N52 hesitation, stuttering, jerking, surging etc

[propaintballa]

Have you driven your car with the maf disconnected so it runs on the default map? If it runs well it points to a faulty maf.
Rob

I have and it didn't make much difference as far as I remember. I could try it again. What I do remember though was when I disconnected the pre-cat o2 sensors and the problem seemed to go away. So I replaced the o2 sensors thinking I had found the smoking gun, and the problem was still there :/ Wasn't sure what to make of that. Still not sure to this day!

 

[Fadi-shamleh]

Did you tried to reset the transmission values? Is your transmission oil temperature normal? I think the problem is related to the transmission not to the engine, torque converter maybe, I am now testing some issues with the transmission and I hope to find the answer soon.

 

[propaintballa]

Did you tried to reset the transmission values? Is your transmission oil temperature normal? I think the problem is related to the transmission not to the engine, torque converter maybe, I am now testing some issues with the transmission and I hope to find the answer soon.

Mine is manual, so this does not apply to me. However, if you have an auto, particularly an auto with 80,000+ miles on it, a transmission service (fluids and filter) and a transmission adaption reset would be the first thing I'd do. A lot of these symptoms are seen in auto cars that haven't had a service.

 

[Fadi-shamleh]

My car engine code is N52B25AE with the black plastic cover, I installed it from an 2009 E90 sedan comes from Japan but I couldn't find how much horsepower it's produce, can anyone help please

 

[Joycey]

Really enjoyed reading this, can really feel your frustrations trying to solve it, I hope you continue to work it out. Over the years I've done most of the things you've tried as preventative measures, I have the later version of the N52 lump now with 150k miles and nearly 20 odd track days over the years. The only symptom I share is the occasional lumpy idle which is very slight for me and barely noticeable.

Have you ventured onto Zpost with your problems I see many people really pushing these engines into unknown territory, 300bhp naturally aspirated etc, turbo 400bhp+. They must be getting very intimate with the N52 lump.

 

[propaintballa]

Really enjoyed reading this, can really feel your frustrations trying to solve it, I hope you continue to work it out. Over the years I've done most of the things you've tried as preventative measures, I have the later version of the N52 lump now with 150k miles and nearly 20 odd track days over the years. The only symptom I share is the occasional lumpy idle which is very slight for me and barely noticeable.

Have you ventured onto Zpost with your problems I see many people really pushing these engines into unknown territory, 300bhp naturally aspirated etc, turbo 400bhp+. They must be getting very intimate with the N52 lump.

I am glad my peril is enjoyable! Just kidding, on the bright side it has certainly been a journey on which I have learnt a lot about the car and this engine. In all honesty, I stopped trying to figure it out because of other priorities, so have very little disposable income to throw at the car, so I have just been dealing with it (excluding my last attempt with the CCV). I doubt I will ever solve it, but if I still have it spring next year, I might venture to Z post and have a final punt at it!

Glad to hear your engine has been trouble free. I had the same era N52B30 in my Z4 coupe with way more miles on than my current car and it was an absolute peach. Wish I could have just kept that engine by itself! Haha

 

[mejim707]

Hi, I've been reading through this because I have the exact same issue. I'm getting shudder typically in stop and go traffic. Or if rolling at about 2 mph through a stop then slightly pressing the gas I'll get a heavy jerking shudder. I also get it in all gears if I'm slowing down then need to speed back up. This will also happen after gear shift, let's say from 2 to 3 there will be a vibration before, then a shudder after and some times a hum / vibration in the car. This primarily happens when lightly accelerating and not beating on the car. Hard acceleration results in snappy performance but I'd be beating on it. If I throw the car in sport the issue mostly clears up.

Also, while driving normal, on straight roads slightly pressing the gas to maintain speed I get a 100 to 200 rpm fluctuation where the rpm bounces in those increments unless I press the gas harder or let off a big and it smooths out. If I press the pedal a little more to put load on the engine instead of a quick increase in rpm the engine bogs down dropping a few hundred rpm until I really mash the pedal to get the thing to go.

This is not consistent. For instance the last few days the car has been near perfect. Then today with no changes to weather, driving conditions, vehicle, or fuel the shudder is back full on.

I've done the following;
Replaced coils
Replaced plugs
Replaced both vanos vales with BMW OEM ones - Not cheap! Ran me close to $400!
Replaced both vanos check valves with BMW OEM ones - About $100 for both.
Replaced valve cover PCV.
Tested vanos system and Eccentric Shaft motor and all is working properly according to the scans and tests.
Reset and Relearn of Transmission adaptations.
Tried various injection cleaners.

I've scanned the vehicle extensively with INPA and ISTA and everything looks good. There are no engine or transmission codes in any module either. Even after a rough drive, I check for codes and all systems say the car is perfectly fine.

I don't understand how the car can feel awesome and smooth as silk one day, then the next just feel like crap and be all bogged down. Craziness. I hope someone finally figures this crap out. Team work baby!

 

[propaintballa]

Hi, I've been reading through this because I have the exact same issue. I'm getting shudder typically in stop and go traffic. Or if rolling at about 2 mph through a stop then slightly pressing the gas I'll get a heavy jerking shudder. I also get it in all gears if I'm slowing down then need to speed back up. This will also happen after gear shift, let's say from 2 to 3 there will be a vibration before, then a shudder after and some times a hum / vibration in the car. This primarily happens when lightly accelerating and not beating on the car. Hard acceleration results in snappy performance but I'd be beating on it. If I throw the car in sport the issue mostly clears up.

Also, while driving normal, on straight roads slightly pressing the gas to maintain speed I get a 100 to 200 rpm fluctuation where the rpm bounces in those increments unless I press the gas harder or let off a big and it smooths out. If I press the pedal a little more to put load on the engine instead of a quick increase in rpm the engine bogs down dropping a few hundred rpm until I really mash the pedal to get the thing to go.

This is not consistent. For instance the last few days the car has been near perfect. Then today with no changes to weather, driving conditions, vehicle, or fuel the shudder is back full on.

I've done the following;
Replaced coils
Replaced plugs
Replaced both vanos vales with BMW OEM ones - Not cheap! Ran me close to $400!
Replaced both vanos check valves with BMW OEM ones - About $100 for both.
Replaced valve cover PCV.
Tested vanos system and Eccentric Shaft motor and all is working properly according to the scans and tests.
Reset and Relearn of Transmission adaptations.
Tried various injection cleaners.

I've scanned the vehicle extensively with INPA and ISTA and everything looks good. There are no engine or transmission codes in any module either. Even after a rough drive, I check for codes and all systems say the car is perfectly fine.

I don't understand how the car can feel awesome and smooth as silk one day, then the next just feel like crap and be all bogged down. Craziness. I hope someone finally figures this crap out. Team work baby!

I assume your car is an Auto? What is your mileage and when was your last gearbox service? On the subject of eccentric shafts, have you checked for oil in the eccentric shaft sensor connector?

 

[mejim707]

Thanks for the reply! Yes it’s an automatic and the car has 250k on it. It runs perfectly other than this shuttering issue that comes and goes. There are no codes either other than a few sensors for the defrost and one for the number comfort access antenna. Nothing major.

The transmission has never had a fluid change. At around 120,000 miles I was going to change the fluid and I was told by all of the shops not to do it and I waited too long. They said it had to be done at 100. So after calling a bunch of places I just didn’t do it because they all said don’t. But now I’m reading that apparently ZF says to go ahead and do it anyway. So I really don’t know what to think. But it has not had a fluid change.

I think it’s weird that one day it works perfectly. Then the next day it’s acting up again.

 

[propaintballa]

Thanks for the reply! Yes it’s an automatic and the car has 250k on it. It runs perfectly other than this shuttering issue that comes and goes. There are no codes either other than a few sensors for the defrost and one for the number comfort access antenna. Nothing major.

The transmission has never had a fluid change. At around 120,000 miles I was going to change the fluid and I was told by all of the shops not to do it and I waited too long. They said it had to be done at 100. So after calling a bunch of places I just didn’t do it because they all said don’t. But now I’m reading that apparently ZF says to go ahead and do it anyway. So I really don’t know what to think. But it has not had a fluid change.

I think it’s weird that one day it works perfectly. Then the next day it’s acting up again.

Jesus Christ! 250k on the original gearbox fluid and filter. That would be my first and immediate port of call, new fluid and filter. I could almost bet money on this being your issue. I have seen a number of cases with similar but slightly different symptoms to mine on auto cars, both on this forum and others. Most notably you have issues when slowing down as well as well as RPM changes when moving, which wouldn't really be possible in a manual car. Naturally I take no responsibility if this turns out not to be the problem, but I personally would be servicing my auto box (if I had one) every 50-75k miles. From what I gather, this isn't a particularly difficult job if you're into your DIY and you have the tools necessary to jack the car up so it's level.

 

[propaintballa]

Thanks for the reply! Yes it’s an automatic and the car has 250k on it. It runs perfectly other than this shuttering issue that comes and goes. There are no codes either other than a few sensors for the defrost and one for the number comfort access antenna. Nothing major.

The transmission has never had a fluid change. At around 120,000 miles I was going to change the fluid and I was told by all of the shops not to do it and I waited too long. They said it had to be done at 100. So after calling a bunch of places I just didn’t do it because they all said don’t. But now I’m reading that apparently ZF says to go ahead and do it anyway. So I really don’t know what to think. But it has not had a fluid change.

I think it’s weird that one day it works perfectly. Then the next day it’s acting up again.

Any updates @mejim707 ?

On a personal note, I replaced the oil filler cap on my car because it had been weeping for ages and I finally figured it could only be bad. Weirdly I noticed a definite improvement to driveability, particularly when pulling away from stationary, but still the hesitation is present to varying degrees.

 

[mejim707]

Any updates @mejim707 ?

On a personal note, I replaced the oil filler cap on my car because it had been weeping for ages and I finally figured it could only be bad. Weirdly I noticed a definite improvement to driveability, particularly when pulling away from stationary, but still the hesitation is present to varying degrees.

Hey propaintballa! Yes I've seen in the past that the oil filter and oil viscosity can contribute to performance. I'd imaging that a leak would do the same. These oil filter caps have the basket piece that fails and that'll cause issues as well.

I do have an update actually. 99% of my issues was due to the Bank 1 and 2 sensor 2 / downstream O2 sensors failing silently. No code or anything was thrown including when I scanned with ISTA. Last month the car got REALLY bad. Terrible shaking and jerking then suddenly I get a code. Bank 2 sensor 2 no signal. I jumped right on it, changed the sensor and the car felt beautiful again! I was reading they usually fail around the same time and go figure two days ago I get another code Bank 1 sensor 2 no signal. I changed that one out as well. The car feels awesome!

O2 sensors are a maintenance item so they should be changed occasionally. I've never changed any after 255k and this is the first they've failed. So it wasn't so bad dropping the $300 for two new ones. Still hurt though.

I will be doing the transmission flush still but I need to find the appropriate place to get the kit and exactly all the stuff I'll need. That's a project for Feb.

 

[propaintballa]

Any updates @mejim707 ?

On a personal note, I replaced the oil filler cap on my car because it had been weeping for ages and I finally figured it could only be bad. Weirdly I noticed a definite improvement to driveability, particularly when pulling away from stationary, but still the hesitation is present to varying degrees.

Hey propaintballa! Yes I've seen in the past that the oil filter and oil viscosity can contribute to performance. I'd imaging that a leak would do the same. These oil filter caps have the basket piece that fails and that'll cause issues as well.

I do have an update actually. 99% of my issues was due to the Bank 1 and 2 sensor 2 / downstream O2 sensors failing silently. No code or anything was thrown including when I scanned with ISTA. Last month the car got REALLY bad. Terrible shaking and jerking then suddenly I get a code. Bank 2 sensor 2 no signal. I jumped right on it, changed the sensor and the car felt beautiful again! I was reading they usually fail around the same time and go figure two days ago I get another code Bank 1 sensor 2 no signal. I changed that one out as well. The car feels awesome!

O2 sensors are a maintenance item so they should be changed occasionally. I've never changed any after 255k and this is the first they've failed. So it wasn't so bad dropping the $300 for two new ones. Still hurt though.

I will be doing the transmission flush still but I need to find the appropriate place to get the kit and exactly all the stuff I'll need. That's a project for Feb.

You're right, I went from 5w30 to 5w40 with no difference sadly. Also made sure the filter basket thing you mentioned was still there too, which it was.

I am glad you managed to find your issue! That's actually really interesting because I thought about that for my issues, but the general consensus was that the downstream sensors don't play a huge role, which obviously seems to be incorrect. I replaced my upstream o2 sensors after I unplugged the original ones and the car ran much better, but didn't fix the issues after replacement. Maybe I will look into my post-cat sensors too.

Glad you're looking into getting the gearbox fluids changed, I think that's important if you want to keep the car going even longer!

 

[toobroke4mods]

TL;DR at the bottom, I like detail!

Hey propaintballa,

I've recently been having similar problems to the issues you described on the first page of this thread in my '06 N52B25-powered manual 325i. I don't own a Z4 but I created an account here just because of this thread! I read through the whole thing during a very boring work meeting a few nights ago and wanted, first, to thank you for the in-depth description of the issues you're having, and the continued dedication to updating others on your progress, and second, wanted to tell you about my experience, in case it helps you or anyone else that stumbled on this thread.

This problem developed for me during the cold British winter (nights of negative Celsius, frost in the mornings). At first, it began as a very minor misfire at low RPM when the engine was cold. About a mile down the road, it would be running normally again. Then it slowly got worse, first it misfired for longer, to the extent that it was still not running right by the time I got to work (only 4 miles or so) but would still be OK if I took the long way home (about 15 miles, country roads). Eventually, it got to the point that it would misfire even when it was at full operating temperature.

By this point, it was so bad that the car became undriveable. It would not rev past 2,000 RPM in 2nd+ gear giving me so little power that I struggled to get up some hills in the city. I stopped driving for 2 weeks and relied on lifts. I did a huge amount of Googling and eventually decided it was the CCV (N52K, black engine cover so CCV is built into valve cover) due to the symptoms and because my oil filler cap was pulling huge vacuum (enough to hold the oil filler cap down) when the engine was running. I purchased a part like this on eBay for £20, smashed the old one off the valve cover (check YT for videos) and stuck the new one in with silicon gasket maker: https://vanos-bmw.com/product/11127552281-bmw-valve-cover-repair-kit-n52-n51-n52n-n52k

Unfortunately, upon starting the car, the crankcase was still creating massive vacuum and on a test drive, it performed just as badly. This was on the Thursday just gone.

Following that, I read another thread that mentioned on the N52 engines with Valvetronic, the throttle doesn't actually do anything during normal operation, instead staying fully open, and that power delivery is actually controlled by changing the variable valve lift with Valvetronic. Really sorry, but I can't find the thread this was mentioned in, probably just a related comment on another thread, maybe even this one somewhere lol.

In my further searching, Google brought up a comment from this webpage which described exactly my issue with not going over 2k RPM, so I clicked and read through to find the comment: https://www.pelicanparts.com/BMW/techarticles/BMW-3-Series-E90/FUEL-Valvetronic_Motor_Replacing/FUEL-Valvetronic_Motor_Replacing.htm. Valvetronic again huh?

THEN I found this thread on Bimmerfest which described somewhat similar symptoms and I thought, "what the heck, I have a scanner which can do this, let's give it a go". So, using my Foxwell NT530 with the BMW software, I started a relearn of the Valvetronic values. This takes seconds once you've navigated through the menus for a few minutes. Side note, the NT530 is highly capable and for £150, I think ANY BMW owner who works on their own stuff should have one. It's literally already paid itself off in dealer labor and diagnostic costs.

Following this, I took it out expecting the worst, and the bloody thing only went and ran beautifully! I have it a good jaunt around town to get it up to temp for the first time in 2 weeks or so, then got back home, met one of my mates and took it on a nearby high speed road to run it properly.

I thought this was it and the problem was solved. Unfortunately not. As suspected, there is a reason Valvetronic lost its adaptions in the first place. I suspect there is oil in the eccentric camshaft sensor on top of the valve cover. Bloody typical that I only just put the whole engine cover and cabin air filter assembly back together on Thursday, cos now I need it off again. You Z4 owners don't know how lucky you are to be able to access the whole engine without restriction!

Anyway, there is clearly still a problem so tomorrow (Sunday) I'll get the engine cover off again and check for oil in the eccentric camshaft sensor connector (apparently a common fault if the gasket fails). If there is, unfortunately I believe it will be a valve-cover-off job to replace the sensor and gasket, but at least that should sort my problems. Hope this helps someone and I will update once I've checked the sensor connector.

TL;DR:

Symptoms:

• Engine won't rev above 1.5-2k RPM in 2nd gear+

• Lots of crankcase vacuum

• Uneven idle, perks up and down, almost "throbs", sends small vibrations through car

• Before it became undriveable, would occasionally sound "airy" or "dry" when flooring it to high RPM, oil level fine

Things tried

• VANOS solenoids were replaced <2000 miles ago and swapped positions to test, no fault codes after clearing old ones

• Spark plugs have not been pulled to check them, but I don't think plugs/coils cause this as misfire happened on all cylinders simultaneously and not just on some

• New crankcase ventilation (CCV) valve installed on existing rocker cover

• Running in "open loop" (MAF unplugged) does not improve running

• Oil is still within service interval and at the right level (although maybe should be changed soon)

• Resetting Valvetronic adaptions using Foxwell NT530 with BMW software (THIS WORKS TEMPORARILY)

Next steps

• Next step is checking eccentric camshaft sensor connector for oil, checking Valvetronic motor/camshaft wear if sensor is dry.

Propaintballa, if you don't have a proper BMW specific scanner that can perform service functions, I would highly recommend trying to reset your Valvetronic adaptions to see if this sorts it. I know you have tried replacing the motor, but if the car doesn't know what 0 and 100 percent mean, any number of new motors will not help. You may have already tried this and I just haven't seen it/forgot, apologies if this is the case.

 

[propaintballa]

TL;DR:

Symptoms:

• Engine won't rev above 1.5-2k RPM in 2nd gear+

• Lots of crankcase vacuum

• Uneven idle, perks up and down, almost "throbs", sends small vibrations through car

• Before it became undriveable, would occasionally sound "airy" or "dry" when flooring it to high RPM, oil level fine

Things tried

• VANOS solenoids were replaced <2000 miles ago and swapped positions to test, no fault codes after clearing old ones

• Spark plugs have not been pulled to check them, but I don't think plugs/coils cause this as misfire happened on all cylinders simultaneously and not just on some

• New crankcase ventilation (CCV) valve installed on existing rocker cover

• Running in "open loop" (MAF unplugged) does not improve running

• Oil is still within service interval and at the right level (although maybe should be changed soon)

• Resetting Valvetronic adaptions using Foxwell NT530 with BMW software (THIS WORKS TEMPORARILY)

Next steps

• Next step is checking eccentric camshaft sensor connector for oil, checking Valvetronic motor/camshaft wear if sensor is dry.

Propaintballa, if you don't have a proper BMW specific scanner that can perform service functions, I would highly recommend trying to reset your Valvetronic adaptions to see if this sorts it. I know you have tried replacing the motor, but if the car doesn't know what 0 and 100 percent mean, any number of new motors will not help. You may have already tried this and I just haven't seen it/forgot, apologies if this is the case.

Hey, thanks for your post, I enjoyed reading about your saga! I am intrigued to see how you get on with your eccentric shaft sensor. As for me, thank you for your suggestions, however I did change the valvetronic motor and also relearned adaptions as well with both the replacement and the original. Granted, the replacement was a used part but I would be very surprised if both motors would give me the exact same symptom! I was using INPA for my diagnostics, I also have a small BMW scanner which is good for simple things like fault codes and some other stuff.

Weirdly, I can relate to your "airy/dry" description of symptoms when flooring it. I too had a similar thing whereby the car would almost sound like there was some kind of vacuum leak, which I suppose is still possible.

 

[toobroke4mods]

Hey, thanks for your post, I enjoyed reading about your saga! I am intrigued to see how you get on with your eccentric shaft sensor. As for me, thank you for your suggestions, however I did change the valvetronic motor and also relearned adaptions as well with both the replacement and the original. Granted, the replacement was a used part but I would be very surprised if both motors would give me the exact same symptom! I was using INPA for my diagnostics, I also have a small BMW scanner which is good for simple things like fault codes and some other stuff.

Weirdly, I can relate to your "airy/dry" description of symptoms when flooring it. I too had a similar thing whereby the car would almost sound like there was some kind of vacuum leak, which I suppose is still possible.

Hey, glad to hear back from you

I checked the ESS yesterday, thankfully I hadn't fully bolted down the engine cover so it could still be removed without removing the cabin air filter housing. There is no oil in the ESS sensor or connector, and the contacts are clean. I suspected it might not be this because most people with troublesome eccentric shaft sensors seem to get codes from the DME, but I only get code 2AAB occasionally, which the Foxwell decodes as "variable intake self diagnosis". Not particularly useful because there are so many variables in the intake!

Unfortunately, and weirdly, I tried the Relearn Valvetronic Limits procedure again, and it didn't make much difference on Sunday. It ran badly before and after the calibration! It was intermittently behaving decently, but I've otherwise been limping around the city in 5/6th gear haha.

I've no idea what's up with this thing now. I was relying on oil in the ESS connector which would have been annoying, but at least fixable. I've read something about VANOS non-return valves being clogged and causing similar issues, but why would a Valvetronic recalibration fix the problem on Saturday if it was that? Very weird.

Thinking I might give it a proper oil flush and change to remove the crud in the head, replaced with 5w-40 instead of the current 5w-30 maybe. I'll keep this thread updated with anything else I find!

 

[toobroke4mods]

OK, further update today. I had a quick look at that 2AAB code on my lunch break today, and many of the top results mention DISA. A few mention VANOS, but as I've mostly discounted that as a fault, I'm inclined to think it's more likely to be DISA.

Unfortunately, our British winters mean the sun is setting by the time I get home from work and it's always very cold, so I may not have an opportunity to get at the DISA valves until the weekend. The silver lining is I only have a 2.5 325i and not a 330i, so there is (I believe) only two valves and unlike the 3 stage manifold. I haven't look much into the process yet, but from what I understand, one is very easy to access and the other requires the removal of the whole intake manifold, so if there is a DISA fault, let's just hope it's the easy one!

May not be able to provide an update until the weekend. The boss is off this week so can't sign a day off for me to take a look in the light either. Rotten luck haha

 

[propaintballa]

OK, further update today. I had a quick look at that 2AAB code on my lunch break today, and many of the top results mention DISA. A few mention VANOS, but as I've mostly discounted that as a fault, I'm inclined to think it's more likely to be DISA.

Unfortunately, our British winters mean the sun is setting by the time I get home from work and it's always very cold, so I may not have an opportunity to get at the DISA valves until the weekend. The silver lining is I only have a 2.5 325i and not a 330i, so there is (I believe) only two valves and unlike the 3 stage manifold. I haven't look much into the process yet, but from what I understand, one is very easy to access and the other requires the removal of the whole intake manifold, so if there is a DISA fault, let's just hope it's the easy one!

May not be able to provide an update until the weekend. The boss is off this week so can't sign a day off for me to take a look in the light either. Rotten luck haha

Good developments! Just a correction though, the 3 stage manifold is the one that has two DISA valves, it was the other manifold that only had 1. I am pretty sure the 3 stage is the standard here in the European market, was more the US that only had the single-DISA manifold. Anyway...

As you say, the large one is pretty easy to get out, the small disa is a manifold out job, which is an absolute ball ache. If you're going to look at the small DISA, it is worth replacing the manifold gaskets which are pretty cheap from BMW.

VANOS return valves are also easy and worth checking. Clean them out with some carb/brake cleaner and give them a hard blow to see if they allow any air to pass. Naturally, oil pressure is much higher than you can blow, but still worth checking! The reality is though, if your car has had regular oil changes that they will be fine. Mine were basically spotless!

 

[toobroke4mods]

OK, further update today. I had a quick look at that 2AAB code on my lunch break today, and many of the top results mention DISA. A few mention VANOS, but as I've mostly discounted that as a fault, I'm inclined to think it's more likely to be DISA.

Unfortunately, our British winters mean the sun is setting by the time I get home from work and it's always very cold, so I may not have an opportunity to get at the DISA valves until the weekend. The silver lining is I only have a 2.5 325i and not a 330i, so there is (I believe) only two valves and unlike the 3 stage manifold. I haven't look much into the process yet, but from what I understand, one is very easy to access and the other requires the removal of the whole intake manifold, so if there is a DISA fault, let's just hope it's the easy one!

May not be able to provide an update until the weekend. The boss is off this week so can't sign a day off for me to take a look in the light either. Rotten luck haha

Good developments! Just a correction though, the 3 stage manifold is the one that has two DISA valves, it was the other manifold that only had 1. I am pretty sure the 3 stage is the standard here in the European market, was more the US that only had the single-DISA manifold. Anyway...

As you say, the large one is pretty easy to get out, the small disa is a manifold out job, which is an absolute ball ache. If you're going to look at the small DISA, it is worth replacing the manifold gaskets which are pretty cheap from BMW.

VANOS return valves are also easy and worth checking. Clean them out with some carb/brake cleaner and give them a hard blow to see if they allow any air to pass. Naturally, oil pressure is much higher than you can blow, but still worth checking! The reality is though, if your car has had regular oil changes that they will be fine. Mine were basically spotless!

Thanks for the corrections about the DISA valves! I'm not sure if the 2.5 325i will have the single DISA or not, I figured the 3 stage manifold was only used on the 330i, and single DISA on the 3.0 325i and 2.5. I think I've seen the connector for the second DISA beneath the intake runners, but I'll double check it this weekend.

I've heard the non-return valves can be a pain to get to, requires removal of the wheel liner due to their placement. My motors got full service history and has had oil changes in decent intervals, but I've only owned it since August and it could probably do with a proper flush. I'll try to get those checked out anyway, looks like they just simply unscrew once you've got access.

Thanks for the help, I'll update you after I've checked it out in Saturday!

 

[propaintballa]

OK, further update today. I had a quick look at that 2AAB code on my lunch break today, and many of the top results mention DISA. A few mention VANOS, but as I've mostly discounted that as a fault, I'm inclined to think it's more likely to be DISA.

Unfortunately, our British winters mean the sun is setting by the time I get home from work and it's always very cold, so I may not have an opportunity to get at the DISA valves until the weekend. The silver lining is I only have a 2.5 325i and not a 330i, so there is (I believe) only two valves and unlike the 3 stage manifold. I haven't look much into the process yet, but from what I understand, one is very easy to access and the other requires the removal of the whole intake manifold, so if there is a DISA fault, let's just hope it's the easy one!

May not be able to provide an update until the weekend. The boss is off this week so can't sign a day off for me to take a look in the light either. Rotten luck haha

Good developments! Just a correction though, the 3 stage manifold is the one that has two DISA valves, it was the other manifold that only had 1. I am pretty sure the 3 stage is the standard here in the European market, was more the US that only had the single-DISA manifold. Anyway...

As you say, the large one is pretty easy to get out, the small disa is a manifold out job, which is an absolute ball ache. If you're going to look at the small DISA, it is worth replacing the manifold gaskets which are pretty cheap from BMW.

VANOS return valves are also easy and worth checking. Clean them out with some carb/brake cleaner and give them a hard blow to see if they allow any air to pass. Naturally, oil pressure is much higher than you can blow, but still worth checking! The reality is though, if your car has had regular oil changes that they will be fine. Mine were basically spotless!

Thanks for the corrections about the DISA valves! I'm not sure if the 2.5 325i will have the single DISA or not, I figured the 3 stage manifold was only used on the 330i, and single DISA on the 3.0 325i and 2.5. I think I've seen the connector for the second DISA beneath the intake runners, but I'll double check it this weekend.

I've heard the non-return valves can be a pain to get to, requires removal of the wheel liner due to their placement. My motors got full service history and has had oil changes in decent intervals, but I've only owned it since August and it could probably do with a proper flush. I'll try to get those checked out anyway, looks like they just simply unscrew once you've got access.

Thanks for the help, I'll update you after I've checked it out in Saturday!

So I think that was the case in the American market, but don't think so here. My 2005 2.5 325i has the 3 stage manifold with 2 DISA valves. I believe if you have the single/dual stage or whatever it is, then you would only have the small DISA, which is the hard to get to one. So if you can see a large ish box in the middle/side of your manifold then it is 3 stage.

As for the non-return valves, you can get to them pretty easily without going through the wheel liner. I can't remember if you can see them with the eye or if I had to stick my phone down there, but it is possible. I have done it twice now and not had any issues

Yeah, engine flush is worth doing for the sake of peace of mind. I think I used one of the liqui moly ones in mine. Sadly made no difference