N52 hesitation, stuttering, jerking, surging etc

[propaintballa]

Yeah, I'm about there with you on that. I'm thinking some kind of oil filling syringe and a cigar is where I'm gonna go.

That's interesting to know in regards to CCV. When I take the oil cap off, there's obviously vacuum there, but the car doesn't try to martyr itself. I think changing the PCV is on the list, but given I've got an N52K it'd be a whole new rocker cover, and right now I can't really be arsed. Nor do I want to shell out £2-300 on the part.

I'm still sort of on the fence, considering whether I actually invest the money and try to fix it or go and part-ex it for something else currently. I think the noise on mine has now morphed into some kind of rattle and 'whoosh' noise between 1500-2500 rpm. Research is leading me to suspect the small DISA.

Yet more fun...

Exactly, that seems to circumvent the need for a pump and a standalone smoke container. That sucks with regard to the CCV. The bonus is, although it's expensive, it's certainly a lot easier to change than on the earlier N52! I've seen something like this for your application which might work: https://www.ebay.co.uk/itm/11127552281- ... 2189766625
I suppose it depends on whether the PCV related bits in the valve cover are blocked and such.

Urm, if I was in your position again, I'd probably sell the car, although I'd struggle to find a suitable replacement. Obviously I thought each time I fixed something, it was going to be the fix of all fixes, and I'm still trying to track this s**t down! Rattle and whoosh is certainly odd, I think you're on the right lines with the small DISA :/

Propaintballa - I came up with a theory of false traction control intervention (throttle opening restricted and injection reduced) but I would have expected the skid light to be flashing at the same time. A few days later, the theory was proven false when the juddering returned and this time it is the worst it has ever been.

Pulled and inspected all NGK spark plugs which were fitted in January, nothing really stood out. Fitted another 6 donor coils from a known good set. Even replacing the bloody tank vent valve made no change to the juddering or the negative long term fuel trims. So i'm down $200. I also made a ground strap from the rocker cover to the strut tower as the existing one is corroded. No difference.

Compared actual vs setpoint MAF at idle, 1200 and 2000rpm and it was acceptable.
Did the same with VANOS, Valvetronic eccentric shaft position, throttle body and gas pedal, all was acceptable. I didn't scope anything, so there is still a chance of a high frequency jittery signal. This was all done using values in INPA which has a somewhat slow refresh rate.

I did make a discovery that turning on the AC restored acceleration and significantly reduced the judder around 1400-1900rpm. The flat spot is significantly reduced. I can induce the juddering by turning off the AC. On my Scanguage, I am currently monitoring load, throttle position, ignition timing and intake air temp. When the judder occurs, timing is being retarded. When the flatspot peaks, load is 99 and timing is very close to zero (TDC) or negative at the worst (after TDC). Is this a sign of false knock detection?

I have bit the bullet and ordered a DMF and clutch kit......

Interesting findings, and odd that your A/C being on reduced the symptoms, mine stay the same. The most interesting though is your observation of the timing, which fits in part with my thoughts on this. Not that I've experienced a proven example of this, but for me, the judder feels like an engine that is not timed correctly. It feels like I am keeping the pedal at the same position but gradually the car slows down as it's juddering. I also feel like my rough idle would be characteristic of engine knock, as it's not a consistent misfire, but more like a shiver.

The sick thing is, this could still be several things. It could be the absolute nightmare scenario of cam bearing ledge wear affecting oil pressure that in turn means the timing is incorrect for the engine speed. I think this could still be a factor, even if performance in the higher rev range is fine due to higher oil pressure? I don't know :/ Seeing as that's quite rare I feel like logically, based on fuel trims being quite far out, that this is a fuel/air metering issue. So MAF, MAP, Knock, 02 sensors or vacuum leak. I'd lean more towards a sensor issue seeing as we have very similar symptoms and the range in which it occurs.

I believe BMW rate the 02 sensors for 100k miles and my car is knocking on the door of that figure... The problem is, they are expensive, and there are 4 of them... The other thing is the cam position sensors. The problem I have is that usually when these kind of issues occur, there are codes, hell, there are usually codes for vacuum leaks causing lean conditions and stuff, but nothing here!

As for your DMF and clutch... I'd be interested to see what happens here and whether actually this weird misfire-type behaviour is due to some weird flywheel imbalance. Probably clutching (lol) at straws here.

[ph001]

I think changing the PCV is on the list, but given I've got an N52K it'd be a whole new rocker cover, and right now I can't really be arsed. Nor do I want to shell out £2-300 on the part.

The ccv is serviceable on the n52k.... see here:
viewtopic.php?f=2&t=105709&hilit=Ccv&start=45

[juld0zer]

From your symptoms, I'd say your cause is not the same as mine. I don't think it is a base valve timing issue but perhaps VANOS? When your motor judders and the car slows down despite the same pedal poaition, that is the ignition timing being retarded. It might be worth getting one of those ebay OBD dongles and a suitable app for your phone to watch some basic live data to verify. But that is what mine does. Mashing the pedal further results in a big fat frown. Knock (pinging) usually occurs under load and not idle though.

To diagnose the cam bearing ledge electronically, you'd need something that can access the BMW specific live data from the DME. A basic scanner probably won't show what you need. INPA will do it. This fault usually sets VANOS adjustment error codes and watching the live data of actual vs setpoint angles will give you a good idea of what's happening inside.

I dare say the flywheel issue may just be exacerbated by the actual cause which I may have stumbled across this afternoon.

Does your engine have one of those noisemaker boxes near the firewall?

[propaintballa]

From your symptoms, I'd say your cause is not the same as mine. I don't think it is a base valve timing issue but perhaps VANOS? When your motor judders and the car slows down despite the same pedal poaition, that is the ignition timing being retarded. It might be worth getting one of those ebay OBD dongles and a suitable app for your phone to watch some basic live data to verify. But that is what mine does. Mashing the pedal further results in a big fat frown. Knock (pinging) usually occurs under load and not idle though.

To diagnose the cam bearing ledge electronically, you'd need something that can access the BMW specific live data from the DME. A basic scanner probably won't show what you need. INPA will do it. This fault usually sets VANOS adjustment error codes and watching the live data of actual vs setpoint angles will give you a good idea of what's happening inside.

I dare say the flywheel issue may just be exacerbated by the actual cause which I may have stumbled across this afternoon.

Does your engine have one of those noisemaker boxes near the firewall?

I have to admit, I have problems with this car and the generic readers. I've got an ELM327 bluetooth adapter, but the data it can read is limited to the point where I can only watch the pre-cat o2 sensors and not post-cat. I have a BMW specific standalone reader which is good for codes and some other bits, but again, pretty limited, usually in the same ways. I have INPA with the cable, but in recent weeks I have had problems with something crashing which occurs usually after only a few minutes, if that.

What live data would you look at the determine whether the ignition timing is changing? I haven't seen anything of the sort on the couple of apps I have (Torque lite and "Car scanner"). I have screenshots on an earlier page of this thread of my VANOS screen from INPA.

Yeah that's the thing, I am pretty certain I need a/new engine mount/s, which makes the issue feel worse, but certainly wouldn't solve the problem. Mine doesn't have the noise box thing like on the Z4... Do you think you have a vacuum leak there?

[juld0zer]

With the ELM adapters, I believe it comes down to what your software can access from the DME. I don't have one so INPA (in German) and Scanguage is all I have. INPA can display stuff that ISTA can't, or at least it will be easier to see. Ideally you'd want to be able to safely drive and watch the data so an assistant may be required to either drive or watch the data.

Pre cat sensors are more important than post cat for the purposes of irregular running diagnosis. They are the ones which control the air/fuel mix. A healthy cat will always produce a good, stable reading at the post cat sensors.

The PID you want may be under ignition advance or something to that effect. In ISTA it is under spark advance in the DME control unit functions. In INPA it is in the SAE J1979 tab, at the bottom of the left column "Zundzeitpunkt zylinder 1".

You'd also want to be monitoring load versus spark advance. Once the load is 99%, the DME stops increasing fuel and the flat spot starts, timing gets pulled and eventually goes to 0* advance and possibly retard further. I'm not sure what load I am seeing on the Scanguage (calculated or absolute) but it seems to reference air intake/manifold vacuum - see this link for more clarification: http://obdcon.sourceforge.net/2010/06/a ... oad-value/

I've not smoke tested my car as it does not feel like an unmetered air problem. The reason I asked about the noise maker box is because I started to look into false knocking/pinging. The noise maker is on the intake side of the block, which is the side where the two knock sensors are mountes. Thumping the airbox would cause the trumpet end to rattle loudly so i yanked it off and guess what? No more total flat spot! I am proposing that our engine must be producing a certain vibration in the 1400-1900rpm range that will shake anything loose and create a noise that is mistaken by the knock sensors.

The plastic coolant crossover pipe on top of the radiator also rattles when i thump the Y snorkel, as does the BMW ornamental cover on the intake manifold. I've isolated them using high density foam. So far, so good. AC is off, DTC is not on (regular DSC enabled), tyre pressures set to mimic original rolling radius of the original rim/tyre combo.

[propaintballa]

It's actually the pre-cat sensors I can't see, weirdly, but can see them in INPA and they look okay. Was having issues with INPA recently but managed to sort it and check some stuff again. Did another VVT relearn and that kind of thing. Couldn't really see anything indicative of a problem when the hesitation happens apart from some pretty all over the place short term fuel trims on occasion, nothing concrete.

Some better news though. I managed to construct a ghetto vacuum tester which has lead me to a small vacuum leak at the valvetronic motor. I had a feeling this needed to be replaced anyway, as although there is no oil coming out of it, per se, it has some residue around it. I have no idea whether this size leak is large enough to cause the issues I am having, but I suppose the only way to find out is to replace it. Other good news is that I couldn't seem to see any other leaks.

IMG_20190603_134146.jpg (258.77 KiB) Viewed 2615 times

[Capa]

That is the most enjoyably hood smoke tester I've seen in a while. This is definitely something I need to do.

[propaintballa]

That is the most enjoyably hood smoke tester I've seen in a while. This is definitely something I need to do.

I'm glad you approve I've ordered a new VVT motor gasket for the grand total of about 9 quid from the local dealer, should get it and install it wednesday if all else goes to plan. Is this going to put an end to my chapter in this thread? I'm not going to hold my breath, put it that way!

[Capa]

I feel like there's some kinda smoke, breath related pun there. Particularly given the fat assed doob you appear to have rolled. (:

Lazy as I am, don't suppose you have any links for the pump you've got there?

[propaintballa]

I feel like there's some kinda smoke, breath related pun there. Particularly given the fat assed doob you appear to have rolled. (:

Lazy as I am, don't suppose you have any links for the pump you've got there?

At this point, I don't want to ruin the whole thing for you, but I also don't want to lie to you. Whilst I would love to take credit for said fat doob, it was a merely a dank edit because I forgot to take a picture the poorboy-special with the actual smoke source installed. Instead, I used the cheapest cigars I could find

As for the pump, it can be found here: https://www.amazon.co.uk/Am-Tech-S1495- ... way&sr=8-1

It doesn't get great reviews, but for my street masterpiece, it was fine! Weirdly, it was actually a hissing/bubbling noise from the VVT motor that put me on to the leak before I saw the smoke.

[Capa]

A man after my own heart, haha. Thanks for the link. I've ordered up one of them bad boys, and some gloves.

Come saturday it'll be a trip to the cornershop to find some of the dirtiest smokes I can lay my hands on.

[ph001]

So what's the procedure for doing the smoke test - doesn't all the gas just pass straight out through the exhaust on the N52 or are they all closed with ignition off?

[propaintballa]

A man after my own heart, haha. Thanks for the link. I've ordered up one of them bad boys, and some gloves.

Come saturday it'll be a trip to the cornershop to find some of the dirtiest smokes I can lay my hands on.

Can't wait for your whip to blaze it too. Post back with results!

So what's the procedure for doing the smoke test - doesn't all the gas just pass straight out through the exhaust on the N52 or are they all closed with ignition off?

This was something I wondered before doing it. Basically I just put a glove over the intake pipe, cut a little hole in the finger, inserted my pipe then taped it up as best I could. Initially I pumped it without any smoke to see if it would hold pressure for the same reason you have suggested. It held pressure, so I tried it with the ignition on to make sure the throttle plate was open and it still held pressure. From this I can assume that the inlet/exhaust valves are closed when the engine isn't being cranked. I appreciate that isn't a very eloquent explanation, but it seemed to achieve what I set out to. Smoke and pressure was lost when opening the oil filler cap during the process. I did check the exhaust when I started the car after I had been smoking it, and I couldn't smell or see any of the cigar smoke. It's possible that the general fumes made this impossible or I just wasn't quick enough to the back of the car though.

[juld0zer]

The smoke would just fill the intake manifold, then the crankcase via the oil separator system (I believe), via the rocker cover. Some will enter the cylinder/s but it would be negligible.

I may have a conclusion to my woes and it was fixed with the almighty INPA. The function is not available in ISTA/D.
In the Adaptions menu of INPA, one of them is "gelernte Varienten" (option F7). This deletes the learnt variants coding in the DME (loosely translated from German). Let the car go to sleep (lock vehicle for 5 mins), then all should be good.

However, you must ensure everything is ship shape as in all existing issues, leaks, faulty solenoids, faulty coils, aged plugs etc are all rectified first.

One thing I also noticed is my coolant temp no longer swings wildly, where it used to simulate an intermittent stuck open thermostat (it would randomly cycle down to <80*c). There is a chap on the American E90 forum that describes this peculiar behaviour in detail and a lot of 330i E90 owners described the same symptoms which led to misleading diagnosis resulting in unnecessary replacement of the thermostat and coolant pump (although these are known to fail). From this experience I can say that this is simply a symptom of the illness if you know your thermostat and coolant pump are healthy/recently replaced. I am not sure if an engine overheat scenario triggers a permanent mode in the DME because my engine did overheat once due to a failed coolant pump (red symbol on the cluster, coolant boiled out of the expansion tank). Others will have to chime in with their vehicle history to see if there is any truth to this theory. There is official documentation describing several operating modes of the N52 DME including a high output mode which triggers the map thermostat to open up under command earlier than the traditional function of the thermostat. I was always assuming I somehow kept triggering this mode in normal driving. So far, I have been unable to reproduce the fluctuating coolant temps despite colder weather requiring the heater to be on max. I did replace the clutch and flywheel so I haven't done any redline blasts yet, but i have accelerated hard up to 5000rpm several times without issue. Hope this helps

[propaintballa]

So I've just been out to replace the VVT motor gasket and I don't really have anything to report back, other than that the gasket needed to be done and that the test drive seemed smoother, but it was only a short blast. Idle seemed slightly smoother but tbh, I'd call the difference insignificant, if there even is one. So I guess this Rules out the cause of my issue being a vacuum leak. I've reset adaptions again to test tomorrow so I'll keep y'all updated.

The only other thing I have noticed which I am glad I got the chance to record, was a sound that I could describe as a marble bouncing off a granite worktop or something similarly hard, at a random and erratic rate. This rattle is different to the one I posted on here before which sounded more clunky, this sounds more 'tappy'. I videoed from the bottom of the car to rule out the noise being from the gearbox and then videoed from the top. I am convinced my problem is a collapsed valve spring or a lifter/intermediate lever issue. The sound is easily distinguished in the video when I capture it from underneath as the injectors aren't interfering. It sounds like it is coming from the top/rear of the engine. I have also heard a similar sound from the car if I am in a higher gear at lower RPM and I floor the throttle, it gives a similar if not the same sound rattle for a second.

I've also noticed from the video a pretty audible hissing noise when the camera is under the car. I wonder if there is an exhaust leak somewhere... Hmmmm.

https://youtu.be/hopDFho0jFY