Terrible Fuel Economy :S

[_ethrty-Andy_ 2132]

Okay so im getting really bad fuel economy. 200-250km to a tank. ECU can be ruled out as i have used three different ones and no improvement. I have disconnected the O2 sensor (unplugged) and that made no difference either. i thought maybe it was the TPS but ive been told that its is possibly a wide open throttle sensor and not a tps. my car was auto, is now manual. was bad before I converted it, i hardly use the car so i havent worried about it.

So that leaves the AFM which must be the problem? or does someone else have an idea i haven't thought of?

if i replace the AFM can i use one from any M20 or does it have to be from a B20?

ideally if someone has one of those code readers that would be great (have a separate thread on that already do draw attention to the fact i need one asap)

thanks guys (and girls)

[mitchE30 0]

it same problem of my old 325i,auto drain alot power.because it is old.I cant rev over 3000.so that I convert to manual.but it also bad,coz I drive wild.any way the code about your 320i last 3 digi is 092.325i 083.

[*Glenn* 854]

Does the car appear to be running properly ? No overfueling that you can visualy see ?

What is your diff ratio ?

[*Glenn* 854]

but it also bad,coz I drive wild.

Not really what we want to see on here or on our roads Mitch... Bad driving causes accidents

[_ethrty-Andy_ 2132]

Does the car appear to be running properly ? No overfueling that you can visualy see ?

What is your diff ratio ?

The car runs fine. nothing looks and sounds out of the ordinary. it is literally like someone syphons gas out of the tank.. there are no leaks anywhere etc (they dont syphon it.. the fuel cap is lockable)

Diff is currently 4.45 unlimited slip. twill be 3.6something Limited Slip next week though

[_ethrty-Andy_ 2132]

it same problem of my old 325i,auto drain alot power.because it is old.I cant rev over 3000.so that I convert to manual.but it also bad,coz I drive wild.any way the code about your 320i last 3 digi is 092.325i 083.

that sounds like a differnet problem. i can red line if i want to and there is never ever a loss of power etc. i have no idea what you mean by that code.. i need it read on one of those little gadgets

[*Glenn* 854]

that sounds like a differnet problem. i can red line if i want to and there is never ever a loss of power etc. i have no idea what you mean by that code.. i need it read on one of those little gadgets

There is very little to get out of a scanner on an E30. Gas analyser will tell you more about whats happening. Basicaly all you get from the scanner is engine temp & TPS position unlike the later model cars

[e30ftw 410]

Can be alot of other things, check condition of spark plugs (you can tell if the engine is running rich or what by the condition of them). Condition of the spark leads. Dirty injectors.

Driving style..

Could be alot of other things too..

[_ethrty-Andy_ 2132]

Can be alot of other things, check condition of spark plugs (you can tell if the engine is running rich or what by the condition of them). Condition of the spark leads. Dirty injectors.

Driving style..

Could be alot of other things too..

i do drive hard, but i went for a whole tank driving normally (that was hard haha) and got the 250km instead of 200. so yeah its still bad. spark plugs are newish, but what am i looking for on them to tell? i would think that it is running rich? spark plug leads appear to be fine. I ran some of that injector cleaner you can gett from Repcos and that made no difference

[_ethrty-Andy_ 2132]

There is very little to get out of a scanner on an E30. Gas analyser will tell you more about whats happening. Basicaly all you get from the scanner is engine temp & TPS position unlike the later model cars

Mine is a later model? or do you mean E36/46 etc?

[e30ftw 410]

It's e30's in general, they don't really throw any codes.. Just real basic functions.

I think having a high ratio diff from you car being auto doesn't really help. You will prob gain more mileage out of a tank going to something like a 3.64 or 3.73.

Does your car smell like it is running rich from the exhaust? Or spit out water / carbon deposits out the exhaust while it runs, or black smoke ?

[_ethrty-Andy_ 2132]

It's e30's in general, they don't really throw any codes.. Just real basic functions.

I think having a high ratio diff from you car being auto doesn't really help. You will prob gain more mileage out of a tank going to something like a 3.64 or 3.73.

Does your car smell like it is running rich from the exhaust? Or spit out water / carbon deposits out the exhaust while it runs, or black smoke ?

the car had this same fuel economy when it was auto. i dont see why BMW would make a car with such terrible economy. i wonder what other people with B20s are getting. I have no sence of smell so i cant tell you what it smells like, but no water or carbon comes out. nothing visable comes out except in winter time

[e30ftw 410]

My b20 was the same actually.. Worst fuel economy ever. But mine ran rich as, You could tell by putting your hand behind the exhaust it would spit out water with black carbon all over my hand. Indicating unburnt fuel.. Meaning it's running rich.

[Wervie67 0]

i wouldnt say that i was getting over 400kms. but im a student and drive like a nana (this also means i never have a full tank to test it )

Edited January 9, 2010 by Wervie67

[bravo 35]

It would help if you gave your economy numbers as litres per 100km, or at the very least how many litres and how many km.

There are different size tanks, so it'd be good to get some exact numbers for comparison.

[_ethrty-Andy_ 2132]

It would help if you gave your economy numbers as litres per 100km, or at the very least how many litres and how many km.

There are different size tanks, so it'd be good to get some exact numbers for comparison.

55L/200km = 25L/100km. my thing on the gauge cluster reads 6-8L/100km when im driving

[bravo 35]

Thanks. Is a fuel leak a possibility? It's hard to believe that the car will use that much fuel, yet appear to run normally.

[charles28 136]

My E30 320i Auto gets about 120kms per Tank, but thats due to the Odometer turning slowler than its meant to, its only recording about 1/3 of the actual KM's i'm driving, this isn't the 1st time i've seen an E30 with this fault either, some of them just stop altogether.

My E30 325i Manual gets 250 miles per tank, the odo on that is correct, as it hasn't been wound back like most Jap import E30's, its this that causes the fault i reckon.

[Wervie67 0]

sorry. 55L tank on mine

my gauge usually sits on around 8-9 L/100km aswell once its warmed up

Edited January 9, 2010 by Wervie67

[*Glenn* 854]

If it was using that much gas it would have driveability issues. The plugs would fowl, it would missfire under load, it would be hard starting and you'd definately black be smoking out the exhaust. Put it on a gas analyser and see what your getting first. Then get a locking fuel cap... might be your neighbour or flat mate

[Guest Simon*]

Jesus! Looking at your M20 mileages makes me glad I've got a V8! Waaaay more economical

[_ethrty-Andy_ 2132]

If it was using that much gas it would have driveability issues. The plugs would fowl, it would missfire under load, it would be hard starting and you'd definately black be smoking out the exhaust. Put it on a gas analyser and see what your getting first. Then get a locking fuel cap... might be your neighbour or flat mate

the clock has been wound back i know this. i have a spare gauge cluster so ill chuck that in and see. the trip meter seems to count the 100m intervals correctly so who knows. ill do a trip around the block (read hill) and then do it in the other car and see if i get the same distance. thats what i thought too. no gas leak that i can see anywhere, no drips when parked etc etc. fuel door locks on the central locking anyways, and why would they steal it from the bimmer when the one on my Lada doesnt lock at all haha

[bravo 35]

Check how many litres you actually put in next time you fill up. Unless you drive it until its actually spluttering before filling up, you won't have used all 55L if you have a 55L tank.

Make sure your odo is in km, not miles. As that would make it 13L/100km, not 22. (bsaed on an odo reading of 250, and 55L)

Check your odo. If you don't have an odo check site near you, get a mate with a newer car to drive the same distance as you. After 10km or so, check the mileages of both cars. (or use a GPS with trip function).

I doubt it's burning all that fuel, and it has to go somewhere.

[_ethrty-Andy_ 2132]

Check how many litres you actually put in next time you fill up. Unless you drive it until its actually spluttering before filling up, you won't have used all 55L if you have a 55L tank.

Make sure your odo is in km, not miles. As that would make it 13L/100km, not 22. (bsaed on an odo reading of 250, and 55L)

Check your odo. If you don't have an odo check site near you, get a mate with a newer car to drive the same distance as you. After 10km or so, check the mileages of both cars. (or use a GPS with trip function).

I doubt it's burning all that fuel, and it has to go somewhere.

No i fill it up and usually put 45-50L in. Odo is in kilometers, but the gauge face is miles (i know this because i put the miles face on because i think it looks better). i intend to do this trip.

[laadeelaa 0]

I hope you get sorted Andrew, that is just friggin nuts!