Excessive fuel consumption

[Bumpa]

I've been reading about cleaning the throttle body recently. Apparently they get pretty mucky and that can cause poor running and consumption. Some of the Youtube mechanics reckon it should be a regular service job, say with every major service. I bet mine has never been done.

 

[roadvoyager1]

As @colb mentioned, check for air leaks. Keeping it simple, there are 2 short ducts ( about 3" diameter) between the air filter box and the inlet manifold. The second one has a small breather pipe on the underside. Check this carefully for splits if there are none in the main ducts. Replacements cost £10-12 each from BMW a couple of years ago.
If these rubber parts are okay then investigate further using the code reader.

 

[the Nefyn cat]

There's a couple of rubber caps on the back end of the inlet manifold that can perish and split, parts 15 & 17 on here https://www.realoem.com/bmw/enUS/showparts?id=CN12-EUR-01-2002-Z3-BMW-Z3_22i&diagId=11_6239 , worth having a look round there, too.

 

[gookah]

Stu has been around mine with the car today, and I took a look.
INPA showed no faults, and all cylinders running smooth, and equal.

Inlet hose fine, Had been changed a couple of years ago,
There was one thing I saw though, which made me think back to a time I did this for someone else at a show .
The reports back I had after that one, I thought at the time, surely could not have made such a difference..

I did the same again, Stuart called me back after he went on a 70 mile drive, just to let me know the results.

I will let him post his findings, if his results stay the same, my suspicions may be correct......

 

[handsomejackuk]

@Lonestar ?


we waiting....

ahem well i wouldnt mind knowing... if what Pete did worked..

 

[Lonestar]

Sorry guys (and gals!), started a new job yesterday so a bit hectic!

Pete reset the service indicator. No faults were showing......

I really dont want to add to the myth but my god, shes quicker off the mark, seems lighter on the steering and a LOT better on fuel.

Its like Betty is a different car... !

Cheers Pete

EDIT: Although shes been serviced, I havent reset the indicator. Whilst I admit that shes not perfect, she is well looked after and suffers looks wise. Quite impressed with Petes computer results though. Shes running pretty well for a 22 year old motor!

 

[gookah]

I had heard that as the service indicator counts down, it also reduces performance and increases fuel consumption.
That way when you pay £££££'s for a service, everything was actually better afterwards, so people actually 'felt the difference an oil change makes! ' and therefore more likely to pay BMW for it again and again..

This is the second time now I have done this where I have had reported back a night and day difference, just from doing this alone.....

Now a car manufacturer would not be so cynical as to make software do something it shouldn't, would they?

 

[Lonestar]

I wouldn't have believed it if it were someone else on here as I'm sure others wont but the difference is astounding....its just so much of a change that it can't be psychological.....

 

[handsomejackuk]

It's another thing I need to do.... Well worth trying I let you all know if it makes any difference.. the thermostat has made a big difference in warm up times now on middle of guage in under 2 miles.. I may just try replacing the vicous fan

 

[handsomejackuk]

Thanks for the feedback and sharing this with us

 

[Dino D]

I had heard that as the service indicator counts down, it also reduces performance and increases fuel consumption.
That way when you pay £££££'s for a service, everything was actually better afterwards, so people actually 'felt the difference an oil change makes! ' and therefore more likely to pay BMW for it again and again..

This is the second time now I have done this where I have had reported back a night and day difference, just from doing this alone.....

Now a car manufacturer would not be so cynical as to make software do something it shouldn't, would they?

I have always noticed the difference after a ‘service’ even though my car gets an oil change annually l, so sometimes as little as 3-4K miles on the oil...

I’ve only about 3k this year but the service lights are down to the last one and it feeling quite grumpy especially when cold.
Will have to give the service light a reset and see!

Didn’t think our cars would be clever enough to be able to do this...can only imagine the stuff they can get up to with newer cars...what next Tesla batteries dying off really quickly after a new model is released (ala Apple?!)

 

[colb]

Mike Fishwixcks explanation will confirm your suspicions about degraded performance as the service and inspection timer counts down.
https://zroadster.org/articles/bmw-z3-resetting-the-service-indicator-by-mike-fishwick.72/

Interesting point he makes is that if the cap is removed fromthe diagnostic socket it puts the car into service mode, if you have lost the cap it might be a good idea to replace it.

 

[the Nefyn cat]

Well, the Z is off the road at the moment, so I've just been out and reset the e46s service indicator and the fuel consumption bit of the OBC. Be interesting to see if it makes any difference. If it does then I'm sure it's just a case of BMW being caring about our engines, and not just some cynical ploy to get people into their garages. Oh no.

 

[handsomejackuk]

Mike Fishwixcks explanation will confirm your suspicions about degraded performance as the service and inspection timer counts down.
https://zroadster.org/articles/bmw-z3-resetting-the-service-indicator-by-mike-fishwick.72/

Interesting point he makes is that if the cap is removed fromthe diagnostic socket it puts the car into service mode, if you have lost the cap it might be a good idea to replace it.

Service cap is always left off in my 1.9.... as I run and obd adaptor In There

 

[gookah]

@Devon Z

why did you disagree with my previous post about PM's?

 

[e36Ballen]

possible suspects:

-cam and crank sensors
-fuel filter
-some vacuum leak

 

[ktnez99]

I've been reading about cleaning the throttle body recently. Apparently they get pretty mucky and that can cause poor running and consumption. Some of the Youtube mechanics reckon it should be a regular service job, say with every major service. I bet mine has never been done.

Blimey! What the heck is the throttle body?!?

 

[ktnez99]

Interesting read everyone. Worthy points raised and addressed. Thanks for sharing your experiences. It all helps us novice mechanics to grasp what’s happening with our cars.

 

[the Nefyn cat]

Blimey! What the heck is the throttle body?!?

The bit that lets the air into the engine, opened and shut by your right foot. Simples.

 

[eminem94]

My 1999 Z3 1.9L took me 320 miles on a single tank, not sure if that's good or not but I didn't speed whatsoever so that's probably why