E36 328is Crazy high fuel consumption

[vsonix]

There's also a chap on m3cutters.net who sells diagnostic cable & software for about £30, I bought one but I got the E46 one by accident and haven't got round to testing it out on an E46 yet. However, everyone else who has one says it works for them and he's certainly very helpful when it comes to using it, there's a whole area of the forum dedicated.

[OptiManc]

Just thought I'd post an update. I haven’t had a chance to do much with the car yet due to work commitments.

However, my brother has been driving the car for a few weeks now and nothing has changed.

[4rephill]

OptiManc said:

4rephill said:

I still reckon the gearbox management system is going into "limp home mode" intermittently.

(And I know the gearbox itself has been checked out and found to be mechanically ok, but has the electrical management system been checked out?)

You're right the gear management system hasn’t been checked, would the 'limp' mode not display an orange cock symbol on the dash in this case? However, having spoken to mechanics and BMW veterans, their suggestions are that gear management system error would be detected by the diagnostics and changing gears wouldn’t be as smooth and seamless as they currently are...

Sorry I didn't reply to this post sooner!

My thinking is that if it's an intermittent fault, rather than a permanent one, then it might not be registering on the diagnostics.

Also, if it's an intermittent fault then the gearbox will work perfectly smoothly until the fault occurs and then it will simply stick in third and not change gear at all.

(BTW, the orange warning light on the dash for limp-home mode does work doesn't it? - not being funny, just trying to rule out anything obvious! )

This is one of the problems with modern cars, it's never as simple as you would think it should be!


I've recently had an issue with an intermittent fault with the traction control/abs system which didn't record a fault code at any time and every time BMW had the car, it never played up! All the wheel sensors gave the correct readings, the control module functioned correctly and every time they test drove it, it all operated correctly.

On a couple of occasions, as I was driving home from another failed visit, the lights on the dashboard came on so I turned round and went straight back to the Dealership. Guess what happened as I pulled into their car park? - the bloody lights on the dash went out!

I tried a replacement control module that I got from ebay, and for a couple of days it seemed to fix the issue. Then on the third day, the lights came on again.

In the end I told BMW to simply replace all the wheel sensors (I had little choice as the MOT was coming up! - isn't that always the way! ), and they found that although the rear sensors gave the correct reading and looked okay externally, one of them had corroded into the hub and was giving false readings that were never recorded on diagnostics.

They had to drill the old sensor out, clean up the hole in the hub and then fit a new sensor. Low and behold, problem solved! (and they didn't replace the other sensors as they were all in good condition! - they couldn't understand why the one rear sensor was so badly corroded though!).



I'm not guaranteeing that your issue is definitely a gearbox management issue, but your symptoms seem to match an intermittent limp home issue almost perfectly!

As always, best of luck with it, I really do hope you get it sorted!

[OptiManc]

Thanks for the reply nevertheless 4rephill. What car was this on? I see your point, the diag wont pick up the fault unless its occurring at that time.

I’ve experienced limp mode in my '92 E36 320 and its not that, in the 328 unless you know the car you dont know there is anything a miss but when the 'fault' shows itself the car is laboured, not massively but enough to know something is a miss. With limp mode its like its being forced to clean its bedroom or brush its teeth - it doesn’t want to do it!

the 320 has been scrapped now but i salvaged the transmission ecu so i'll swap them out and see what happens for a period of time but i suspect the issue will go undiagnosed.

[OptiManc]

Just wondering...could the fuel pump be at fault here? Supplying more fuel than required but enough of it is consumed and combusted not to alert the emissions testers, but excess fuel and not enough oxygen being supplied too its causing high consumption and low power output?!

[E30M3SE]

No. Fuel pump simply pumps fuel up to the injector rail, the injectors decide how much goes into the engine.

[seismic22]

OptiManc said:

Thanks for the reply nevertheless 4rephill. What car was this on? I see your point, the diag wont pick up the fault unless its occurring at that time.

I’ve experienced limp mode in my '92 E36 320 and its not that, in the 328 unless you know the car you dont know there is anything a miss but when the 'fault' shows itself the car is laboured, not massively but enough to know something is a miss. With limp mode its like its being forced to clean its bedroom or brush its teeth - it doesn’t want to do it!

the 320 has been scrapped now but i salvaged the transmission ecu so i'll swap them out and see what happens for a period of time but i suspect the issue will go undiagnosed.

The "laboured" like performance you describe is exactly like what im experiencing in my latest 323i. Ive just changed the CAT for another second hand item but that didnt work and shes showing no codes, has had a new crank sensor and the cam sensor is definitely ok. I managed to pick up a cheap CCV valve so im going to try that over the weekend and have a thorough look for air leaks.

[OptiManc]

seismic22 said:

The "laboured" like performance you describe is exactly like what im experiencing in my latest 323i. Ive just changed the CAT for another second hand item but that didnt work and shes showing no codes, has had a new crank sensor and the cam sensor is definitely ok. I managed to pick up a cheap CCV valve so im going to try that over the weekend and have a thorough look for air leaks.

Sorry you're having similar issues @seismic22, are you suffering with high fuel consumption too?

I havent consider the CCV valve, could you report back over the weekend with results?

[seismic22]

I will report back, I have Friday off work so will be tackling it then!

Yes Fuel consumption is very poor, I dont think as bad as you though, I cant get 300 miles out of a full tank but can get fairly close.

[OptiManc]

seismic22 said:

I will report back, I have Friday off work so will be tackling it then!

Yes Fuel consumption is very poor, I dont think as bad as you though, I cant get 300 miles out of a full tank but can get fairly close.

Cool thanks. I can get near 300, say around 245-265 on the motorway with no stops and smooth driving. But around town its shocking!

Looking forward to your results with bated breath!

[seismic22]

Im sorry to say that its made no difference.

I changed the CCV valve and cleaned the breather pipe and the ccv to dipstick pipe out.

My next thing to look at is the brake booster non return valve coming out the manifold. I was driving rather fast late at night on the motorway the other day and after a prolonged period like this performance suddenly picked up briefly and with it the brake pedal became firmer. It soon went again though so for the sake of a second hand one down the scrappy I'm going to give it a go. Also going to change the gearbox oil and fuel filter but I cant imagine its either one of these

Oh..also i'm currently seeing 23mpg average (worked out from brim to brim test), I know this could be worse but it could also be alot better!

Edited by seismic22 on Saturday 15th December 10:15

[ian_touring]

Hope you manage to fix this, OP. When my 323 touring thermostat failed in the open position, I was getting 17mpg around town. Depressing, paying the price of, say, M3 performance, without any of the benefits.

[OptiManc]

seismic22 said:

Im sorry to say that its made no difference.

I changed the CCV valve and cleaned the breather pipe and the ccv to dipstick pipe out.

My next thing to look at is the brake booster non return valve coming out the manifold. I was driving rather fast late at night on the motorway the other day and after a prolonged period like this performance suddenly picked up briefly and with it the brake pedal became firmer. It soon went again though so for the sake of a second hand one down the scrappy I'm going to give it a go. Also going to change the gearbox oil and fuel filter but I cant imagine its either one of these

Oh..also i'm currently seeing 23mpg average (worked out from brim to brim test), I know this could be worse but it could also be alot better!

Edited by seismic22 on Saturday 15th December 10:15

Thanks for the update seismic22, sorry it didnt work for you. Thats an interesting suggestion with the breaks; i'm sure my breaks have been checked and OK'd. But I've had the same experience as you, suddenly performance improves for a moment, its prompt, sharp and effortless then goes back to laboured and thirsty.

I've been seriously considering changing the Transmission ECU; I have one from my old '92 E36 320i, if the part numbers are the same i'll swap them out else find another. I have been advised here to have the ECU checked but I cant anyone who is willing to do it or think its worth doing.

Please keep us posted on your results!

[OptiManc]

ian_touring said:

Hope you manage to fix this, OP. When my 323 touring thermostat failed in the open position, I was getting 17mpg around town. Depressing, paying the price of, say, M3 performance, without any of the benefits.

Thanks! Tell me about it!

[bussinessacc]

Hi , did youmanage to find the problem with the fuel consumption ? i have the same problem . my car 323ti start to go for 15l/100 city and before was arond 13.5 .

Do you have checked the brakes calipers , happent to me before to have a blocked caliper and the fuel economy was verry bad . Did you have checked the fuel presure regulator vacum ?

did you identify the problem ?


thanks

[OptiManc]

Hi
Unfortunately no, its still the same - sorry you're experiencing the same problems.

I haven't checked the fuel pressure no, its going in for a service at some point I'll remember to get them to check it. In the hot weather mine seems to get worse and it has been overheating, I think the wax coupling is worn, so perhaps that's a cause of my poor fuel consumption. Worth checking on yours?

[retro_racer]

I HAD the same problem. But this is a long thread, so I'll just say, it's you inlet cam sensor...! (and wait for the" I've changed it" reply)...

I had a e39 2.8 - felt like a dog. then an E39 2.5, felt amazing. Then got an e46 2.8, felt like a dog.... So swapped the inlet cam sensor, and after a hiccup and some resets, the car feels supercharged. I think theses sensors really suffer from heat damage - and it may be just coincidence, but the cooler weather and me pulling all the sound proofing out of the bonnet seems to have stopped the new sensor failing...

[OptiManc]

...and here it is. Yep, already changed it, in fact I think it was one of the first things I changed myself after the multiple workshop visits.

[Rollcage]

As I posted about a year ago, it need proper diagnostic evaluation. With all the will in the world, randomly changing components because some chaps off the internet said so won't do you any favours. Performed by a competent operator, it's worthwhile doing, and will save you money.

[OptiManc]

Rollcage said:

As I posted about a year ago, it need proper diagnostic evaluation. With all the will in the world, randomly changing components because some chaps off the internet said so won't do you any favours. Performed by a competent operator, it's worthwhile doing, and will save you money.

I have had it diagnosed 3 times from two places, one being BM Tech in Manchester and another a mobile diagnostic guy. At the first scan it was the MAF, changed that but no change improvement in drive/consumption. After that no reported errors, even risked a ROM flash. I am always told though such and such..."don't always show up on the scanner"