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Hillview550

Surging issues - 550i

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Hi all yep I'm new to this, Im' afraid I'm bit of an old fart now but need some help and advice...

 

I Have a 2006 550i msport, fantastic thing and to some extent reminds me of my racing days, BUT I have a problem;

 

It surges slightly under light throttle load up to 1700 rpm, this is enough being an auto that it plays havoc with smooth changes and general driveability.

 

Both Bosch and Autologic find no DTC's 

 

On idle thru to 2500 rpm at stand still the charge rate is a consistent 14.2v 

 

Check gearbox fluid level - all OK - on very light feathering gear changes are as once was smooth....

 

Battery, Plugs, coil packs, MAF, Fuel filter, CCV, vacuum lines and checks for air leaks, respective sensors, etc, etc, have been cleaned, checked or replaced (mostly replaced) and adaptions reset ! 

 

So I am at a loss....can anyone advise me with any similar experiences ?

 

 

Thanks for your time.

 

 

 

Jonathan 

 

 

 

 

PS. Ive renewed vacuum pump it whined loudly BMW dealer said they whine some anyway !!!! - is this true ???

 

 

Edited by Hillview550
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Welcome.  I'm not an expert here, but I wonder if it is not the engine at all, and perhaps something like wear in the torque converter.

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Not 550i but 545i with the same N62 engine  My vacuum pump was silent.  It leaked oil between the joint with the upper timing case but no whine.

 

What rpm does it surge between?  Mine surged between 1000 and 1200 rpm but not as high as that.  Does it do it in all gears?

 

Possibly TC lock up clutch issue.  Have you had the codes read?

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My experience is mainly limited to diesels....however...

 

A TC lockup fault tends to make the revs dip up and down but you don't really feel it in the car. The car dithers up/down between two gears but the changes are smooth and it doesn't really come through to the car.

 

A vacuum leak can cause oscillations in power because whatever is being commanded doesn't respond quickly enough. Again that is particularly with diesels, on these it can surge on EGR control and vacuum controlled variable turbo control.

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This may sound bizarre and is a long shot but it's free and simple to check: My 645ci had a similar issue, albeit intermittent. The terminals on the temperature sensor on top of the thermostat housing were not making perfect contact and this was sending a fluctuating temperature reading to the DME. The gearbox behaves slightly differently depending on coolant temperature (probably combined with gearbox temp as well but who knows). As the connection varied the gearbox very clearly changed the amount of 'slip' going on and that caused fluctuating surges. It was enough to clearly feel it as the car drove, even at lower motorway speeds when on a light throttle. I thought the gearbox was about to die in an expensive way. I too checked voltage as I had been having alternator issues before and that was fine but while I was in the 'secret menu' I looked at coolant temp and it was jumping by many degrees sporadically, which coincided with the surging. A quick clean up of the terminals resolved it.

 

My vacuum pump is virtually silent, I certainly don't hear it above the injector and vanos racket. It happens to be the only place on the entire engine that isn't dripping in oil...

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Hi 

 

Thank you for your replies and experiences.....

 

The car surges in all gears - its probably fluctuating say around 200/300 rpm between 8-900/1000 rpm up to 1700 rpm or so, seems to be relative to the speed I'm doing, the higher the gear and speed the less impact is has (1-200rpm), sometimes the shift from say 1st to 2nd is slightly jerky same into 3rd and 4th (but its occasional, because I'm conscious of it therefore must be relative to throttle load with my foot !!) further up the gears at lower speeds its smooths out, I guess this is due to higher rations in those gears smoothing the changes, but the surging is there 100-200rpm if that on light throttle when poodling along within the rev range I described...Give it some to power away, it would seem that depending on whether its at the bottom or the top of the surge (power on or slightly off) this affects the changes on kickdown to being clean and direct or to a slightly hesitant and jerky gear selection followed by initial hesitant power delivery once in that gear... then it goes like the proverbial .... Odd I know, hopefully my description makes sense to you all.

 

In tip/manual I can smooth this out a little more because one tries and is compensating for it. 

 

When I originally plugged into both machines - Bosch and Autologic, there were no DTC faults .... and none for the temp, TC or G/Box, I did plug in again and again nothing for the the aforementioned ................... I haven't checked the temperature either via the menu or on a diagnostics machine. It's a bloody good point, I shall look at this tomorrow. 

 

The Vac pump isn't intrusive and doesn't leak oil...its a niggle really, just want it right, I'll get to it when Ive got to the bottom of the surging. 

 

Many thanks for your help with this so far.

 

Pls feel free if you have any further thoughts and ideas, much appreciated.

 

Regards

 

 

Edited by Hillview550

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Does the surging happen in neutral when you rev it slightly or is it only on load? Does it happen as constant up-down kind of thing or is it just one surge as it changes gear or perhaps random but repeating?

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Hi

 

Yes it does do it when in neutral / park, and it is constant if I manitain feathering thr throttle, I can kind of compensate for it by lifting when changing up a gear, on kick down it seems to depend on whether its at the top or the lowest ends of the surge !

 

Could it be theres maybe a small vacumm leak or as mentioned above a temp signal flucating and the ECU adjusting on the fly ??

 

One thing it has had is new CCV diaphrams .....could this mimick the symptom discribed ?

 

Regards 

Edited by Hillview550

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Perhaps that rules out the gearbox.

 

I had a pulsing kind of surging happening when cold at idle that turned out to be the alternator, even though the voltage looked reasonably stable on the secret menu. The load was going up and down to maintain that fixed voltage. It got so bad I could see the alternator belt tensioner moving in and out as it loaded up with each surge. I used an oscilloscope to see what was happening and there was a clear noise appearing on the output in time with the load changing. A replacement (used) alternator resolved that one but I could probably have just done the regulator.

 

You should try simple things first like turning air-con off, just in case that is making a pulsing load.

 

Now might be a good time to get INPA working on a laptop as it is possible to view very fast live data from the N62 DME, including torque loading from the air-con compressor and torque loading from the alternator as well as vanos angles, valvetronic lift etc. etc. Some of those useful screens are hidden under the 'FASTA' menus. Without data like that it might be difficult to get to the bottom of this. Air leaks would most likely cause fuel trims to be obviously out. I don't remember ever reading about surging being caused by leaks but these engines have such a complex way of adjusting idle speed that it wouldn't surprise me.

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Hi Thank you for your input and ideas, I shall be looking into the secret menu this afternoon, but INPA is something I'm going to struggle with in darkets Dorset !

 

Is there somewhere I might be able download a copy from somewhere ? I have an data OBDII lead and windows based laptop I can use....

 

Jonathan

Edited by Hillview550

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Yeah doesn't sound like it's the box. Which is a relief.

 

I had a fault with my crank case breather valves which gave me rough running. Fault code was for lean running due to too much air.

 

Sounds like air or vacuum leak on secondary air side. There is no vacuum in the inlet manifold on these engines as the throttle works by opening the inlet valves more this is controlled by the valvetronic system, could be a fault in that too giving the fluctuations in revs.

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Does the surging happen during the first minute or so of cold running? The valvetronic system is inactive until the engine is warmed for a minute or two. During that phase it uses the throttle body to control the air flow and the valves are at full lift. If it is perfectly smooth during start-up then it might point to valvetronic issues.

 

How many miles has the car done? Has it ever had the pre-cat 02 sensors replaced? They are wideband ones, which I must say I've not had to test before. A good scanner or INPA showing live data might show the surging is actually the mixture control hunting due to a lazy 02 sensor. The engine will run open loop for a short while when cold so the sensors are ignored. This could also give smooth running at first, so mixture control or valvetronic issues can both be masked at start up and would need a bit more work to separate. I think the closed loop control with 02 sensors settles before the valvetronic cuts in so it might be possible to judge which area is at fault without starting to unplug things.

 

I don't think the valvetronic system does all the control of idle / light running though as the minimum valve lift sits rock steady at 0.30mm (from memory) while idling. That means either the vanos is fine tuning the idle (the angles are constantly shifting on idle) or the throttle plate does come into play to some extent. I have never had reason to dig deeper but I'm intrigued to know how they do it! So, it could even be vanos related, or due to the throttle body. Ugh too many variables! If a valvetronic motor is unplugged before the engine is started the system runs fail-safe and leaves the valves fully open and controls using the throttle. That can be a further way of eliminating some things but it throws a load of codes and if you don't have means of reading and clearing them that might cause some confusion at a later point.

 

OP states the CCV are done (I assume you mean the orange rubber valves in the cam covers). I thought air leaks tend to give rough 'hiccup' type running issues rather than a surging sensation. Apparently a common place for air leaks are the seals around the valvetronic sensors at the back of each cam cover. The fault is always described as rough running though. Just to clarify, this isn't a stumbling then recovering type sensation you are experiencing is it? I would describe surging as revs smoothly dropping and then pulsing back up again rather than a rough hiccup / stumbling type effect.

 

 

 

 

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I'm looking at the car again this afternoon, have access to a Bosch machine not sure if it can interigate with live data tho... shall try

 

The INPA i see some internet downloads available, is there a preference that you could guide me towards ?

 

Many thanks Jonathan

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Hi All , well am further ahead.... would appear that the alt regulator is playing silly buggers ! charge rate is a sustainable 14.2 at teminals but on secret menu in car the charge in realtime drops to 12v ... so now trying to source a regulator and Valeo doesnt have any ??

 

So now ringing around, Alt is out so now a priority...

 

Does anyone have any sources that can supply ?

 

Thanks for your input and guidance.

 

Best J

 

 

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On 03/12/2018 at 20:09, Hillview550 said:

When I originally plugged into both machines - Bosch and Autologic, there were no DTC faults .... and none for the temp, TC or G/Box, I did plug in again and again nothing for the the aforementioned ................

 

Is your diagnostic tool definitely compatible with your car? As some older machines will struggle to read your car, as I belive for the facelift E60 they changed the pins in OBD Connectors. I found this out the hard way when my e46 cable didn't work on my e60, I had to buy a different cable. Only reason I am mentioning this as you have no codes whats so ever. There is usually something that always logged, even if its pre-historic but I could just be thinking of INPA, which reads historic logs. 

Edited by Mr_530i

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5 hours ago, Hillview550 said:

Hi All , well am further ahead.... would appear that the alt regulator is playing silly buggers ! charge rate is a sustainable 14.2 at teminals but on secret menu in car the charge in realtime drops to 12v ... so now trying to source a regulator and Valeo doesnt have any ??

 

So now ringing around, Alt is out so now a priority...

 

Does anyone have any sources that can supply ?

 

Thanks for your input and guidance.

 

Best J

 

 

So the same issue I had, simple enough to fix at least! I bought a used alternator from Quarry Motors for around £120 from memory. I too couldn't find a regulator in a hurry. A new alternator is daft money.

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HI me again !!

 

 

Well new valeo regulator fitted Alt back on car .... secret menu now shows a 14.2/3v when revved the values go up and not down as previously !!! to a max of circa 14.8/9

 

Also when revved the curtosy lights flicker/dim momentarily ? Battery is a £200, Ive tried 2 other batteries and the symptoms are the same.

 

The car still surges ? in park.

 

Does anyone have any other ideas ?

 

The batt terminal intelligent charging sensor thingy has been plugged in and unplugged and makes no difference to the above.

 

Regards and seasons greetings

Edited by Hillview550

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Hi

 

Am now completely bewildered....plugs been out, coil packs checked (no DTC's) ... the only thing I can think of is to collate sensor values and run function tests within Bosch and Autologic which I have have access to. 

 

So can anyone help me with the what values should be across the relative sensors ??

 

Lamda,

O2, 

Inlet pressure

Water Temp

Knock

Vanos

Crank 

Cam 

 

....etc etc 

 

 

Regards

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Is the alternator now steady at idle with no pulsing visible at the belt tensioner? It was really obvious on my 645 when the alternator was loading / offloading as the belt tensioner moved several mm in time with the surges.

 

Digging further into the diagnostics, I would suggest you look at live values for the fuel trims and see if it is shifting with the surging. That might help point to a slow 02 sensor or bad MAF sensor. I appreciate you have replaced the MAF but don't rule things out too soon as new parts can fail. BMW software refers to Lambdaintegrator or similar which is a reasonable equivalent of a short term fuel trim. The Additive and Multiplicative figures should be close to zero. Highly positive Lamdaintegrator or Additive figures point to air leaks. I'm not sure how the Autologic / Bosch units report fueling data.

 

Did you check the aircon pump isn't loading up and causing this (switch off air-conditioning)?

 

Also, whether or not this issue presents straight away at cold start-up could help you narrow it down. The system runs open-loop at first before the MAF / O2 sensors are used. The valvetronic system is also bypassed for the first couple of minutes. If all is smooth at first then it could be down to one of those systems.

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