Fuel Trim Check Engine Light.. whats wrong?

[BoostInsideTSi]

I have had my check engine light on for quite a while, ever since I hooked up my new exhaust with test pipe, so I figured it was just the 2nd o2 sensor giving off a bad signal. I went to the chicago meet yesterday and had someone with a pocketlooger hook me up, and he found 2 problems for the check engine light.
1. fuel trim problem
2. something to do with the idle.

anyway, from what I can remember here, does anyone know what would be causing these problems or what would fix them? Thanks,
Mike

PS. We were having a hard time picking up o2 volts, it was reading like a .01, something like that (only tested at idle). could this be from a bad o2 sensor? I would be able to change my o2 sensor from my test pipe and put it into my o2 housing right?

 

[psychlow]

Yes, it could definitely be the O2 sensor.

The ECU adjusts fuel trims based on oxygen sensor data. If the O2 sensor is fugged, it'll keep trying to adjust until it no longer has any room to go (meaning the fuel trim gets maxed). If it still reads bad O2 readings after that, it'll trip the fuel trim CEL.

I don't think you can move the rear O2 sensor up - I believe they're different types of sensors. The front O2 sensor is heated, the rear isn't (IIRC).

 

[DSMeclipse4G63]

only the front o2 can cause fuel trim problems, the rear is only for the ctalyst monitor. The front will cause fuel trim codes like malfunction and tacking too long to go into open loop. Driveability will occur from front o2 sensor problems but not rear, and yes rear o2s are heated for emissions sake.
Andrew

 

[Coldandafraid]

did you hack your mas or anything? you say you O2 readings are too low, thats why you have the fuel trim error.

 

[mazdamx6pwr.com]

I'd deffintly replace your front 02. They usually read low/lean when they start to fail. If your getting .01 its totaly crap.

 

[BoostInsideTSi]

yes i did hack my mas. took out all 4 honeycombs, (yes i know, bad) and I assume you are right, that this would be causing my fuel trim problem. Can this be slowing me down or causing timing to be pulled? Thanks,
Mike

 

[Coldandafraid]

it is causing you to have a very lean idle, and a fairly lean WOT. I just finished putting a friends honeycombs back in, and it corrected the same CEL, and the car runs much smoother now.

 

[mazdamx6pwr.com]

If you getting low readings on the O2 you still need to fix that as well.

 

[Coldandafraid]

yes.... but he is (most likely) getting the low O2 readings because of the hacked mas.

 

[Syndicate13]

Screw hacking a MAS to make the car run the way you want. Do it right and buy a fuel computer, I'm pretty sure Mistu engineers spent at least a few hours designing that MAS and put the honeycombs there for a reason.

 

[BoostInsideTSi]

I did buy a walbro 255, 550cc's, and an safc, after removing the honeycombs. however -- Stupid me thought it would be cool to "crush" the honeycombs, and now, if I want to replace them, I need to buy a whole new MAS. (80-100 on dsmtrader.com). Is the fuel trim error code pulling my timing or anything like that?

 

[temfate]

A used MAS is normally only about $25 at a scrap yard...