Newbie to Z4, boggy and surging acceleration

[Naylz]

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

 

[ph001]

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.

 

[Naylz]

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.

 

[ph001]

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.

 

[Naylz]

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?

 

[Naylz]

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

 

[andyf1140]

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.

 

[Naylz]

Thanks

 

[ph001]

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.

 

[Naylz]

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.

 

[ph001]

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.

 

[Naylz]

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

 

[tug]

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

Cheers, tug

 

[Naylz]

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

 

[tug]

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 now the weather is slowly gettin better for us.

Cheers, tug

 

[andyf1140]

I had the same thing, used a cheep ebay special and it was great for a while but it's starting to have the classic rough idle

 

[Naylz]

Well, fast running out of patience with the dealer, took it in Wednesday, gave them a print out of the fault codes, told them I thought maybe valvetronic motor. Today he tells me he still doesn’t know what’s wrong with it, he has ordered a new valvetronic....I asked did he mean the motor....er yeah but to be honest if that doesn’t fix it then he feels he is out of his depth!!!

Great, not sure what to do now, had it less than two weeks, love the car but I’m now worried it isn’t going to be sorted right

 

[tug]

GET OUT OF THERE FAST AND DONT PASS A PENNY OVER. He obviously knows very little He doesn't know BMW and to fit a valvatronic you need a certain amount of knowledge. The engine 'fits it' by the mechanic knowing where to place the motor and using ignition control. Damage can be caused if not fitted professionally.

Hope my advice helps buddy.

Cheers, tug

 

[Naylz]

Well today I finally got my Z4 back and touch wood it all seems to be fixed. It has been nearly three weeks since handing it back with the issues it had, very long story short they tried cleaning various sensors, that fix it, they ordered a new valvetronic motor, this took a week to come and then was the wrong part, so they ordered the correct one after I gave them the part number, this took another week to arrive, they then fitted it and the car wouldn’t start (yes they did program it first) turns out the new part had been damaged in transit and was bent....I was then told that they are rarer than rocking horse poo and even BMW has a wait if one month to get one....so I rang BMW and they got one the following morning. This then got fitted all seemed hunky dorey they delivered it back to me, I drove it and the surge was gone, parked it on my drive and checked for fault codes of which there were quite a few, valvetronic adjustments, some plausibility ones and others I can’t remember, the delivery guy/ mechanic was still with me so we cleared the codes and surprise surprise it then wouldn’t start. So off it went back to the garage, I said that I thought it was the eccentric shaft sensor as that was common to all the codes bearing in mind the motor is a genuine BMW brand spanker. The following day the garage said they had taken it to BMW and had been advised to check the eccentric shaft sensor for oil, This turned out to be the culprit, so a shiny new sensor from BMW now fitted and all seems good, no surging on acceleration, no bogging down and a rock solid steady idle. So in summary I believe both parts were at fault, costly parts too, luckily I didn’t have to pay a penny

 

[andyf1140]

Very lucky and a great outcome