Z4-forum.com

I have a BMW Z4 2.5 Litre 2004 (M54 Engine).

I was going along and it just cut out (Without Spluttering) as I slowed down and would not start for 10 mins.
Eventually it started and I drove back 10 miles - All fine.

Went out next day, got half a mile and same thing again - Got back to base OK.

On the drive it was still hard to start so I changed the Exhaust Cam Sensor (Because it's the only thing that has not yet been changed).

From then on it got worse, it was still hard to start, refused to idle and stalled if revved (Swapped back in old Ex Cam Sensor, then got another new one. No difference) or it just just stalls whatever you do and makes a noise at irregular intervals just like Small Stones being dropped onto glass (Coming from the Intake manifold area). The noise is at completely random intervals so I'm certain it's not a Pulley / Belt / Lifter etc.. (The Disa Valve could not make such a loud noise as it opens / closes).

Please see this Youtube link (Not my video) where someone else has a 2004 BMW E46 2.5 Litre (Same engine as mine) and has this problem.

You Tube Title - "2004 BMW 325i Engine Knock on Cold Start"

https://www.youtube.com/watch?v=WdqL8ou_S7g

The only difference is mine won't smoothly for long enough to warm up. It won't run for more then 30 seconds.


Before this happened my Z4 was running beautifully and I did the following before this problem arose -

Crank Sensor, Inlet Cam Sensor, Oil & Filter, Air Filter (Ok so not replaced) Maf Sensor (Used Item), Vanos solenoids cleaned & tested, Idle Control Valve Cleaned & tested, Injector cleaner added to tank a few weeks ago and some fed into the manifold while running, Throttle body replaced, Test & Clean Disa Valve, Vacuum / Smoke test, Serpentine Belt.


Since the problem started I've tried the following -

Exhaust Cam Sensor (Tried 3 of them), Left Battery terminal off overnight (Reset / Relearn), Upper Chains & Chain Guides visually inspected (Not loose or noisey). Servo vacuum line disconnected. Fuel Pressure tested (50psi at Shraeder Valve which stayed constant when running), Rear Oxygen sensors replaced, CCV Valve and hoses all replaced, Hydraulic Chain Tensioner renewed, x6 Coil Packs swapped to known good units, Fuses for Sensors checked (In White Plastic Box Under Bonnet), Check Spark Plugs are in tight. There's no Exhaust Leak or Blow. (MAF tried swapping back to old one and running with unplugged)


I've not yet done the following -

Compression Test, Remove/ Examine Spark Plugs, Test Oil Pressure, Test / Replace Knock Sensors, Test Replace Fuel Fump / Regulator / Filter, Front Oxygen Sensors, Remove & Test Injectors for leaks, voltage feed test for each sensor, Vanos Seals.

Is this random noise & stalling caused by some kind of misfire that you can only hear from the Intake Manifold?

There must be someone who has had this problem and know how to fix it....

What codes are you getting?

Yes I forgot to say- No Fault Codes At All.

As the engine stalls (Or just cuts out dead) it's only the EML light & Engine Block light that come - together with a single warning Beep sound.

I'm not sure if these warning lights & warning beep are related to these running issues - Or if these lights come on anyway as the the car is switched off..

MEV Z4 wrote: Sun Feb 11, 2024 11:26 pm Yes I forgot to say- No Fault Codes At All.

The fact that the EML light & Engine Block light become illuminated means that a fault code has been logged. Are you sure your code reader is working?

Yes my code reader is an Ancel FX5000, it's only 2-3 months old and is always kept in indoors it's original foam / box.

On the BMW Z4 it still reads a known fault code related to the faulty passenger occupancy sensor and a known fault with the Evap Purge Valve on my VW Golf 2.3 - So I'm sure it's working OK.

On the BMW Z4 the dashboard lights will only illuminate on stalling. Once you restart the car they go out - Until it stalls again.

I tried reading the codes at the point where the engine had stalled (With the lights still on), then tried after turning the ignition off and on again (Without restarting), then tried again with the car restarted and running.

No codes to be had....

FOLLOW UP - I found this video on Youtube where a BMW E46 experiences the EXACT same engine noise (Like Random Stones Being Dropped on Glass) while being driven hard.

Video Title - BMW E46 Oil Pump Failure

https://www.youtube.com/watch?v=wdWCxEe7etQ

The car in the video appears to still run OK and restart but the driver shuts it off to prevent further damage.

Although the driver does not follow up with any information about the repairs carried out later - he does write there that it's the Oil Pump that's failed.

Looking around on the internet it seems these engines are prone to the Oil Pump Sprocket nut coming off / plastic oil chain tensioner failing or the oil pump just chewing itself up.

Oil Pump failure fits with the car running badly as the Vanos may not be getting enough oil pressure to move the Cams to the correct position.

This would fit with no codes being given but it does not to fit with the fact that this noise is clearly coming from the manifold area - Not the oil pump / oil pump chain area.

Replacing the oil pump / chain / tensioner is a bit of a hassle as you need to support the engine with a brace and / or drop the subframe to get the sump off.

I'm reluctant to keep starting it in case it causes some permanent / fatal damage to the engine - So I'll keep on looking / asking for more advice on this issue before I start getting it apart.

Well, in the first video, a blocked PCV was mentioned. In the second, the oil pressure warning light was on for two minutes, warning the driver of a loss of oil pressure, so has your oil warning light come on? I do not trust that scanner, state your location and someone nearby may have a better one. I would also be looking at a blocked catalytic converter.

Yes I changed the PCV and all its hoses (Yesterday!) but it made zero difference. (Then I took apart the old PCV valve - It was all good inside).

The oil pressure light did not come on (Well spotted in the video) but that seems to sometimes be the case as the pump fails -

This video says the car gave no warning signs -

https://www.youtube.com/watch?v=_eq0TG1jZ0I

I'm in the UK in the TN27 postcode.

I realise there's been a time gap between the work you've done and the issues you've now got, but I can't help but think the issue is a result of one of the things you have changed.

If it's an oil pump then ultimately the knocking will in all likelihood be a rod bearing. a rod bearing would be a rhythmic knock, which would rise and fall in time with the engine rpms; it would not be intermittent/random. From the first video you linked to it seems like it's a random clatter.

Have you definitely used the right Cam Sensor?

Question - why on earth did you do all that work replacing sensors etc when the car was working fine? Especially choosing to replace with second hand sensors, just seems to be that you've invited problems?!

Have you pulled the DISA off to inspect the flap? You might find the motor is working but the flap has snapped and is clattering around in the inlet - which would also cause rough running, even if the DISA motor is meeting 'target angle'...?


I'd personally put money on it being DISA, Sensor or Vanos, in that order.

You say the noise is definitely coming from manifold area. The only moving parts in that area are fuel tank breather purge valve, ICV, throttle body and DISA. The video sounds like a flapping DISA to me

patriot66 wrote: Mon Feb 12, 2024 12:20 pmThe video sounds like a flapping DISA to me

Me too!! Least it's not an expensive fix... long as the flap hasn't broken and gone through the engine...!

Thanks for your replies.

Please check the info already given in the original post / request.

Ill clarify -

"Before this (Stone/Glass noise) happened my Z4 was running beautifully because prior to this issue (the Stone/Glass noise) the following were done (See original post for list.... Sensors / DISA, Idle Valve Cleaned tested etc).This was all done all 2-4 weeks before the (Stone/Glass noise) problem arose."

After all the sensors were replaced (With New Items) the car was running fine for a while .
The only used sensor was the MAF (Which I swapped in and out with the original and tried running unplugged to try to cure this Engine Noise).
(I cant see how my post can be misinterpreted that I put a load of Used sensors in).
Rear O2 sensors were replaced last week which was after the Stone / Glass engine noise problem began.

I think the DISA valve is good as it was removed and tested with this procedure, it holds a vacuum and is not loose in any way -

https://www.youtube.com/watch?v=so6xLmg1zno

Idle control valve is good as it hums and jumps to half open position with ignition on, it was thoroughly cleaned and rattles freely as you twist it .

I don't think either of them could make such a loud noise even if they tried.

DISA Noise -

https://www.youtube.com/watch?v=NRhDpADB87s

I'm reluctant to keep starting the car but I may yet take it off (And disconnect the Plug) then gaffer tape over the manifold hole. I dont know if it will start like that - but if the engine still makes this noise when the DISA is on the ground.....

Marbles in a tin can, possibly?

Classic description of M54 VANOS issues.

Prize for best answer goes to - SMORRIS_12.

I took apart the Vanos and the pistons in there were just flopping about in a puddle of really black oil - They're supposed to be a tight fit to hold oil pressure and move correctly.

Here's how to do it -

https://www.youtube.com/watch?v=0eUVF6OLFFg

After replacing the Vanos seals the strange irregular noise stopped and the car runs much better though still not perfect.

The conclusion is that this Stones / Glass OR Marbles in a Bucket noise is a misfire coming out of the intake manifold and it's caused by the cam timing being out because the Vanos isn't doing it's job.

The video I posted of someone with a car making the same noise (with failing oil pump) now makes sense - No oil pressure means Vanos does not work, cam shafts are out of time so he got the same misfire noise.

My car runs well now though with a poor idle and surging / revving itself / staying on high revs - I think this is the new Vanos seals bedding in as these problems have almost gone / corrected themselves.

Another problem has arisen - It cuts out when throttle is opened past halfway. I Suspect fuel pressure regulator? I'll open a new thread to see if anyone can help....

Hopefully you seem to have sorted the main problem. I was going to add my twopence that you should check the spark plugs since on my day car one of the the plugs internals had broken up and damaged the bore etc. made a similar noise, started but cut out in its death throes. Car went to the scrap merchant.
Plugs were purchased from ecp. I read somewhere that the market is flooded with copies and that ecp was implicated. For the reason I never use ecp now