2.2 swapped into 2.5 need help

[jheidelmark]

Ok so heres the jist. I blew my motor from my 98 2.5 gt about 3 months ago and got a ahold of a 2.2 w/ 40000 miles on for cheap so i put it in. I put the 2.5 flywheel and clutch in, and swapped the ecu to a 2.2(even though it ran with a 2.5 ecu). put new wires and plugs in and ran cleaner through it. it runs strong, but I have a problem. I'm averaging 18-20 mpg. i also have uel headers on it, but it made no difference in gas mileage. Im trying to figure out why im not getting the proper mileage for a 2.2?? Can it be that I still have my 2.5 fuel pump? or doesn't that matter?

[jey]

How old are you O2 sensors? You could have a lazy O2 sensor...

[jheidelmark]

i have brand new second one. and idk about the front. but i was getting better mpg with my 25 with the same sensors

[jheidelmark]

anyone?????

[dubkeith]

I swapped a 2.2 into a phase 2 2.5 and just used the 2.5 ecu, wiring etc. My car ran no less than 28-30 mpg. Deffenitely check for fuel leaks. Doesnt make sense.