Rough running N52B25 2.5i

[JonBooth]

Hello everyone,

I was hoping someone may be able to help. I've had my 2007 Z4 2.5i for around a year and a half and have an intermittent problem where the car starts stuttering and misfires really badly. This first happened after a few months of ownership and when I plugged the car in, it logged a P1554 fault. My friend (BMW Technician) and I thought it was most likely the Vanos solenoids so removed them both, cleaned them and cleared the fault.

The car was then okay for months until November ish last year where the same thing happened. After the rough running the engine died (naturally blocking a slip road) and wouldn't restart for around 10 minutes. The car turned over fine and would fire but would then stutter and cut out again.

After 10 minutes or so, the car was back to normal. It was due in for a service in December so I brought it forward so they could have a look at the same time. On the way to the garage the same thing happened but I just about managed to keep it going to get there.

When they had a look, I think they said there were no faults logged on the ECU but they think it would most likely be the vanos (it was either this or the same fault as before, I can't quite remember), and we thought it could have been down to poor quality/wrong grade oil from the garage the car was purchased from. They said they cleaned the vanos solenoids but that they weren't dirty and looked fine.

I thought this was fixed but then the same thing happened on Saturday (7th Feb 2015) although the car didn't completely fail. Once I turned the engine off and gave it a minute or two, it fired back up and has been fine since. I've plugged in my reader and there are no faults or lights present.

Has anyone else suffered from the same symptoms? If so, what was the cause in your car? I think it is most likely to be the Vanos but there are many things it could be and I don't want to start changing sensors that are not the cause if I can help it, it's frustrating with it being so intermittent as I won't know if I've fixed it for potentially months. It's also worth mentioning that ever since I've had the car, sometimes when I slow down at a junction the revs almost seem to drop too much and then come back up, I have a feeling that this could be related.

Thanks in advance for your suggestions.

Cheers,

Jon.

 

[Smartbear]

i thought that if the vanos was faulty it just caused a drop off in performance & not missfiring issues, sounds more ignition related, coil pack etc?
regards

 

[Ewazix]

The P1554 fault can be quite generic, some people have ended up cleaning or changing the whole VANOS, and plugs, and coils, and cam position sensor then found it was a vacuum leak or even a burnt valve. Not a lot of help I know but there are a few threads on it with ideas but few solutions, good luck. :|

 

[JonBooth]

Thanks for the replies, I know what you mean and it could be a coil but if the Vanos system failed the cars timing could be advanced preventing the car from running correctly.

As you mentioned there are quite a few things it could be, I've checked all the hoses and can't see any splits or damage, the breather was replaced fairly recently anyway. It's tricky with it being so intermittent as it's hard to know whether it's fixed or not.

Thanks again for the replies so far.

Jon.

 

[Swiftly]

My zed has recently been generating a check engine light and P1554 error. As well as the Vanos solenoids cleaning the dealer also checked the cam position sensor and engine timing as part of the diagnosis process as determined by their software. My Vanos solenoids were finally replaced at the stealers under Insured Warranty as they kept generating the P1554 code intermittently. However once replaced I then started to experience misfiring and drop in power under load. The dealers had to reset the Vanos Unit and Vanos solenoids back to factory settings using their software so that the system starts to re learn and generate new curves. From my understanding the initial reset they did hadn't taken correctly, hence a second reset. My understanding is if the system isn't reset and the curves are out of sync, then the Vanos system and solenoids can end up competing with each other and trying to constantly compensate for the imbalance, hence the timing issues and misfiring and loss of power.

Hope it helps and you get it sorted Jon

 

[JonBooth]

Thanks for the reply Swifty. I think this could well be the issue with mine. It's very intermittent but I think it may well be worth changing the Vanos solenoids. I'll have a ring around to get some prices for the parts.

Thanks again.

Jon.

 

[JonBooth]

Hello again everyone,

The car had another wobble on Saturday morning (21st). Sat at 50 in 6th gear, the engine was doing around 1800 RPM, I then felt a slight stutter and the revs started fluctuating slightly at constant speed. As the speed increased to 70 the stuttering became less apparent but I could hear a slight misfire and if I slowed back down to around 50, the stuttering returned, the car also felt very flat. The first time I had to stop, the engine died but started back up on the first turn of the key.

Other than being a bit flat at first, the car has been fine since it was restarted and yet again there are no fault codes. I rang my local dealer and the Vanos solenoids are around £86 each but I am still reluctant to buy them as I am still not sure if these are the culprit although it does seem likely. Has anyone else had similar symptoms?

Thanks again,

Jon.

 

[Swiftly]

Hello again everyone,

The car had another wobble on Saturday morning (21st). Sat at 50 in 6th gear, the engine was doing around 1800 RPM, I then felt a slight stutter and the revs started fluctuating slightly at constant speed. As the speed increased to 70 the stuttering became less apparent but I could hear a slight misfire and if I slowed back down to around 50, the stuttering returned, the car also felt very flat. The first time I had to stop, the engine died but started back up on the first turn of the key.

Other than being a bit flat at first, the car has been fine since it was restarted and yet again there are no fault codes. I rang my local dealer and the Vanos solenoids are around £86 each but I am still reluctant to buy them as I am still not sure if these are the culprit although it does seem likely. Has anyone else had similar symptoms?

Thanks again,

Jon.

Since there are no codes being recorded Jon, have you thought about swopping the intake and outlet Vanos solenoids since they are interchangeable and a relatively easy job to do, that way you could see if you notice any different symptoms or if any error codes get recorded.

 

[MrPT]

I've had a few "wobbles", accompanied by a P1554 or 2A98. Identical symptoms to you - a misfire then a lot of trouble maintaining idle, and then completely back to normal after a few minutes/restarts. Essentially the same engine too.

I think it's oil-related because it has always happened simultaneously with the oil light (+1L) or just after it, and/or when the weather is very cold and the engine is getting up to temperature. A local indie told me that cleaning the Vanos solenoids won't always fix it because they can always get clogged again immediately if the oil quality is bad. Even a brief blockage can trip the engine timing. He suggested only using fully synthetic, approved oil and doing a proper oil change (i.e. drain the sump, don't pump it out) at least once a year.

 

[Swiftly]

I wonder if it might be related to an intermittent fault with the camshaft timing position sensor

 

[BrianD]

If not Vanos solenoids then it might be a timing related fault

 

[JonBooth]

Thanks again for all your replies. I may have to try that Swifty, it'll be interesting to see if it makes any difference.

My first thought was that it could have been oil related and we thought the garage the car was purchased from may have put either cheap or the incorrect grade of oil in which could have caused the issue.

I had it serviced recently though (in December) and it had a genuine oil filter fitted along with Castrol edge oil (5W30 I think off the top of my head). The Vanos solenoids were removed and cleaned at the same time and all looked okay. I thought it was fixed until it happened again the other week but this leads me to think the oil isn't at fault this time.

My friend and I thought it could be an issue with the cam or crank sensors. I think it is most likely to be the cam out of these two though as there are none of the starting symptoms of a crank sensor. I'm tempted to just bite the bullet and buy two new solenoids.

Thanks again.

Jon.

 

[Scooba_Steve]

Having just replaced a VANOS solenoid I'll give you my symptoms:

Occasionally (once every few weeks) there would be a hesitation at low speed (~40) with steady throttle for a fraction of a second. No EML except once which then went away. Codes were present though relating to sensor jammed and crank timing. Interestingly my issue started after an oil change (the stuff that came out was black and nasty looking - and at only have the oil service interval).
Tried cleaning which worked for a while then back to the same. The diagnostic process is to swap them and see if the fault follows, I personally didn't bother and just put a new one in. In your case I don't think it's going to be the solenoids but swapping them over can't hurt, saves paying someone to do it for you as part of the diag process!

Hope you get to the bottom of it mate.

 

[JonBooth]

Hello Steve,

Thanks for the reply, I'm away this weekend but I may do it the week after. Out of interest what makes you think it isn't the solenoids in my case?

I hope I get to the bottom of it too. Thanks again for the reply.

Jon.

 

[Scooba_Steve]

I would have thought that it was unlikely for the VANOS solenoids sticking to completely kill the engine unless it was the ECU shutting it down for protection. I don't know if it can do that and would expect a more descriptive fault code if it did.

But I really don't know the systems; serious missing sounds more ignition or fuel related to me though. That being said my windows were playing up and a new battery seems to have cured that - a battery check couldn't hurt either.

 

[JonBooth]

Hello again everyone,

Thanks again for the replies. Here's a link to a video of the issue from 7th February, it's not very good as you can't really hear the engine (it was running horribly and misfiring) but you can see the rev counter.

http://youtu.be/Ex6uyUGisV0

Cheers,

Jon.

 

[Scooba_Steve]

Poorly car.

Are you able to read the codes? You're not going to get a definitive answer from the video I wouldn't have thought. Read the detailed faults and see what it throws up. Having had a look on the interwebs P1554 has been solved with VANOS solenoids but that usually throws another code too. I'd still be tempted to swap them and see if the fault moved.

 

[Smartbear]

Have you tried running the car with the MAF disconnected?
Regards

 

[JonBooth]

I've tried reading the codes myself but most of the time it doesn't throw a code at all, when it has it's only shown the P1554 fault. Luckily enough, it was running like this when I took it to the garage for a service in December so I was hopeful they'd be able to diagnose it as their fault code reader is a much higher spec than mine (the two guys are BMW Technicians who set up their own garage) but their fault code reader didn't show anything other than the P1554 fault either. They thought it looked like Vanos at the time.

I may swap them round after this weekend but it's so intermittent and rarely throws a fault code so it would be difficult to see if there is any difference. The last two times it happened there was no fault.

I haven't tried disconnecting the MAF sensor. Could this cause these symptoms? Yet again it's extremely intermittent.

Thanks again.

Cheers,

Jon.

 

[JonBooth]

Hello again everyone,

Based on everything that's been said and everything I've read, I've decided to bite the bullet and have ordered two Vanos solenoids from my local BMW dealer. I've checked the eccentric shaft position sensor for oil and that all looks okay (it was mentioned that this can sometimes cause similar issues). I'm going to fit the new solenoids next week. Fingers crossed this fixes the issue. I'll keep everyone posted.

Cheers,

Jon.