyond lean readings until it reads three minus signs(---). it takes about 10 seconds for all this to happen at idle start up. It reads a constant --- until I rev and then it starts reading very lean until i get off gas it then comes back to lean with ---. I drive the car and watch the guage. At normal driving it bounces from 15+ to 17.9+. At WOT the guage swings all the back to extreme rich until i get off the gas and it drops back and reads --- lean.

Could this reading be due to a MAP o2 dump? It's been tuned. but, not since o2 dump and exhaust mani put on, but, i don't think thats a factor.

Thanks. Your help is much appreciated and greatly needed.

 

Who tuned the car the first time? And was the o2 dump the only modification you have added since the tune?

 

krazy house customs in NJ. no, the o2 dump and header were the mods done since the tune

 

Stock ECU?

 

Sounds like a wire got stretched or broken on the sensor possibly considering the tune is good. I had a similar isdue when a wire was stretched on my sensor but tg e dump isnt causing this.

 

is the sensor new or used?


if it is used make sure you using the calibrated bosch sensor from AEM. some people buy the new sensor from like auto zone and it’s not calibrated to work with aem UEGO gauge and through it way off.

http://www.aemelectronics.com/wideba...ent-sensor-635

also there could be an exhaust leak pre wideband sensor. usually from where the o2 dump bolts to the down pipe. are you running a 3 downpipe? is the doughnut gasket in there? is the doughnut gasket sealing correctly?

as soon as you turn the key but not start the gauge should read 15 and slowly got to full lean, that is the o2 sensor warming up. at idle your wide band for your evo and its tune should read 14.7 @ +or- .5 in either direction. the Stoichiometric Air Fuel Ratio for gasoline is 14.7 and that’s where you should be at normal driving ( no boost ) and at idle.

that information can be found here in the paragraph labeled "Specifically..." in the second paragraph second sentence.

 

bump, i am having the same issue as the OP, hey were you able to fix this issue and what did you do to fix it?

 

interesting, I hope the change isn't just from the install of the manifold and o2 dump

 

This can only be a few things. First off it could be an exhaust leak before the sensor. Check the sections of exhaust before the wideband all the way up to the exhaust manifold that you had installed. Make sure you check the gaskets for blowouts. Next it could be a boost leak. Check all your vacuum lines to see that they are nice and tight. If you don't have a way to test the leak (ie boost leak tester) use the soapy water method; it works. The last thing I would think is the sensor is busted. I really don't think that is the case. I'm leaning towards an exhaust leak. As soon as you car warms up and stops throttling on start up you slowly creep to full lean meaning there is too much fresh air getting in.