N52 hesitation, stuttering, jerking, surging etc

So I've noticed something weird and seemingly fuel pump related. I have heard this noise before but for some reason I thought it was the neighbour out with their electric lawnmower or something. The best way to describe it is like the fuel pump is 'revving' randomly and seemingly in time with when the idle RPM fluctuates. It seemed to make this 'revving' noise after a cold start and then settle when the revs get to normal idle (660rpm), during which time the fuel pump seems to sound 'normal' but I think I can still pick out irregularities in the sound it emits.

Now, I am not sure whether this is normal or not so I am hoping I can have some input on this. I have uploaded a video in which the pump makes this noise once or twice, prior to me recording it, it was making this noise fairly regularly.

https://youtu.be/dzKbvkLPKX8
 
I dont think that is normal. Does it go away if you open the fuel cap?
You'd have to reference the live data for the EKPS to see if the change in sound corresponds with the activation signal (PWM).

Forgive me if a Z4 does not have an EKPS
 
juld0zer said:
I dont think that is normal. Does it go away if you open the fuel cap?
You'd have to reference the live data for the EKPS to see if the change in sound corresponds with the activation signal (PWM).

Forgive me if a Z4 does not have an EKPS
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Thanks for the reply. I don't know if it goes away with the fuel cap open, I am not even sure whether this noise occurs all the time :/ I'll go and try it in a minute and report back.

It's an E91 but yeah, I'd imagine it would, not sure where to find this in INPA though if you have an idea?

Update: Can't seem to read fuel pressure, reads a constant 600kPa in INPA, released fuel pressure from the rail with no change in that figure. Other people seem to have this issue, potentially a limitation of INPA?

Fuel pump still making the same noise with the fuel cap off. What I did do, was activate the fuel pump with the engine off and it seemed to maintain a normal noise with no fluctuations... I'm not sure what this means :/ Assuming activating it in this way bypasses the EKPS (maybe not) could be the EKPS going bad?

I have always had reservations about fuel pump related failure because I've never had issues with long cranks or anything like that, and because the car seems fine over a certain RPM. So I guess this just adds to my bewilderment.
 
I think the fuel pump noise is a red herring. Was the car revving itself in that video or was someone sat in it? If it was revving itself it would push me even further towards the Valvetronic motor.
 
E91 should have an EKPS under the rear seat bolster, on the right side.
The EKPS is accessible in INPA as a separate control unit.
Disregard the rail pressure in INPA as there is no sensor for it.
Next step is to connect a fuel pressure gauge at the rail and monitor it whilst the noise is occurring.
 
ph001 said:
I think the fuel pump noise is a red herring. Was the car revving itself in that video or was someone sat in it? If it was revving itself it would push me even further towards the Valvetronic motor.
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I was under the impression the fuel pump noise should be constant regardless of RPM, no? And indeed, no one was in the car. I'm going to have to look at the valvetronic screen during startup and see what it looks like. I guess it will still be hard to know because the ECS/VVT position will vary during that time anyway, I guess it's just a question of by how much.

juld0zer said:
E91 should have an EKPS under the rear seat bolster, on the right side.
The EKPS is accessible in INPA as a separate control unit.
Disregard the rail pressure in INPA as there is no sensor for it.
Next step is to connect a fuel pressure gauge at the rail and monitor it whilst the noise is occurring.
Click to expand...

I thought as much, and have been planning to test fuel pressure, I just don't have a tester, so will have to get one some time -.- At least I'm going to be flush with random tools after all of this!
 
There is no way even a fairly major fuel pressure variation would make the revs change like that at idle. This has to be valvetronic motor or cam timing related (VANOS compression rings). Did you change both DISA valves in the end or just the one?

This was my original list right back on page one of this thread....

So I would do in this order:

1) Observe O2 sensor voltages in INPA
2) Fit new battery
3) Replace coil packs and plugs
4) Replace EGR valve and check pipes to sump for blockages
5) Replace / inspect second DISA valve ???
6) Replace valvetronic motor
7) Have VANOS unit stripped and inspected.
 
ph001 said:
There is no way even a fairly major fuel pressure variation would make the revs change like that at idle. This has to be valvetronic motor or cam timing related (VANOS compression rings). Did you change both DISA valves in the end or just the one?

This was my original list right back on page one of this thread....

So I would do in this order:

1) Observe O2 sensor voltages in INPA
2) Fit new battery
3) Replace coil packs and plugs
4) Replace EGR valve and check pipes to sump for blockages
5) Replace / inspect second DISA valve ???
6) Replace valvetronic motor
7) Have VANOS unit stripped and inspected.
Click to expand...

That revving noise is the fuel pump, the engine doesn't rev in tandem with the noise in the video. What does happen though is a slightly audible variation in fuel pump sound when the engine is 'shivering' at idle, which is more like a misfire than drastic rev change, as well as that more obvious noise in the video.

I haven't replaced the large DISA valve, but I've had it out to inspect it and made sure it functions. I by no means think you are wrong regarding the Valvetronic motor or the Cam seals, I just have my reservations, as I do with the other potential problems.

The VVT motor learns positions correctly, and seems to function without issue, no odd noises, seems quick and I didn't detect any shorts in it when poking it with my multimeter. I am going to check the accuracy of it some more this evening when I cold start the car. I have for a long time felt this was timing related because of how mechanically the problem occurs, but this fuel pump noise is just odd and cannot be good and also fits the symptoms, albeit with the usual caveats in that I don't have long cranking issues and I feel like there is a problem when the car jerks when coasting to a stop.

The car is due a service next month and I am wondering whether to put a thicker oil in (5w40, currently 5w30) and see if that makes a difference. If it is the cam seals starting to fail, I'd imagine the thicker oil would make a noticeable difference by maintaining the oil pressure more effectively? I have suspected this was the problem for a while but just can't justify the labour cost for something that is relatively speaking, quite rare.

My plan for this evening

Check rough running and Valvetronic position data from cold start
Check rough running data from cold start with VVT motor unplugged
Drive car with VVT motor unplugged - I am sure I've done this before, but will check again, if problem persists I can rule out a valvetronic fault
 
Keep in mind that valvetronic is not supposedly used during cold start to ensure smoothness. Throttling is done with the throttle body. Have you cleaned yours? Don't spray directly at it. Instead, spray a rag and wipe.
Cold start behaviour can be sporadic but it should always be acceptably smooth.

How full was your tank when you recorded the video? You could also measure pump current draw via the EKPS or if you have a clamp ammeter.

Going back to my earlier post about the fluctuating coolant temps - thanks to all those who enlightened me about the oil temperature management strategy. I monitored it more and I have come to accept it as being normal function. I suppose ambient temps and traffic conditions will determine which reaches 100*c first - oil or coolant.
 
Think you might be getting your terminology mixed up juld0zer....the N52 doesn’t have a throttle body, it increases engine speed by altering the amount of lift on the inlet valves via an electric motor called the Valvetronic motor.

It also has the good ‘old fashioned’ VANOS which alters cam timing in a similar way to the M54.

Ps....the N52 does also have a small diameter auxiliary flap similar to a throttle body, but it’s not used in the same way. It’s purpose is to create a minimal vacuum for the crankcase ventilation and evaporative systems. In practice the flap is always nearly fully open.
 
I actually think you're both a bit wrong here. It seems from empirical findings, that valvetronic does in fact operate during cold start, although I too didn't think it did. The N52 does have a throttle body, but in normal operation remains open so as ph001 says, the valvetronic motor can control valve lift on the intake side. In the event of a valvetronic error, the valvetronic system is completely disabled, the valve lift is set to maximum by the valvetronic motor and the inlet is controlled by the throttle body.

Now for the good sh*t. I just did a cold start which was lumpy as usual and witnessed the valvetronic motor readings bouncing around even when at 660rpm. Based on a couple of seconds at the beginning of this video: https://www.youtube.com/watch?v=EAeKfLAeFZQ there is no movement in valvetronic position during idle. I went right ahead and unplugged the eccentric shaft sensor and it seems to cure the problem, or at the very least, has a significant impact on the smoothness of the idle and driving. Naturally, driving is slightly hindered because it's not really supposed to operate without the valvetronic motor, but it is still much better.

The weirdest thing I witnessed was that there was no EML when unplugging the ESS, but it indeed defaults to use the throttle body to control the intake. This seems to rather promisingly point towards the Valvetronic motor as my issue... What do y'all think?!
 
I have to ask - can you operate without the ESS - I've unplugged mine during running before and it's made the engine turn off...
 
Capa said:
I have to ask - can you operate without the ESS - I've unplugged mine during running before and it's made the engine turn off...
Click to expand...

As in the post above yours, yes you can :thumbsup:
Rob
 
Capa said:
I have to ask - can you operate without the ESS - I've unplugged mine during running before and it's made the engine turn off...
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I mean, I unplugged that bi*ch and then started it so it knew not to use valvetronic. With the engine on I'm sure it doesn't like it, so I'm not surprised yours tapped out.
 
Update

Been driving the car with the ESS unplugged today, and although it's smoother, I don't think the problems are gone. I'd imagine the reason for this is just that the car is operating to higher valve tolerances, so any problems seem less prominent.

I have however since discovered how to look at EKP data in INPA and I don't think it looks normal at all, PWN seems eratic, "engine voltage pump" whatever that means, I am assuming voltage at the fuel pump seems low, the current draw is fluctuating a lot at idle and the "actual engine speed pump" which I am guessing is the fuel pump rpm is all over the place, especially when compared to the target pump speed which remains stationary. Here is a video of the screen during idle and when revving: https://youtu.be/dCZPDdN44Uw

I can find literally nothing about people using INPA or anything else for that matter to investigate the EKP to get any figures to go by. The only thing I can find are some still shots from a guy who has a 530 and his voltage is always above 12v. Obviously I can't tell from that what whether his other values fluctuate.
 
On years of being on this forum I have never heard of a single N52 fuel pump related problem....that’s not to say it can’t happen, only that I think it’s extremely unlikely. Whereas I’ve seen a handful of Valvetronic motor issues.
 
Slight update

So I messed around unplugging my VANOS solenoids in the hope that it'd help me narrow this problem down. My idea was that if the symptoms were as a result of VANOS issues such as bearing ledge or rectangring wear, with VANOS is disabled the problem should stop. The problem did not seem to stop, which makes me lean back towards valvetronic.

I got ISTA up and running to try the valvetronic relearn procedure available on there. After doing this then starting the car, the idle was worse, but don't think there was much change to drivability. This makes me think something funky is going on with the motor more so. As a result, I have managed to snag a used genuine valvetronic motor to try as I am not willing to punt over £100 quid on what is essentially another guess. The motor will take a while to arrive, so I guess this will have to wait until then!

The only other thing I have read about since, is being able to change the valvetronic minimum lift, which admittedly I haven't read into much, if at all, but will be something I'll also look into.
 
I think fitting that replacement Valvetronic motor will be a crucial step...and may turn out to be a very happy day for you.
 
ph001 said:
I think fitting that replacement Valvetronic motor will be a crucial step...and may turn out to be a very happy day for you.
Click to expand...

Well, I certainly hope you're right! I've got most of the bits for this month's service too. Although, I've got this terrible feeling that as soon as I do a coolant flush, my water pump is going to fail, I'm being optimistic though! Haha
 
Valvetronic motor comes today. Brace yourselves for some excellent or disappointing news this evening. As a secondary update, the hesitation and stuttering seems to be getting worse, which is in line with the BMW bulletin about this/similar issues.
 
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