I've been running around trying to fix the mileage on my e30 m20 since I bought the car a few months ago. Nothing has seemed to help at all until now.
I replaced or checked the following with no effect:
plugs
o2 Sensor
known good AFM
fuel pressure regulator
injectors
cap/rotor
air/fuel filters
thermostat (was actually broken open...car ran cold for a couple months)
intake boot
ICV
sprayed engine with carb cleaner to check for major vacuum leaks
checked fuel return line for flow
Nothing made the MPG budge from about 18 combined, and it didn't matter whether I hooned it or drove like a grandmother.
Today I tracked it down to the crankcase vent tube, aka bitch tube. A previous owner (or their mechanic) had left the spring bound up with steel wire, allowing the tube to sit loose. The top seal was visibly poking out of its seat in the intake manifold, creating a vacuum leak. I removed the wire, let the tube re-seat, and I seem to be getting reasonable mileage now.
I was at about 23 hwy/13 city, I'm now around 30 hwy/23 city.
In L/100km.That's 11hwy/17city before, 8hwy/10city after.
City MPG will probably go way down on my rush hour commute, but that's worlds better than what I was getting. The exhaust is noticeably odorless now.
I replaced or checked the following with no effect:
plugs
o2 Sensor
known good AFM
fuel pressure regulator
injectors
cap/rotor
air/fuel filters
thermostat (was actually broken open...car ran cold for a couple months)
intake boot
ICV
sprayed engine with carb cleaner to check for major vacuum leaks
checked fuel return line for flow
Nothing made the MPG budge from about 18 combined, and it didn't matter whether I hooned it or drove like a grandmother.
Today I tracked it down to the crankcase vent tube, aka bitch tube. A previous owner (or their mechanic) had left the spring bound up with steel wire, allowing the tube to sit loose. The top seal was visibly poking out of its seat in the intake manifold, creating a vacuum leak. I removed the wire, let the tube re-seat, and I seem to be getting reasonable mileage now.
I was at about 23 hwy/13 city, I'm now around 30 hwy/23 city.
In L/100km.That's 11hwy/17city before, 8hwy/10city after.
City MPG will probably go way down on my rush hour commute, but that's worlds better than what I was getting. The exhaust is noticeably odorless now.