M50 17mpg Help

[arthb7]

Ok a little update! I replaced the brake booster and the car seems to work smoother and brakes feel a LOT better. The gas mileage is still 17 mpg doesn't matter if city driving or highway. My new bosch 02 sensor should be here tomorrow so I hope it helps. The car still has a weird idle. When its cold it runs a little rough and seems to be very rich to a point where I can smell it inside. When its warming up it doesn't keep a straight idle. When its completely warned up it idles perfect.

[VintageBimmer]

I'm having the same problem (17 mpg). I'm currious to what you find

[arthb7]

A little update I found a vacuum leak. The valve cover gasket wasn't properly sealed. Replaced it and it made it better for about two days and now the idle is back to doing what it did before. I did find that if I unplug the TPS the idle straightens out so I ordered a new TPS and sent my fuel injectors to get rebuilt. Hope this helps.

[arthb7]

Another update! I replaced the tps and got a new 02 sensor also cleaned my fuel injectors ground! The car works smoother! It seems to work perfect when it's warned up! But this morning a new issue came up! If I turn my headlights on the car starts to misfire and I press the gas pedal and the rpms don't go up they stay around 1100! If I turn off the headlights its works normally! When the car warmed up I turn the headlights on and it was perfectly fine! Do I need another ground from the engine to the body?

[Nick_S]

Something is def not right. Normal highway cruising I can average 26-28mpg. My day to day driving with a good mix of highway, traffic and in town I still average 20-22.

What grounding points are you using? Did you add any extra ones? Did you splice the harness yourself or use an adapter?

[arthb7]

Something is def not right. Normal highway cruising I can average 26-28mpg. My day to day driving with a good mix of highway, traffic and in town I still average 20-22.

What grounding points are you using? Did you add any extra ones? Did you splice the harness yourself or use an adapter?

Well I have the main ground going from the engine arm to the body attacked on original e30 ground location! Then I have the injector ground on the top of the head! I don't think I have any other grounds! I have the e34 wiring harness! My wiring adapter was built for me by catuned! I'm thinking of adding another ground wire from the engine mount to the frame

[Nick_S]

What DME are you using?

[arthb7]

402

[Jib05]

alternator output at the right voltage?

[arthb7]

alternator output at the right voltage?

13.8v with headlight on/off

So it happened again this morning when it's cold I turn on low beans and the car starts to misfires! Only misfires when lowbeams are on! Anyone had this before?