[The Blimp]

Update - 19/06/20 - Major progress

I was looking through potential items that I could add to an FCP Euro order to enhance the value of the postage costs when I noticed that they had genuine BMW branded MAP sensors on sale (to about the same cost as the OEM supplier's non-BMW ones), so I decided to get one as I had read the MAP can impact on idle.

It arrived on Tuesday and I quickly installed it. Noticed an immediate improvement on idle quality. The jerkiness was drastically reduced (almost gone) and the spasmodic vibrations were nowhere near as violent as they had been. I have been driving around for the last few days testing it out and they have not returned. Fuel economy has also improved.

I have not done any follow up testing with INPA or MHD logging yet as I am moving into a larger house over the next fortnight but will do so as soon as I am able and post up any verifiable results here.

Not sure what was wrong with the old sensor but I will try and find out.

I had also needed to replace the boost solenoid late last year after the stock one crapped out so I am not surprised that a new MAP would also improve things. All up I would say the idle has improved in perceivable quality from 70% to 95%. Still the odd vibration here and there but roughs so much smoother. Also feels like there could be better low down torque but cant back that up apart from butt-dyno.

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I thought that the N55 would be a much easier engine to live with after having two N54 powered cars over the years, but I think I was greatly mistaken.

I moved to a N55 a couple of months ago, hoping that the trade off with lower engine power potential against better reliability would be a smarter outcome but it has been a bit of a pain so far. I'm starting this thread to welcome advice and suggestions, but also to document problems and solutions for other owners that might face the same challenges.

Initial purchase
The N55 I picked up was a 10/2010 build with 68,000kms on the clock. It ran fine when I inspected it and had no codes when scanned. Had a full service history but there were a few issues that I could see such as the oil temps reaching 120-125c and the battery not being coded to the car.

I immediately changed the oil and filter. In hindsight I wish I had run a cleaner additive first such as the Liqui-Moly detox but might do that in the next 1,000kms (I've put 4,000kms on the car so far).

The oil change saw the oil temps never go above 110c, so its likely that the previous oil had been there for some time (too long).

I coded the battery to the car as it was giving the increased battery discharge' code at start up. The battery was replaced in mid-2016 so Im not sure there would be any ill effects of not having it properly coded for so long.

The PCV vent hose had cracked and I had a replacement one that I got with a secondhand intake system off eBay ($50).

I also replaced the ignition coils with Delphi coils from FCP Euro, as well as fresh Bosch branded plugs (ZR5TPP33S) that I got on special from supercheap. Engine ran fine after this until...

Limp Mode Event #1 - Resolved
Not long after changing oil, plugs and coils, I was hit with a half-engine limp mode. Power was indeed reduced and I did literally limp it home. Upon reading the codes:

2C56 - Boost Control, Pressure Too High
2C58 - Boost Pressure Deactivation
36C9 - Internal DME Fault

Researching the issue it appeared that the culprit was a dead/dying boost solenoid. This was replaced with a Pierburg branded version and all was running great again - in fact better than before.

Idle issues - Ongoing
The more familiar I got with the car, I started to notice that there is a rough vibration at idle, which will get worse if the AC is engaged. It can easily be felt through the steering wheel and pedals, like a fish pulling on a line.

It will also idle-hunt when stopping at the lights or putting into park.

I inspected the engine bay and noticed that the tensioner pulley was moving quite a lot. So I replaced it with a new one. which reduced the movement but didnt have any impact on the idle. I also inspected the crank pulley/harmonic balancer/vibration damper and other pulleys and couldn't see any issues. There isn't any apparent wobble.

Upon researching this issue further I read that the earlier N55s (late 09 to 2011) had a similar issue being caused by an early DME software version. Updating to the latest DME software can potentially resolve the idle problems, which is the next course of action.

If updating the DME doesn't improve this, other culprits might be the VANOS solenoids being dirty/dying (about $450 to replace both), or the PCV system failing and there being an internal vacuum leak (apparently not uncommon with the integrated N55 PCV) - an expensive item to replace.

Still sorting this one out

Limp Mode Event #2 - ??
After driving with some gusto and then parking for a little while, upon restarting the engine it immediately entered a half-engine limp home mode. After pulling over and scanning the DME it was the following:

2BF8 - Rail Pressure Sensor, signal; Permanently stuck
2C01 - High fuel pressure, Pressure too low.

I cleared the codes and they haven't yet returned but I haven't actually given the spurs to the car since so I am not sure if it will return.

Researching this issue it could be (hopefully) just the rail pressure sensor needing to be replaced (which I have ordered from FCP Euro).

If it isn't the sensor, then I guess the HPFP will be the next culprit but I still haven't had any classic long cranks or anything like that so I'm leaning towards the sensor being on its way out.

Fuel Economy - Ongoing
When I first purchased the vehicle I didnt notice any issues with the fuel consumption, however since I have been diagnosing issues I have notice that consumption is up around 20l/100km.

I looked for a vacuum leak but couldn't see anything out of place. I inspected the MAF sensor and noticed it was quite dirty and there was some oxidation on the metal tab and resistor, so I replaced it with a VDO branded one (again from FCP Euro) hoping that it would resolve the issue (and maybe the idle problem too). Alas this did not improve anything and I'm back to the drawing board on this one - it could be multiple things. I am trying to get ISTA to run on my laptop and so will hopefully get to run some proper diagnostics.

[juld0zer]

Firstly - unless your pockets are deep, stop firing the parts cannon and invest in some diagnosis.

The idle issue with the AC on or coming to a halt is a well known issue and I am going to assume yours is a DCT as I've not heard of it affecting manual cars. edit: Missed the bit about putting it into park. The software update addresses this issue. There are several threads on the forum about this including one very detailed one which details one owner's battle.

What was the service history like? It sounds like the previous owner was never fussed about it or the car rarely saw a dealership. Has it had all the recalls done? (junction box cable, driver airbag, VANOS?).

Is there any tune or piggyback installed?
20L/100km is ridiculous. Mine averaged around 11.5. Still crap for a 3L motor.

You should also reset the adaptations after installing a new MAF sensor.

[The Blimp]

Update: flashed the DME with latest N55 software. It improved its behaviour when driving and idling but still has something (or things) wrong.

Got inpa to work but as there is only a German language version for n55 it’s hard to use. Did a rough running test and it appeared all was within tolerances at idle (though I still can’t find definitive info on what the figures mean and how the test should be performed - which makes diagnosis difficult).

Idle


When I increased revs to ~3000rpm+ the thresholds were exceeded on cylinders 1, 3 and 4.


I posted this over in the main N55 sub forum and the Oz FB page for advice as I am unsure what these values mean.

I swapped coils between cyl. 2 and 3 but it made no change to the values in inpa.

I am leaning towards the injectors being clapped out as the plugs and coils and basically new. No current fault codes.

[The Blimp]

Originally Posted by juld0zer

Firstly - unless your pockets are deep, stop firing the parts cannon and invest in some diagnosis.

The idle issue with the AC on or coming to a halt is a well known issue and I am going to assume yours is a DCT as I've not heard of it affecting manual cars. edit: Missed the bit about putting it into park. The software update addresses this issue. There are several threads on the forum about this including one very detailed one which details one owner's battle.

What was the service history like? It sounds like the previous owner was never fussed about it or the car rarely saw a dealership. Has it had all the recalls done? (junction box cable, driver airbag, VANOS?).

Is there any tune or piggyback installed?
20L/100km is ridiculous. Mine averaged around 11.5. Still crap for a 3L motor.

You should also reset the adaptations after installing a new MAF sensor.

Thanks for your reply

All recall work was done prior to my purchasing of the car. It has been serviced by bmw dealers up to 40k km and then by a euro specialist in eastern suburbs of Sydney - however I’m sure they did the standard bmw service intervals.

No jb4 is attached and doubt previous owners had one installed (but can never be sure).

Without specific codes it’s hard to properly diagnose what is happening. I think the dme is ignoring rough running as inpa testing appears to show that things aren’t quite right.

I don’t want to spend money if I don’t need to but I think it is obviously a hardware problem.

[The Blimp]

Ok, I’ve done some more research and discovered that I shouldn’t have used the throttle during the rough running test (not that there are instructions for this stuff - at least not easily accessible).

It measures idle performance and I’m (guessing) that cylinders 3 and 4 are the most efficient when given revs as they are right behind the throttle body.

Anyway, any result at idle that is beyond -.5 means the injector is toast and is leaking at idle. So from my previous screenshot I can see that cylinder 1 is in excess of this and must have its injector replaced.

That’s some progress anyway

[Socket]

Nice work mate... diagnosis is always the hardest task

[juld0zer]

If you have access to ISTA, try an adaptations reset. I don't recommend doing it in INPA because it can cause some cold start issues on some DMEs.

For the fuel pressure issue you need to monitor the target vs actual pressures at idle and under load. Keep in mind that unlike the N54, this motor has no LP fuel sensor so the rail pressure sensor has sufficient resolution to monitor the low pressure system also.

What other fault codes do you have?

[N55Jamaican]

[The Blimp]

I've managed to do a bit of diagnosis work with logs and INPA functions.

Fuel pressure is never below 700 and isnt a problem at idle or at WOT. Boost is fine and WGDC is within spec.

Rough running analysis shows that all cylinders are way out of tolerances over a 10 second period when the engine is at operating temp, most dip between -2.0 to +2.0 but cylinder 4 went over 4.0. The DME cannot balance them. LTFT and STFT show that the DME is always pulling fuel but for some reason no CEL is being raised. O2 sensor voltage is always around 1.45v (2.0v is ideal) indicating the rich condition but still no code, which is worrying in itself.

Either the plugs, coils or injectors are defective. Plugs and coils are new, and the symptoms existed prior to replacing them so that really leaves injectors. I have arranged to get them all replaced but it wont be until early January. So until then I am not sure if I should drive the car normally or leave it until they can be replaced.

No codes makes me think that the issue is within tolerance for BMW but the stories of ruined N55s due to injector leaks scares me (I have read so many threads on here about this trying to figure all this out).

The oil in the motor is 3,200kms old and with leaking injectors I am suspicious that it will be diluted with fuel. So I plan to change it asap but not sure if its safe to drive without risking damage.

[The Blimp]

I managed to pick up a genuine BMW VANOS solenoid for $200 shipped a few weeks back.

I was interested to test whether replacing the intake solenoid would have any affect. So on the weekend I swapped it out and it indeed improved the situation a great deal. I was contemplating removing and cleaning the exhaust one but will just replace it with a new one down the track.

Before there was surging idle for a second or two, between 600 to 900rpm when shifting from P to R or D, coming to a stop at lights, and whenever turning the wheel full lock. This is now gone completely. Updating the DME and changing the VANOS has made a big impact, however the shaking from the leaking injector(s) is still present of course.

Fuel economy has also improved since the solenoid was changed. From getting up to 20l/100km down to 15l with about 200km of the same driving style.

Once I get this sorted I can finally get around to mods and tuning, which I had hoped to have already done by now.

[BSG335]

Originally Posted by The Blimp

I managed to pick up a genuine BMW VANOS solenoid for $200 shipped a few weeks back.

I was interested to test whether replacing the intake solenoid would have any affect. So on the weekend I swapped it out and it indeed improved the situation a great deal. I was contemplating removing and cleaning the exhaust one but will just replace it with a new one down the track.

Before there was surging idle for a second or two, between 600 to 900rpm when shifting from P to R or D, coming to a stop at lights, and whenever turning the wheel full lock. This is now gone completely. Updating the DME and changing the VANOS has made a big impact, however the shaking from the leaking injector(s) is still present of course.

Fuel economy has also improved since the solenoid was changed. From getting up to 20l/100km down to 15l with about 200km of the same driving style.

Once I get this sorted I can finally get around to mods and tuning, which I had hoped to have already done by now.

Been following your thread out of interest... this is a great breakthrough!

[DR-JEKL]

Back when you were in the game with your N54 the N55 was largely deemed more reliable due to being newer and BMW had redesigned quite a few things differently but alas now they're older and have a few kays on them they also suffer from quite a few reliability issues and alike the N54, the N55 has a few inherent design weaknesses (thankfully wastegate rattle isnt one of them!)

Did you screen your vin # to ensure it has had the vanos bolt recall done?

https://www.productsafety.gov.au/rec...09-2012-series

[The Blimp]

Originally Posted by DR-JEKL

Back when you were in the game with your N54 the N55 was largely deemed more reliable due to being newer and BMW had redesigned quite a few things differently but alas now they're older and have a few kays on them they also suffer from quite a few reliability issues and alike the N54, the N55 has a few inherent design weaknesses (thankfully wastegate rattle isnt one of them!)

Did you screen your vin # to ensure it has had the vanos bolt recall done?

https://www.productsafety.gov.au/rec...09-2012-series

Yes, checked the recalls before purchasing it - all had been done.

If I had the choice again I probably would go with an N54 again, but learning about this engine is interesting.

[The Blimp]

Correction

Perhaps others on here already knew this but my previous post stating that the lambda voltage of 2.0v is ideal is actually correct for the n54, but not for the n55.

This is because the other N series 6 cylinders n52,53 and 54 use Siemens dme, with the n55 using Bosch. Apparently Bosch has an ideal lambda value of 1.5v, which means my issues aren’t quite as bad as initially suspected.

My lambda readings were between 1.396 and 1.475v over a 30 second period at idle, which is only 2-7% under the ideal (much better than the ~30% I thought before). So it’s rich, but not that rich.

So I am now assuming that no codes are coming up as it’s not that extreme, though LTFTs show that the dme is pulling 25% fuel at times which I thought would definitely throw a code.

Anyway, I thought it best to correct myself as I go along. I’m not a mechanic so it’s all a matter of learning from scratch for me. That said, I had taken the car to 2 workshops (one general and one euro specific) and neither could work it out. I think it’s common these days for fault codes to do 90% of the work, so no codes = no idea.

[The Blimp]

Purchased another VANOS solenoid to replace the exhaust bank. Got it from Schmiedmann, and it took basically no time at all to arrive (purchased 2:33pm on Friday and it arrived at 2:00pm today). Really impressed with Schmiedmann these days, use the Danish Kroner and its not a bad conversion.

Anyway, swapped it in just now and reset the VANOS adaptations. Idle is much improved over just the replaced intake solenoid, and miles better than when I bought it. Still having the leaking injector issues but not long to go for those.

[The Blimp]

Update - Feb 2020


I asked the workshop I usually use to verify my diagnosis for injector issues - though they came back stating that they couldn't detect a problem and therefore couldn't suggest replacing them.

This made me somewhat embarrassed as I was sure they needed to go from the work I had done so far to pinpoint the likely culprit.

So being back at square one left me scratching my head what to do. I followed some advice I have received online and ran a program called ScanMaster ELM to run a mode 6 report. I purchased a cheap ELM interface and loaded the software after a moderate drive. Sure enough, there was a misfire detected in Cyl. 4. No codes were thrown but it was something to now move on.

I decided to start from scratch and replace the plug (they are cheap enough), swap a coil and see if it made any difference. Before I did this I had to go for another moderate drive and decided to rescan before changing the plugs. Now there were 2 misfires in Cyl, 4 and now 5.

I changed the plug in cyl. 4 and swapped a coil, not expecting any change, and restarted the scanning. Engine ran the same as before and the misfire was still present.

The likely culprits have to be either injectors on their way out or some other mechanical damage with valves or something else more severe that would be beyond my desire to fix.

I am going to pickup two Bosch injectors from FCP and replace those in cyl. 4 and 5 as a start - with fingers crossed it fixes or at least greatly improves the situation.

This is a pic of what the plug i replaced looked like after less than 5k kms. I am not sure if that is oil splashed onto the top or fuel has washed onto it. Any thoughts??

[vtl]

What diagnostics did they do on the injectors?

If you suspect a leak then they should be tested.

I would suggest removing all of the injectors, and flipping the fuel hardlines upside down, then remount the fuel injectors back onto the fuel hard lines. What you should end up with is all 6 fuel injectors connected to the fuel lines, but pointing upwards.

Remove all injector electrical connectors and give it a few cranks to build rail pressure (the cranking engine will build pressure in the mechanical HPFP). Keep a small clear bottle under each fuel injector and look for leaks while the car is off and sitting.

[The Blimp]

Originally Posted by vtl

What diagnostics did they do on the injectors?

If you suspect a leak then they should be tested.

I would suggest removing all of the injectors, and flipping the fuel hardlines upside down, then remount the fuel injectors back onto the fuel hard lines. What you should end up with is all 6 fuel injectors connected to the fuel lines, but pointing upwards.

Remove all injector electrical connectors and give it a few cranks to build rail pressure (the cranking engine will build pressure in the mechanical HPFP). Keep a small clear bottle under each fuel injector and look for leaks while the car is off and sitting.

I am not sure what they did to refute the need for changing injectors, I doubt it was anything more than check error codes, and as there was none they figured all was well.

I am noticing that a lot of places will only react to error codes.

Anyway, I like your suggestion however I am sure I would make a mess of it and cause further issues. I think the N55 injectors are cheap enough ($150) to just replace them.

[juld0zer]

Originally Posted by The Blimp

I managed to pick up a genuine BMW VANOS solenoid for $200 shipped a few weeks back.

I was interested to test whether replacing the intake solenoid would have any affect. So on the weekend I swapped it out and it indeed improved the situation a great deal. I was contemplating removing and cleaning the exhaust one but will just replace it with a new one down the track.

Before there was surging idle for a second or two, between 600 to 900rpm when shifting from P to R or D, coming to a stop at lights, and whenever turning the wheel full lock. This is now gone completely. Updating the DME and changing the VANOS has made a big impact, however the shaking from the leaking injector(s) is still present of course.

Fuel economy has also improved since the solenoid was changed. From getting up to 20l/100km down to 15l with about 200km of the same driving style.

Once I get this sorted I can finally get around to mods and tuning, which I had hoped to have already done by now.

Variable valve timing directly controls the valve overlap so a duff solenoid or two could definitely cause the symptoms you experienced

[The Blimp]

Idle issues - Ongoing

This will likely be long-winded and boring but just following up in case anyone with a N55 has similar issues wants this info down the track.

Still experiencing a fairly rubbish idle, mostly when cold but occasionally when warm too.

Have done a fair bit of diagnosis, troubleshooting and research and hopefully have made some headway into potential fixes.

Looking at the rough running values in greater detail and over a longer term, I have determined that cylinders 1, 2 and 5 are problematic and potentially causing the rough idle. Even looking back at the screen shots I posted back in March (which I haven't looked at for ages) I can see the issue then as well.

Running the engine at idle for 3 mins and then logging values for each cylinder, (done over 20+ times) it has consistently shown 1, 2 and 5 to record more extreme values (+/-) than 3, 4 and 6. BMW states that these rough run values are from the crank sensor detecting differences in crank/idle speed based on the performance of each cylinder. The rough idle is not constant but a jerky-ness that is irregular and without rhythm. It is worth reiterating that there are no error codes recorded from this rough idle and it doesnt negatively impact the drivability of the car - it just annoys me and I am sure it cant be good for the engine in the long term.

Cylinders 1, 2 and 5 have recorded peak rough run values as extreme as -5.3 and +5.7 during idle, whereas 3, 4 and 6 normally will not go as far as -/+2.5 and mostly stay closer to with -/+1.

BMW state that the factors contributing to rough run values like this are:
- deviation of the fuel injection rate, mixture deviation (faulty injectors)
- different cylinder charge (e.g. coking of intake port, excess air)
- different compression, poor compression
- poor combustion (spark plug, ignition coil)
- unequal charge of cylinder banks (exhaust turbocharger)


With the above in mind, I have already changed the coils and plugs with new ones, and even changed the plugs on 1, 2 and 5 multiple times with Bosch and BMW branded plugs with no improvement.

Carbon build up is reportedly less of an issue for N55 so I am discounting that at the moment.

I have 2 new Bosch injectors that I intend to install this weekend in cylinders 1 and 2. If the rough running in these cylinders improves, then I will replace cylinder 5 as well.

Compression was tested at the time of purchase and the report I received had them consistent and within spec. However if the injectors dont fix it I will redo the test and see for myself.


Limp Mode Event #2

I replaced the rail pressure sensor and there have been no further issues with this error.

Comfort Access

My car came with a whole bunch of options that I didnt particularly want, such as comfort access. It has played up consistently since I bought it, with it working sometimes and then not. It also appears to affect the regular keyfob activity and it takes sometimes up to 5 to 10 presses of the key for it do anything.

I have narrowed it down to the passenger door handle, which rarely worked initially and now not at all. It requires replacing the entire handle and I have ordered one from schmiedmann. I am unsure if it comes pre-painted but fingers crossed it does.

Removal and install looks simple so hoping that once it arrives and installed it should improve the locking and unlocking of the car dramatically.

[E92only]

I am looking forward to reading your update on the injectors. Hopefully that will get rid of the rough idles. Good luck and thank you for your update.

[The Blimp]

I replaced the injector for cylinder 1 this morning and unfortunately there was no improvement. Whether it might be an issue with the other two cylinders (2 and 5) I dont know but as there was no improvement from the INPA rough running values of cylinder 1 I am assuming the idle issue is not injector related.

The old injector didnt look too bad but did have some carbon deposits - though I imagine after 10 years there would be.



Now I am thinking it is either LPFP or HPFP related. I previously discounted these as the inpa values showed issues with 3 cylinders and I assume a fuel supply issue would affect all 6 evenly but perhaps not the case. I will start monitoring the fuel pressure more closely to see if it is a problem.

As a recap, the idle feels like the car is about to spin a rod or something. I sputters and jerks violently in an inconsistent manner. It is worse when cold but doesnt entirely go away even when warmed up.

So far I have replaced/checked:

Spark plugs - Replaced with Bosch. Also changed out 1, 2 and 5 for BMW branded plugs just inc case - No fix.
Coils - Replaced with Delphi. No change.
VANOS solenoids - changed both with BMW solenoids. Improved running of the car but no fix for the idle.
Vacuum lines - No effect.
Crankcase vent hose - replaced as existing one was cracked. No discernible improvement.
Rail pressure sensor - Replaced due to previously limp mode and code. No impact on idle.
Valvetronics Gasket - Noticed oil leaking from gasket so replaced with OEM gasket. No change.

Further things to check/try:

Battery - is a 5 year old bosch. Wasnt coded to the car properly and often got the increased discharge warning upon getting in of a morning. Thinking of replacing with a new Varta G14. Voltage read via MHD is around 11.7v so might be getting too old.
HPFP - havent had any long cranks etc. but have had a weird rail pressure code and resulting limp mode. ~$2000 to replace so not keen on that just yet.
LPFP - have read others with a bad idle on a N55 resolving it with a new LPFP. Will monitor fuel more closely to see.
Valve cover - Have also heard about the problems of the valve cover as it has the PCV etc. in built into it. It could be leaking and causing issues and not throw any codes.