m20b25 very bad fuel economy

[thomson1992]

Hello Guys ,

I need your help ,
I have a '89 e30 325i with 90k miles on it .
It have a very poor fuel economy , about 9 -10 mpg on town.
I' ve already check vacuum leaks , the tps sensor , temp sensor (about 300ohm after running) , O2 sensor , Afm , sparkplug , distributor , fuel pump , no leaking injector .
I've already done a compression test and everything's ok
Nothing change ; it still run like a pig .
Erratic idle , misfire below 2500rpm , low power

Can you help me

[dnguyen1963]

Erratic idle and misfire indicate big time vacuum leaks. How did you check for vacuum leaks? Smoke machine with plugged exhaust? Did you just check the O2 sensor or replace it?

[Kershaw]

You probably missed something.

Have you tried swapping in another DME?