m42b18 high gas mileage

[sjoerd]

hey,
my e30 318is uses 13l/100km when i'm drivin as economical as i can and and a lot of people who alsow have 318is's say they can get 8-9l/100 when driving economical and there is somthing wrong with mine but i do not know what could be wrong.. engine still  drives verry smooth
someone anny idees where i can start searching?

grtz sjoerd

[Slowered318]

What grade of gas do you use? Ethanol doesn't work well in these older cars.

13l/100km sounds a bit high but if it's running well I wouldn't start messing around. Check for air leaks and run an emissions test, that's a good start for diagnostic. Also try and borrow an infrared thermometer, top up your tires to 34psi and take it for a drive down the highway at night, pull over to check the brake disks. Often a seized caliper or parking brake can drag you down.

I'm getting about 9 highway 11 city with a chip, mustang injectors and Shell 91 octane. Practically zero emissions but the gearing and narrow power band really kill the mileage. I bet with a 3.46 gear, EcoPlus tires and fresh synthetic fluids I could compete with a Prius for highway mileage. lol

[sjoerd]

What grade of gas do you use? Ethanol doesn't work well in these older cars.

13l/100km sounds a bit high but if it's running well I wouldn't start messing around. Check for air leaks and run an emissions test, that's a good start for diagnostic. Also try and borrow an infrared thermometer, top up your tires to 34psi and take it for a drive down the highway at night, pull over to check the brake disks. Often a seized caliper or parking brake can drag you down.

I'm getting about 9 highway 11 city with a chip, mustang injectors and Shell 91 octane. Practically zero emissions but the gearing and narrow power band really kill the mileage. I bet with a 3.46 gear, EcoPlus tires and fresh synthetic fluids I could compete with a Prius for highway mileage. lol

thanks for the quick reply
i use 98octane,the brake's are good, i changed all of the vacuum hoses and changed all the filters. could it be a problem with the O2 sensor or mass air flow meter?

[Slowered318]

I would throw in a new O2 sensor, it's likely messed up if your cars been running rich for a long time. Emissions specialist should be able to pinpoint the reason your fuel consumption is so high. Should be a writeup here on testing your VAF sensor, it can be taken apart to clean the contacts and make adjustments but I would acquire a spare one if you're going to try this. I would also back down to 90-95 octane, a normally aspirated 10.5:1 compression engine really doesn't need it IMO.

[DesktopDave]

sjoerd, I'm guessing you're in the EU? Your M42 may not even have an O2 sensor.

I'd consider investing in a wideband O2 sensor, like the Innovate Motorsports unit. Run it stand-alone to determine your car's fueling issue. They're not that much more expensive than the OEM BMW unit, and they're made by Bosch. You can find the sensors in salvage yards in VWs built around 2000, but you'd still need a controller to interface it into the car.

BMWMan91 has a thread here somewhere about installing one in a US car.

[sjoerd]

sjoerd, I'm guessing you're in the EU? Your M42 may not even have an O2 sensor.

I'd consider investing in a wideband O2 sensor, like the Innovate Motorsports unit. Run it stand-alone to determine your car's fueling issue. They're not that much more expensive than the OEM BMW unit, and they're made by Bosch. You can find the sensors in salvage yards in VWs built around 2000, but you'd still need a controller to interface it into the car.

BMWMan91 has a thread here somewhere about installing one in a US car.

yes i'm from the EU but i have a O2 sensor, i gonna try with a new O2 sensor cause my car had that hot starting proplem for more than a year (until i found how to fix it on this forum )and the 1st minuts it was always running to rich and i think that messed up the O2 sensor

[e3091318is]

What grade of gas do you use? Ethanol doesn't work well in these older cars.

13l/100km sounds a bit high but if it's running well I wouldn't start messing around. Check for air leaks and run an emissions test, that's a good start for diagnostic. Also try and borrow an infrared thermometer, top up your tires to 34psi and take it for a drive down the highway at night, pull over to check the brake disks. Often a seized caliper or parking brake can drag you down.

I'm getting about 9 highway 11 city with a chip, mustang injectors and Shell 91 octane. Practically zero emissions but the gearing and narrow power band really kill the mileage. I bet with a 3.46 gear, EcoPlus tires and fresh synthetic fluids I could compete with a Prius for highway mileage. lol

I never really thought of brakes dragging to be honest.  I should probably have my rears checked out.  I do hear some constant noises at higher speeds coming from the back.   Also, when the car is jacked up and I spin my front tire you can hear what sounds like brake pads hitting the rotors.

[sjoerd]

I would throw in a new O2 sensor, it's likely messed up if your cars been running rich for a long time. Emissions specialist should be able to pinpoint the reason your fuel consumption is so high. Should be a writeup here on testing your VAF sensor, it can be taken apart to clean the contacts and make adjustments but I would acquire a spare one if you're going to try this. I would also back down to 90-95 octane, a normally aspirated 10.5:1 compression engine really doesn't need it IMO.

in belgium we can only get 95 of 98 and evreone says the engine stay cleaner (is bether) with 98octane

[Slowered318]

in belgium we can only get 95 of 98 and evreone says the engine stay cleaner (is bether) with 98octane

Sorry, I was not aware you were in western Europe. If I'm not mistaken 98 (RON) octane here in NA is 93 or "Premium", 98 (AKI) would be specific to racing fuel.

[e3091318is]

I get an average of 28 mpg (maybe 80% highway and 20% city) on my regular use.  I recently took a drive to vegas going up and down hills, change in speeds, and some quick runs and got a solid 30mpg mostly going 75-85mph (80 was my cruise speed).  I have a rebuilt engine with a 3.73 LSD so my highway RPMS are nice.  I could probably squeeze 1-2mpg if I cleaned/replaced injectors, better tires, fixed 1222 code, removed the 150lbs of shit in the back, fixed rear wheel bearings, and shifted a bit better.