High fuel consumption/ rough idle problems.

[ezzkazz]

Hi all,

I am pulling my hair out with my celica right now. The car is standard 04 plate, 53k miles, other than a powerflow back box which was on the car when I bought it. I had the car a good six months before I started having issues with the idle and its was maybe another 4 months after that before the fuel problem started to get worse. Over a period of a year or so Ive replaced many things to try and sort it out. 

The car is using a lot of fuel (its not a winter thing as this has been going on from before last summer), I probably get around half the miles of what it originally gave me. It backfires/pops on deceleration although not all the time and the idle is lumpy, sometimes really bad. When the choke is still on its even worse. The car other than that is responsive but idle is getting worse.

Ive changed the air filter, changed the plugs, throttle body taken off and cleaned, o2 sensors changed, maf sensor cleaned twice. Its just passed an mot and was told the car isnt running rich/lean (cant remember which one) and its been tested twice for leaks. No engine codes and no engine light is on.

Ive been to numerous garages to try to sort it but they either cant find whats wrong or they feel sorry for me and dont charge me because they dont want to spend a long time trying to find the fault. Im hoping someone may have had the same issue and can help me figure out whats wrong with it.