Hi so I engine swapped my automatic 03 lx and put in the d17a2 with the vtec. Also threw in the jdm 3 speed with overdrive automatic transmission. Car drives fine but the gas mileage is pretty bad I’m getting 8-13 mpg. I have no exhaust leaks or vacuum leaks. I don’t know how to fix that issue. The code I’m getting for my check engine light is “torque converter circuit open” but I replaced all the shift solenoids and it’s still there after erasing. I’ve been daily driving this car for almost a year with this issue and my only problem is my mpg. Someone said put an ex ecu in but I wanted to know will it be plug and play for what I have? I don’t have the wire for the vtec solenoid and egr so would I need an ecu and seperate ex harness?

 

The engine, transmission and ecu must all match in an automatic chassis. You cannot mix any of the 3.