fuel trim

so i ran a scanner on my 1998 eclipse gst and it says the fuel trim is bad in both banks one AND two. i'm getting poor gas milage and when i push in the clutch (like coming to a stop) it will go from 3 grand all the way down to like 200 or 300 rpm then go back up to 1000 where it idles. some think its the ignition coils but they don't really no...i'm begging for anyones advice. thank you.

Are you talking about a P0170? I don't understand how you would be both bank 1 & 2, since we only have 1 bank. You find 2 banks in a V-6 or V-8, but never in a 4-cyl.

Anyway, a P0170 CEL is caused by the ECU's inability to compensate for what it perceives as a rich or lean condition. Using feedback from the O2 sensor (front) it determines if the previous combustion cycle was rich or lean. Based on that voltage feedback, the ECUadjusts the fuel trims to compensate and bring the mixture back to it's stoichometric point of 14.7:1. If I remember correctly the 2g's ECU is able to compensate up to + or - 17%. Once that limit is reached, the ECU throws the P0170 CEL. Keep in mind, this only applies at light cruise and idle....never at WOT.

Normally this is caused by a dead or dying O2 sensor. We can verify this using a logger. Do you have a logger, or have access to one? If so, set the logger up to display the front O2 sensor, STFT and LTFT. You will probably see that the O2 sensor is reading something like 0.04V and the STFT and LTFT will be maxed at +17%. The +17% value isn't set in stone, because I'm not 100% sure that is the maximum adjustment. Either way the FT's will be really high and most likely won't change.

Yes its die o2 sensor ( front ) I got the same code, and just change new o2 sensor, reset the ecu and the car ran alot smoth and no more code.