Newbie to Z4, boggy and surging acceleration

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Naylz
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Newbie to Z4, boggy and surging acceleration

Post by Naylz » Wed Mar 13, 2019 9:58 am

Hi everyone, just bought my self a 2008 2.5se Z4 roadster, picked it up last week and now I've noticed that when I accelerate it feels like it bogs down a bit and then the acceleration picks up but in what I can only describe as like a surging pattern, you can see the rpm needle increase in steps. At first I thought this was maybe due to some crud being drawn through it as the dealer had been allowing test drives whilst the car was on pretty much empty. I have tried some redex cleaner to no avail. Taking it back today for them to have a look at. It hasn't got any warning lights on the dash so guess there's no fault codes?? As I say I'm a newbie to BMW so any help or advice will be welcome. Thanks in advance

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ph001
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Newbie to Z4, boggy and surging acceleration

Post by ph001 » Wed Mar 13, 2019 10:13 am

Search vanos solenoids as a starter. Cheap and easy to replace if that's the problem. If not, you are probably looking at issues with either the eccentric shaft sensor (check for oil contamination) or the valvetronic motor.
2007 E85 Z4 3.0Si manual :driving:
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Naylz
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Newbie to Z4, boggy and surging acceleration

Post by Naylz » Wed Mar 13, 2019 10:27 am

Thanks, I did have a look at the vanos solenoids, gave them a spray with some carb cleaner. To be fair they didn't look what I would consider dirty ( bearing in mind my other car is a 300tdi defender). I didn't disconnect them either as I didn't want to throw up a fault code that the dealer could then claim I had tampered with it. They did have the BMW logo on so maybe originals?? How long should they last? This z4 is on 89000miles. When I described the fault to the dealer he said maybe a coil breaking down or a clogged filter...but obviously he will have a better idea when he drives it.

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ph001
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Newbie to Z4, boggy and surging acceleration

Post by ph001 » Wed Mar 13, 2019 2:20 pm

Surging as you describe is certainly not a common problem on the N52. The inlet manifold has different tuned lengths to it which are controlled by two flaps called DISA valves. A fault there could cause surging at a couple of points in the rev range but BMW revised the design substantially from the M54 engine and failures there are not common now.

You may have some 'soft' fault codes stored even though you have no lights on the dash so worth putting on the diagnostics still. One thing you can do with the solenoids is simply swap them over - on the assumption they are not both similarly faulty, it might tell you something.

A coil breaking down is a pretty obvious misfire so I doubt it's that. Never heard of a blocked filter (assuming fuel filter) on these cars either but if it's been run on vapour with some sludge in the tank I guess it's a possibility. Doubt it though.
2007 E85 Z4 3.0Si manual :driving:
19" CSL's | Eibach Springs | Aeroskirts | Z4M front bumper | Clear brake light | ZHP | RCH+| Stubby

2004 E46 M3 coupe manual.

Naylz
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Newbie to Z4, boggy and surging acceleration

Post by Naylz » Wed Mar 13, 2019 4:21 pm

Thanks for your replies. I have just got back from the independent dealer I bought from, the mechanic drove my z4 and straight away noticed what I meant, i.e. The surging on acceleration. He then plugged in a snap-on diagnostic tool, searched for fault codes but for some reason the diagnostic tool was very slow and came up error each time he tried it. So he tried a reset codes and then we went for a drive and the surging had gone, acceleration noticeably smoother. Problem now is we have no idea what codes may have been there, so he suggested running the vehicle and if it starts surging again fetch it back, in the mean time he will get his diagnostic tool updated as he said there was too much stored data on it from other vehicles. So as you say there may have been some codes on there that were somehow confusing the way it was running?? I'm guessing that whatever codes they may have been should flag up the engine light if they reappear?? Or is that not how it works?

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Newbie to Z4, boggy and surging acceleration

Post by Naylz » Wed Mar 13, 2019 4:26 pm

Oh and what would I expect to find if I swapped over the solenoids? If one was faulty and say after swapping the surging went away does that say it's inlet or exhaust solenoid at fault? Oh and when unplugging the solenoids does that automatically flag up the engine light/ fault code that would then need resetting? Or does it not notice the unplugging with ignition off? Thanks again

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Post by andyf1140 » Wed Mar 13, 2019 5:33 pm

Naylz wrote:
Wed Mar 13, 2019 4:26 pm
Oh and what would I expect to find if I swapped over the solenoids? If one was faulty and say after swapping the surging went away does that say it's inlet or exhaust solenoid at fault? Oh and when unplugging the solenoids does that automatically flag up the engine light/ fault code that would then need resetting? Or does it not notice the unplugging with ignition off? Thanks again
That wouldn't trigger a fault unless you failed to reconnect them properly.

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Post by Naylz » Wed Mar 13, 2019 5:59 pm

Thanks

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ph001
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Post by ph001 » Wed Mar 13, 2019 8:01 pm

Its a shame he screwed the code read up but I guess they will reappear if the problem returns (which doesn’t necessarily bring a light on).

You can do anything to the vanos solenoids with the ignition off as the car is not looking at any signals until the ignition is on.

If swapping them made a difference I would just remove and thoroughly clean both with carb cleaner. If that didn’t sort it I would replace them both considering what thay cost.
2007 E85 Z4 3.0Si manual :driving:
19" CSL's | Eibach Springs | Aeroskirts | Z4M front bumper | Clear brake light | ZHP | RCH+| Stubby

2004 E46 M3 coupe manual.

Naylz
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Newbie to Z4, boggy and surging acceleration

Post by Naylz » Thu Mar 14, 2019 6:18 pm

Bit of an update, the surging acceleration came back. However I had ordered a BMW code reader which arrived today so here is what it came up with;
2A39 valvetronic, adjustment range
2E69 Knock-sensor signal 2
2E68 Knock-sensor signal 1

I tried to erase them and the knock sensor ones cleared but the valvetronic one came back straight away after just starting the engine once (not gone for a drive). Tried another erase and this came up once engine started again;
2A43 valvetronic, thermal overload protection: warning threshold
2A40 valvetronic, thermal overload protection
2A39 valvetronic, adjustment range
Anyway called the dealer and gave him these codes, he started talking Vanos and sensors but assured me he will fix it 😎 Would anyone know what he is likely to be fixing here? Is it the valvetronic motor I would expect to get renewed? Just would like to have a clue as I don't want to be fobbed off with some kind of temporary fix.

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ph001
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Newbie to Z4, boggy and surging acceleration

Post by ph001 » Fri Mar 15, 2019 2:32 am

I can’t imagine why he would be even mentioning vanos, and that would set the alarm bells ringing right now for me. This will be valvetronic motor or eccentric shaft sensor related. If he starts wanting to take the vanos apart you need to go somewhere else.
2007 E85 Z4 3.0Si manual :driving:
19" CSL's | Eibach Springs | Aeroskirts | Z4M front bumper | Clear brake light | ZHP | RCH+| Stubby

2004 E46 M3 coupe manual.

Naylz
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Newbie to Z4, boggy and surging acceleration

Post by Naylz » Fri Mar 15, 2019 7:23 pm

I will be having words with him before vehicle is handed over, that’s exactly why forums like this are so useful, a bit of knowledge helps. Thanks

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tug
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Post by tug » Sat Mar 16, 2019 7:13 am

Deffo needs a new valvatronic, mine did exactly the same. Got a new one fitted been perfect ever since.

Cheers, tug :thumbsup:
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Naylz
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Post by Naylz » Sat Mar 16, 2019 8:30 pm

By that I guess you mean the actual motor? I did notice quite a bit of oil around the coil pack wells in the area of the valvetronic motor when I took the engine cover off, to be fair I thought it was from someone slipping with the oil can when refilling it during its recent oil change. Can't wait to get it sorted then I can really start to enjoy driving it 😎......it has literally rained every single day since I bought it, on a positive the roof doesn't leak 😎😎

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Post by tug » Sun Mar 17, 2019 7:46 am

Yes, it also sorted a niggle with the idle. On tickover mine was rough, you could see the gearstick moving with the 'beat' of the engine. But i just put it down to the '2.0 gremlins.' Since havin a new valvatronic its as smooth as silk. :)

Now i aint sayin that 100% that it is your problem, probably 95% sure. Cos the cost of a new motor fitted is @ £400 all in and wouldnt want you to outlay that sort of money and it not be the problem. Had mine done at a BMW indie it would be hell of a lot more at the stealers.

Mine eventally went into limp mode which forced me to have the job done. As i say though your symptoms are almost identical to what happened to mine. Hope everything turns out good for ya buddy so you can :driving: now the weather is slowly gettin better for us.

Cheers, tug :thumbsup:
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