E36 328is Crazy high fuel consumption

[Johnboy Mac]

Don't want to be sending you off on a wild goose chase but an incorrectly operating autobox, even one with an intermittent fault could cause poor mpg. Do you know if the box is operating correctly?

[OptiManc]

Johnboy Mac said:

Don't want to be sending you off on a wild goose chase but an incorrectly operating autobox, even one with an intermittent fault could cause poor mpg. Do you know if the box is operating correctly?

No I don't, but I discussed this last night with my brother and dad and we had mixed opinions about it. However, my dad recommended I take it to a gearbox servicing station in Tameside so will give them a call on wednesday. However, I'm not holding my breath.

[Daniel1]

Have you changed the thermostat? I was reading somewhere that they stick open and don't let the car get up to temperature. The gauge is not a traditional gauge, rather just cold - ok - hot. Worth a check.

[E38Ross]

Daniel1 said:

Have you changed the thermostat? I was reading somewhere that they stick open and don't let the car get up to temperature. The gauge is not a traditional gauge, rather just cold - ok - hot. Worth a check.

Whilst its certainly worth a look, having had a thermostat stick open, allowing the car to reach about 25degs below normal temp the mpg was down, but not anywhere near that much.

[OptiManc]

E38Ross said:

Whilst its certainly worth a look, having had a thermostat stick open, allowing the car to reach about 25degs below normal temp the mpg was down, but not anywhere near that much.

Sorry for the late reply, I've been a little occupied and sort of getting used to a MK4 Golf I've recently bought till the E36 sorts itself out. Anyway, spoke to a couple of gear box servicing stations and they both said pretty much the same thing, if the gear box or torque converter were at fault I'd feel it and hear it and probably wouldn’t still be going nearly a year later. Never-the-less, taking her in tomorrow for a check anyway.

In terms of the thermostat sticking, wouldnt that cause a rough idle and perhaps even cause it overheat?

[E38Ross]

OptiManc said:

E38Ross said:

In terms of the thermostat sticking, wouldnt that cause a rough idle and perhaps even cause it overheat?

the electronic thermostats are designed such that if they do fail, they fail open....that's my understanding anyway. so basically, it'll run cold and not overheat. still not great but far less damaging than an overheat. mine wasn't running rough either, still silky smooth.....just like an M52 should be. but as said, it was still getting way better MPG than yours and didn't you say your coolant needle is running half way? mine wasn't (1/2 way is from 75 degrees upwards...hottest mine's run was 102 and was still bang on half way though!) ideal operating temp for the M52 is around the 93 degrees mark.

have you found what yours is running at yet? really easy to check.

[OptiManc]

E38Ross said:

the electronic thermostats are designed such that if they do fail, they fail open....that's my understanding anyway. so basically, it'll run cold and not overheat. still not great but far less damaging than an overheat. mine wasn't running rough either, still silky smooth.....just like an M52 should be. but as said, it was still getting way better MPG than yours and didn't you say your coolant needle is running half way? mine wasn't (1/2 way is from 75 degrees upwards...hottest mine's run was 102 and was still bang on half way though!) ideal operating temp for the M52 is around the 93 degrees mark.

have you found what yours is running at yet? really easy to check.

I submitted that post prematurely, i also wanted to add, i havent driven it for around 3 days, but drove it today for around 15 miles and I was getting between 18 and 22mpg, while the Range was ticking down as the miles climbed up, 1 mile for 1 mile or there abouts very closely. Then eventually it went back to behaving badly again.

@E38Ross thats very interesting, how do i find out what its running at? I know my OBC is locked, i assume i need to unlock it first?

[E38Ross]

i'm guessing it's the same for the E36 as it is the E38, as it's also pretty much the same on E92's as well

http://www.meeknet.co.uk/E38/OBC_Unlock.htm

i reckon it'll still be test 7, as said, it's still test 7 on the E92 M3.

[OptiManc]

E38Ross said:

i'm guessing it's the same for the E36 as it is the E38, as it's also pretty much the same on E92's as well

http://www.meeknet.co.uk/E38/OBC_Unlock.htm

i reckon it'll still be test 7, as said, it's still test 7 on the E92 M3.

Thanks E38Ross, I'm taking it again tomorrow, to go to the gear box garage so will run the process then and report back.

[tali1]

As someone with 20yrs worth of excessive Mpg from short journeys -i never found the cure.
What did the much hyped brim to brim show you? I'm not convinced any of the solutions offered are going to be cause of high Mpg.
Personally , it would be best to take it for a short motorway blast -a mixture of cruising and booting -that may be an easier option.

[OptiManc]

tali1 said:

As someone with 20yrs worth of excessive Mpg from short journeys -i never found the cure.
What did the much hyped brim to brim show you? I'm not convinced any of the solutions offered are going to be cause of high Mpg.
Personally , it would be best to take it for a short motorway blast -a mixture of cruising and booting -that may be an easier option.

The brim to brim made it clear there is a fault and its not computer malfunction. I've tried short blasts on the motorway and even dropped a gear to get the revs up.

Took it into the gear box guys today, they said the gear box and torque converter are in perfect working order, but changed the gear box oil anyway.

I am at an end.

[4rephill]

tali1 said:

As someone with 20yrs worth of excessive Mpg from short journeys -i never found the cure.
What did the much hyped brim to brim show you? I'm not convinced any of the solutions offered are going to be cause of high Mpg.
Personally , it would be best to take it for a short motorway blast -a mixture of cruising and booting -that may be an easier option.

Try reading the original post! (here's an edited highlight):

OptiManc said:

Anyway, problem is for the last 12 months or so I have been battling with its high, very high fuel consumption, it was never like this when I bought it in 2008.

This isn't a new car that's got a problem. the car has been owned for over 3 years and has suddenly developed the problem.

Going for "a short motorway blast -a mixture of cruising and booting", is not going to solve anything, the car has a problem.

The OP states he is getting @ 8mpg!. Unless he is only driving the car 500 yards down the road from cold everyday, he should be getting much more than 8mpg.

My drive to work in a 328i is @ 3miles and even on a freezing cold winter morning when the car is on the cold start cycle for the majority of the journey, I still get @17~22mpg.

If in 20 years of: "excessive Mpg from short journeys", you feel 8mpg is normal then I suggest you're either running a big block '70's yank tank or you haven't realised that your cars are seriously in need of help.

The OP has also reported:

OptiManc said:

Furthermore, performance is laboured from take-off and acceleration at any speeds; it takes ages to pick up revs, however! Occasionally it’s perfectly fine, quick, sounds smooth and prompt and fuel consumption stabilises. After a restart it'll go back to being lazy and gulping down the fuel.

That's not the sign of a car that merely requires an Italian tune-up down a motorway!

As for:

tali1 said:

I'm not convinced any of the solutions offered are going to be cause of high Mpg.

Any of the solutions offered could easily be the cause of the high mpg, all of the ideas suggested are well known for having excessively high mpg as one of their symptoms.

[4rephill]

OptiManc said:

The brim to brim made it clear there is a fault and its not computer malfunction. I've tried short blasts on the motorway and even dropped a gear to get the revs up.

Took it into the gear box guys today, they said the gear box and torque converter are in perfect working order, but changed the gear box oil anyway.

I am at an end.

Have you had the fault codes read?

The gearbox and torque converter may be mechanically fine but it could be an intermittent fault with the gearboxes electronic control system.

have a read here: http://www.bmwland.co.uk/forums/viewtopic.php?t=18...

I'm not saying this is definitely the cause of your issue but it's worth looking into a bit deeper.

[OptiManc]

E38Ross said:

the electronic thermostats are designed such that if they do fail, they fail open....that's my understanding anyway. so basically, it'll run cold and not overheat. still not great but far less damaging than an overheat. mine wasn't running rough either, still silky smooth.....just like an M52 should be. but as said, it was still getting way better MPG than yours and didn't you say your coolant needle is running half way? mine wasn't (1/2 way is from 75 degrees upwards...hottest mine's run was 102 and was still bang on half way though!) ideal operating temp for the M52 is around the 93 degrees mark.

have you found what yours is running at yet? really easy to check.

Right, I managed to unlock the OBC and get more information out about whats being consumed and results are as;
Consumption: 1.5 litres per hour, which I know is excessive, because my bro's V8 4.4/E39 is 1.5/per hour.

I wanted to get the temp as suggested but i wasn’t going to drive it at the time and haven’t since so i don’t have that for now, perhaps tomorrow.

Do you know what the fuel per hour should be around?
As far as I know the thermostat hasn’t failed but I suppose the temp will tell us eventually.

[Rollcage]

Poor performance and dreadful fuel consumption sound like MAF issues, but it's been changed you say. Was it for a genuine OE Maf, or an ebay jobbie?

Did you ever get round to changing the oxygen sensors? ( However, the normal emissions readings are a puzzle)

Is it possible that somehow the problem is road speed dependent, in that when stationary the car behaves itself? Something on the induction side maybe?

[OptiManc]

Rollcage said:

Poor performance and dreadful fuel consumption sound like MAF issues, but it's been changed you say. Was it for a genuine OE Maf, or an ebay jobbie?

Did you ever get round to changing the oxygen sensors? ( However, the normal emissions readings are a puzzle)

Is it possible that somehow the problem is road speed dependent, in that when stationary the car behaves itself? Something on the induction side maybe?

No it was defo an OEM from bmw specialist, BM Tec in Manchester, £265 if i recall correctly.

Haven't changed the O2 sensors yet because of the emissions being bang on and because they're so ruddy expensive if its not them i'd rather not open them - but having said that i've tried everything else so why not these too?!

Thats an interesting point, yes stationary its fine...its been stationery for nearly 30 mins sometimes and the needle hasnt moved, its been stationary and revved to kingdom come and no noticeable change in needle position, but on the move it starts to slide away. I've looked the induction manifold and from what I can see, stationary and engine off its fine, a bit of build up on dirt but not enough to cause alarm to an amateur like me. Is there a danger in having the engine fired up and not having the air induction manifold connected? I assume I’ll be by-passing the air filter and exposed to debris in the air?

[tali1]

Autoexpress magazine used to run a feature for readers cars with mystery faults (sorry can't find link) which AA/RAC usually fixed - perhaps give them a call?
Other than that you could go LPG?

[OptiManc]

lepetitoeuf said:

When I had my Honda ATR, my fuel consumption went from 30mpg down to 20mpg because of a slightly dodgy plug lead. Although there was a slight misfire under load which was noticeable it would run fine at normal speeds.

Thats interesting, my coil packs seem fine to my untrained eye, how did you go about tracking it down to one particular lead?

[OptiManc]

tali1 said:

Autoexpress magazine used to run a feature for readers cars with mystery faults (sorry can't find link) which AA/RAC usually fixed - perhaps give them a call?
Other than that you could go LPG?

LPG is an option however not one i want to consider, not until petrol reaches 200.9p per litre anyway (so next week then!) and it wouldnt solve the problem, except the problem would cost less!

The AutoExpress suggestion was recommended to me by someone else too, when I eventually got round to speaking to the right person, they told me the dont run that feature anymore. I should have just picked up a copy from WH Smiths in hindsight

[E30M3SE]

OptiManc said:

lepetitoeuf said:

When I had my Honda ATR, my fuel consumption went from 30mpg down to 20mpg because of a slightly dodgy plug lead. Although there was a slight misfire under load which was noticeable it would run fine at normal speeds.

Thats interesting, my coil packs seem fine to my untrained eye, how did you go about tracking it down to one particular lead?

If you haven't got a mis-fire it's not likely to be a coil issue.

Coils can be visually inspected for cracks, and tested by measuring the resistance between the outer 2 pins (there are 3 pins), should read somewhere between 0.4-0.8 Ohms.