X18XE1 engine or Z18XE?
Is the fuel trim showing a positive deviation?
Usually a faulty lambda or MAF sensor, or a massive leak on the intake or exhaust.
If it's the X18XE1 there is a problem with the earth from the MAF/IAT sensors to the ECU. You have to peel back the boot on the MAF plug, splice a new earth wire on to the existing yellow wire and earth it to the ECU housing.
Search for "x18xe1 maf earth mod" or "field remedy 2033" for more info.
If your mechanics are using decent diagnostic equipment they should be able to see if the MAF is sending an appropriate figure (about 11 to 14 kg/h at idle, though I believe TIS gives a range of 7 to 20 kg/h) and the lambda is switching correctly.
What town are these mechanics in?
limmy
May 2011
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.