z4 35i fuel consumption

[sachak]

lol I live in South Africa, I definitely don't have it set to miles, I would have a serious amount of speeding fines if that was the case.

With regards to injectors, I checked last night and they are definitely Revision 12 injectors...all of them. and as far as I recall I think they were replaced less than 10k km ago.

I have no miss fires
I had a bad 02 (Lambda sensor) a while back but I replaced that last year September with a brand new one and both are reading correct AFR values that being 14.7 while car is idling and making there way to +-12.5 under boost. I ran some logs yesterday to be sure of that.
Also on that note, before changing that bad o2 sensor, I used to get o2 sensor errors all the time on MHD and Carly which I no longer get since changing it out.

I can't see it as being bad coils or spark plugs at this time due to the car not having a missfire or rough idle.

What I do know is that when I did the oil filter housing gasket and I had to pull the intake manifold back I had a good look at my intake ports and the carbon build up was VERY VERY bad. However when the carbon build up is bad to the point of causing bad fuel consumption wouldn't it also cause a rough idle?

My brake calipers are perfect....I changed all 4 pads recently and replaced sensors and lubed those calipers up very well, they are functioning perfectly.

 

[R.E92]

lol I live in South Africa, I definitely don't have it set to miles, I would have a serious amount of speeding fines if that was the case.

With regards to injectors, I checked last night and they are definitely Revision 12 injectors...all of them. and as far as I recall I think they were replaced less than 10k km ago.

I have no miss fires
I had a bad 02 (Lambda sensor) a while back but I replaced that last year September with a brand new one and both are reading correct AFR values that being 14.7 while car is idling and making there way to +-12.5 under boost. I ran some logs yesterday to be sure of that.
Also on that note, before changing that bad o2 sensor, I used to get o2 sensor errors all the time on MHD and Carly which I no longer get since changing it out.

I can't see it as being bad coils or spark plugs at this time due to the car not having a missfire or rough idle.

What I do know is that when I did the oil filter housing gasket and I had to pull the intake manifold back I had a good look at my intake ports and the carbon build up was VERY VERY bad. However when the carbon build up is bad to the point of causing bad fuel consumption wouldn't it also cause a rough idle?

My brake calipers are perfect....I changed all 4 pads recently and replaced sensors and lubed those calipers up very well, they are functioning perfectly.

I'd get the carbon buildup sorted. Only cost me £300 in the UK. I wouldn't expect an extra 200km per tank but it will help performance.

What do your fuel trims look like in the logs? both long term and short term.

 

[sachak]

So the car is at the carbon doctor as we speak getting the carbon clean walnut blasting done, they are also going to run a bunch of diagnosis on the car and see if they can pick anything else up that might relate to the high fuel consumption.

Will show before and after pics of the carbon clean when I get them and let you guys know the outcome.

 

[willgill]

 

[sachak]

So got the car back yesterday afternoon after the carbon doctor and she definitely idles smoother and seems to be smoother and more responsive in general.

I will let the pics do the talking.

These are pics sent to me from the carbon doctor:



Before:








And then After:

 

[Smartbear]

certainly cleaned it up well think i'd get a catchcan plumbed in to stop that gloop making a reappearance :?
Rob

 

[sachak]

I have a catch can sitting in my garage that BMW decided to cut the pipes up or loose them.

However I have done allot of research and spoke to The Carbon doctor who told me he has done tests with the catch cans over extended time and found that it made little to no difference in the build up at all. After 40k km the build up was the same. :|

 

[1000rr]

Would a carbon clean be the same as terraclean?

 

[Kugaman1]

Nope, not at all.

Terraclean is definitely a cousin of snake oil! It cleans injectors but little more. It only works on manifold injection engines, not direct injection engines. Theres nothing that can clean direct injection engimes without some form of dissassembly.

Walnut blasting is a proven method thats really effective, just look at the pics!

 

[Gaffa22]

Terraclean, Ed China's snake oil

 

[HillWalker]

In my younger days it was known as having a decoke, a couple of hours whip the head off clean it up put it back together job done, if we wanted to get really racy we'd take it for a Crypton tune up then you were really flying, the good old days, and petrol 5 Bob a gallon. :wink:

 

[flybobbie]

I had carbon build on a aero engine.
The valve got jammed open, struck by piston, punctured the piston and very rough engine. Put the plane down in a field.
Very exciting for me and my trial flight passengers.

 

[Busterboo]

So the car is at the carbon doctor ... they are also going to run a bunch of diagnosis on the car and see if they can pick anything else up that might relate to the high fuel consumption ...

What did they say?

 

[sachak]

So the car is at the carbon doctor ... they are also going to run a bunch of diagnosis on the car and see if they can pick anything else up that might relate to the high fuel consumption ...

What did they say?

We ran diagnostics and nothing came up we ran real time logs while taking the car for a drive and couldn't pick anything up either.
However I do keep getting the error:

2CB8 - DME: Oxygen sensor after catalytic converter: Signal fixed at Rich.
2CB9 - DME: Oxygen sensor 2 after catalytic converter: Signal fixed at Rich.

My car has downpipes so I'm not sure if that's what is causing this? So in essence the car seems to be maybe running rich which could be causing this high fuel consumption?

 

[Busterboo]

Presumably, your first next step will be to see how much your fuel consumption has improved after the de-carbonisation.

 

[sachak]

so I spoke to a few people and found that because my car has no catalytic converters the o2 sensors after the cats which now sit on catless down pipes may be setting the mixture to rich which is causing the terrible fuel consumption.

So I just had catalytic converter foolers(mini cats) fitted to the car and hopefully this sorts the problem out. so far I haven't had the error come back. but the error is intermittent and usually only happens when I drive for a little while like on the motorway or something.

Will let you guys know what happens.

 

[dhobbs]

From what I've read, the coke build up is a result of oil seaping down from the valve stems and not the air intake. Seems to react with the metals of the engine.
This is only what I've read so please don't shoot me if you believe this is wrong.
As mentioned, fuel cleaner won't help and walnut blasting is the only option for now. But fuel cleaner may help with cleaning injectors and the exhaust sensors.

What's the milage required to do a walnut blast? Seems a service item now.

 

[sachak]

From what I've read, the coke build up is a result of oil seaping down from the valve stems and not the air intake. Seems to react with the metals of the engine.
This is only what I've read so please don't shoot me if you believe this is wrong.
As mentioned, fuel cleaner won't help and walnut blasting is the only option for now. But fuel cleaner may help with cleaning injectors and the exhaust sensors.

What's the milage required to do a walnut blast? Seems a service item now.

Na that's definitely not the reason for the build up at all.

Here is a better explanation for you to read up on the reasons and all the details regarding carbon build up on direct injection engines.

https://www.bmwfanatics.co.za/showthread.php?tid=38980

with regards to how often. they say every 40k km. but for me I will be doing it every year at least.

 

[Nanu]

ok so it sounds like something is definitely wrong with the car.

Could this be due to a bad carbon build up around the valves? would a wall nut blasting remedy this problem?

What other things on these cars would typically cause this kind of bad consumption?

Hi, the biggest influence on mpg is driving style-I only have the 20i but you can see what’s possible with the right technique...
AC20460B-DCD4-48F8-90DE-B69296F5D8F8.jpeg
Rob

Right technique??? I would be seriously worried about my driving technique if I was getting anywhere near the "average" MPG :evil:

 

[dhobbs]

From what I've read, the coke build up is a result of oil seaping down from the valve stems and not the air intake. Seems to react with the metals of the engine.
This is only what I've read so please don't shoot me if you believe this is wrong.
As mentioned, fuel cleaner won't help and walnut blasting is the only option for now. But fuel cleaner may help with cleaning injectors and the exhaust sensors.

What's the milage required to do a walnut blast? Seems a service item now.

Na that's definitely not the reason for the build up at all.

Here is a better explanation for you to read up on the reasons and all the details regarding carbon build up on direct injection engines.

https://www.bmwfanatics.co.za/showthread.php?tid=38980

with regards to how often. they say every 40k km. but for me I will be doing it every year at least.

http://www.oilem.com/turbo-fuel-stratified-injection-tfsi-direct-port-injection-carbon-build-up-problem/

Here's where I read about it. I'll read your link now. Thankfully my car is not affected by this, but useful to know for my next car.