TheChin

E39 540i 2001 from hell. Hesitation/Fuel Cut on Acceleration

25 posts in this topic

I really need help!

Last week; my car had a massive missfire fault and diagnosed as the MAF/AFM. This was changed with a replacement VW part; which subsequently didn't work. So swallowing that expensive pill; I bought the BMW Bosch replacement which has sorted that problem out.

Now... here comes the worst part of my entire week!

I finally get the car running normal; let it warm up like I usually do and accelerated.... and it hit a brick wall of NO power. It's fuel cutting and it's thrown a fault for fuel trim 1. Its happening on WOT but also seems to be lagging on half throttle; for normal driving.

Yesterday; it threw a dashboard fault for Transmission Failsafe Prog and now the gearbox seems "lazy" and is holding gears much longer than usual.

I've had the car for 6 months and it's driving like a bag of poo and i'm spending cash hand over fist; for it to continue to drive less poo; but still poo!

please; if anyone has any suggestions. I am at my whits end; I can replace any part and a good mechanic, I refuse to send the car in to find the fault only to find somethingh that can be changed by me. Expense is a problem at the moment. If it comes to that; then I will.

Thanks alot in advance, I hope your collective expertise can help out a fellow 5'er!

Share this post


Link to post
Share on other sites

its a good job they are sooooooooooooo nice to drive when all is well :?

cant advise other than read the codes again for clues.

strangley I got all those symptoms (misfire/lights on/all sorts) when the voltage dropped (alt problem)

Share this post


Link to post
Share on other sites

Is there a way to test the alt? I know they aren't cheap :(

(null)

Share this post


Link to post
Share on other sites

unlock the obc to get the hidden menu and see what the voltage is, also you can see the fuel usage in Litres Per Hour, if you get those figures it might be useful to see what is happening when the power cuts

we are breaking a e39 540i auto, so may have some spares if you need it, i can probably read if it has any fault codes aswell

Share this post


Link to post
Share on other sites

Fantastic I will do a search to unlock the obc. Someone did say that the alternator could cause the trans failure.

I will record all datas and update, will it continue to be in real time when driving! I may record it

(null)

Share this post


Link to post
Share on other sites

stolen from another thread

UNLOCK PROCEDURE:

1) Key to ignition pos 2 (no need to start engine).

2) Fasten the seat belt to get rid of the "Fasten Seat Belt" message.

3) Press the right button on the instrument panel, and hold it until "TEST-NR. 01" comes up (5 to 10 seconds).

4) Press the left button on the instrument panel, and the vehicle id comes up (last 7 digits of VIN).

5) Add up the last 5 digits to get the "unlock code", e.g. the unlock code for "AB12345" would be 15 (1+2+3+4+5).

6) Repeatedly press the right button until "TEST-NR. 19" appears.

7) Press left button -> "LOCK : ON"

8 ) Repeatedly press left button until "LOCK : xx" appears, where "xx" is your unlock code.

9. Press the right button. All modes are unlocked now.

NAVIGATING BETWEEN TESTS AND PERFORMING THEM:

- Follow steps 1) to 3) of the "UNLOCK PROCEDURE" to enter test mode.

- Use the right button to step from test to test.

- Press the left button to enter a test and cycle between modes within a test.

- Press and hold the right button to exit test mode (turning the key to 0 works as well).

Here is what I know about the various test modes:

2) Instrument test: Cute light show in the instrument panel. Ever wanted to see the speedo show 190 without having to leave the garage?

3) Don't know.

4) Current fuel consumption in liters per 100 kilometers and in liters per hour.

5) Average fuel consumption in liters per 100 kilometers and range.

6) Current fuel levels in left tank, right tank, and total.

7) Engine temperature (not sure where measured), engine RPM, and outside temperature.

8 ) Current speed in kilometers per hour.

9) Battery voltage.

10) Country.

11) Don't know.

12) Not sure what these are. Could be average speed used to calculate arrival time for distance to destination set in OBC?

13) Sound test. Goes through the various gong sounds.

14) Don't know. Could be some diagnostic codes.

15) DOn't know. Looks like a real-time readout of some registers.

16) Oil temperature. I sometimes get a bogus -48 degrees C when the engine is not running. Corrects itself when the engine is on.

17) Don't know.

18) Doesn't do anything.

19) Locking & unlocking of the test modes.

20) OBC Fuel Consumption Trimming. (Please see post #2)

21) Don't know. This test asks you "RESET?". Let me know what it does, if you're brave enough to try it. I'd recommend to stay clear, though.

Test 4 and option 2 immediately tells you how much fuel the DME is calling for. At WOT at redline in 3rd gear you should be aiming for this to show about 140 L/Hr. Anything much less signifies poor performance, with the main culprit being the condition of your MAFS, BUT this can show lower even with new or good MAFS, so then the search begins as to which sensor or other issue is letting the side down and putting the theoretical brakes on your car.

Test 7 will show you your true coolant temperature, and is not a reproduction of the signal being sent to your water temp guage in the instrument cluster. This should never really go below 79 Deg C once the car has warmed up. If so it is suggesting that your Thermostat is likely sticking in the open position, and your car is likely operating in warm up mode....very bad. This is best tested on a 60 mph cruise in top gear.....

Test 9 is a good way of seeing how healthy your battery is and also how good the charging circuit is too..

Edited by Mikey_535i
urquattro likes this

Share this post


Link to post
Share on other sites

Is there a way to test the alt? I know they aren't cheap :(

(null)

Tis just says to use a BMW tool.

Output should be at or over 14v at tickover. Mine (3 months old!) is pushing 13.4 and giving flat batt. 'Phoned the rebuilder today and he has put another on a courier for delivery tomorrow so I cant fault that as a service.

£250 from Alternatorman UK for the original exchange unit with 12 month warranty.

...and it didnt store any codes despite the missing etc but that may have been as I left it without a batt for 24 hrs ?

Edited by fatdaddy

Share this post


Link to post
Share on other sites

Ooh it sounds an expensive fault finding session. They can be rebuilt then?

(null)

Share this post


Link to post
Share on other sites

yes but I havent been able to locate parts to DIY

Share this post


Link to post
Share on other sites

My old mechanic rebuilds alternators for a living, may give him a bell

(null)

Share this post


Link to post
Share on other sites

easy enough to check the output you have to maybe eliminate the alt.........................

Share this post


Link to post
Share on other sites

The easier way of reading your alt output is to get a volt reader and put it on the bat. When the car is running with the lights on. About 14.4v is what you're looking for!

I had the 'holding back' or not revving past 2000 revs but it was down to almost running out of fuel! :rolleyes:

I've also had the same thing on my van! Yeah yeah ok not a BM but still it was the same fault and that turned out to be the fuel filter!

If your tank has fuel in it could be one of your fuel pumps!? Give uncle ray a PM about them also liddo had an issue with his pumps! ;)

Share this post


Link to post
Share on other sites

so we can select which bits of info to display on the dash panel via the stalk.................

can the choice of info be added to/taken away from the hidden nemu items?

Share this post


Link to post
Share on other sites

How many miles has the car done?

I would start simple, things like fuel filter, spark plug?

Check that voltage as these cars are really funny when there is a dead battery or bad alternator

Share this post


Link to post
Share on other sites

Well there has been some developments. It seems not to be the battery or the alternator, both have been checked and a constant 13.8v across both.

It is still hesitating (sounds like a missfire) at 3,500 - 4,000 RPM under WOT.

I've taken a video; this is on a WOT on a motorway, no lift off

Hope you can help

Share this post


Link to post
Share on other sites

I've not seen the vid but check your fuel filter and injectors!

Share this post


Link to post
Share on other sites

Just watched vid! Put some fuel in your car then try it! :rolleyes:

And when I say some I mean at least half a tank!

Edited by bigjay

Share this post


Link to post
Share on other sites

I filled it up after that point £105 and still.. the same!

Any way to do an injector test?

But surely it would affect it on normal driving, it only affects it on WOT.

Share this post


Link to post
Share on other sites

The first thing I would do is change your fuel filter! It's only about £20!

Then if it still persists I'd put some engine cleaner through it and run it through at least a full tank!

It could be your throttle position sensor? Or maff? Or you might have an air leak that is only detectable after 3000rpm??

Have you had the codes read??

Food for thought anyway!

And 13.8v is a little low TBH!

Share this post


Link to post
Share on other sites

I've put a new loan battery on. Maf is brand new, under 1 week!

I'll change the fuel filter this coming week

(null)

Share this post


Link to post
Share on other sites

Could it be a blocked cat? As its only high rpm/WOT

(null)

Share this post


Link to post
Share on other sites

To test for a blocked cat you need to get a basic pressure gauge and a lambda sensor bung and then remove the pre-cat lambda sensor on the cat you're testing and insert bung with pipe and gauge (when the car is fully warmed up) and then increase the revs to 3500 for 10 seconds monitoring the pressure - there should be zero to half PSI for a good cat, anything above that and it's likely to be plugged/blocked :)

Share this post


Link to post
Share on other sites

Fantastic ill get that sorted. I do hope that's the problem :(

(null)

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now