N52 hesitation, stuttering, jerking, surging etc

[ph001]

[propaintballa]

So, I'm pretty livid. Changed the motor relatively quickly as I've done it once already, turned the car on to "position 2" so the motor cycled, did this a couple of times then started the car. Rough Idle still present. Let it settle a bit then turned the car off and did the end stop learn cycle in ISTA. It learns the end stops fine but throws a code, which is normal as it comes up in a dialogue box during the learn process. Start the car and I can tell it's not using valvetronic because of the slow revving and you can hear the classic 'sucking' noise of a throttle body. Look for codes again, nothing. Keep trying to cycle the ignition to get it to reset and it's having none of it. Looking at INPA, confirmed there was no movement of the VVT motor. Drove it then it threw a 2A43 code - Valvetronic thermal overload protection. I clear this and eventually get it to run with valvetronic and not the throttle body. Car seems okay but I also reset adaptions so that is likely masking the problem still. To top it all off, once I got it running using valvetronic and took it for a drive, I got back home and let it idle and it's pulsing up and down by like 50-100 rpm, constantly. Also, when turning the car off, the VVT motor made an unwinding sound several times, kind of like one of thos toy cars you pull back and let go. So that's great.

So as it stands, the car is more broken than it was and I have no idea why. Without putting the old VVT motor back in I won't know if it's the "new" motor causing all those faults or now something else. I suspect the motor. The old motor didn't throw any codes after learning end stops. I'm going to drive it today and see what happens. As it stands though, I'm raging. I had a number of reservations about the motor fixing the problem, but I certainly didn't expect it to get worse.

To throw something else in the works, my car has had a replacement battery at some point, and judging the fact that the previous owner didn't even know the car had a two part tailgate, I suspected it hadn't been registered properly, but instead, just thrown in like you would on a 'normal' car. ISTA confirmed this with no history of a battery change. I am yet to check what Ah the battery currently is but it's registered as 70 currently. I am probably clutching at straws here, but I know these cars can suffer really badly from electrical/battery related problems. I wonder if it's possible that this is causing problems with the battery not being charged enough or too much etc. Does anyone know if there is a way to register the battery historically, as I wouldn't want to register the battery as new now as I have no idea how old it is.

[ph001]

No battery registration on E85 / E86 N52 but not sure about the 325i. They are sensitive to poor condition batteries though - this was mentioned very early on (2nd post on thread actually).

Bummer about the valvetronic motor - I really had my fingers crossed for that. You were always going to have to eliminate it from the equation based on the symptoms. I don't quite get how it could be worse / different though. That doesn't make much sense. Was it a new motor or a 2nd hand one? Do you think it just needs to adapt to the the motor for a few drive cycles perhaps.

There's only VANOS left on my list now

1) Observe O2 sensor voltages in INPA
2) Fit new battery
3) Replace coil packs and plugs
4) Replace EGR valve and check pipes to sump for blockages
5) Replace / inspect second DISA valve ???
6) Replace valvetronic motor
7) Have VANOS unit stripped and inspected.


Symptoms
Hesitation/jerking when accelerating from low RPM, most prevalent when in a high gear
Juddering/surging when going constant speed or applying light throttle, particularly around 1500-2000 rpm
Strange behaviour when decelerating in gear, similar to jerking when accelerating but more random and like someone is poking the throttle as the car slows
Various noises, high pitch marble-like rattle towards the rear of engine
Rough/shivering idle
Blowing-like sound from exhaust on hard acceleration, very subtle but either sounds like a leak or gasses not escaping properly


Parts replaced

DME update to latest versions
Both VANOS solenoids
Valve Cover gasket
Eccentric shaft sensor and seal
MAF sensor
VVT Motor Gasket (found vacuum leak around it)
Intake manifold gaskets
6 Bosch Coils
6 NGK Spark Plugs
CCV and 3 main CCV hoses
5w30 LL04 Oil and filter
Inner DISA valve
Cleaned VANOS check/non-return valves

[propaintballa]

No battery registration on E85 / E86 but not sure about the 325i. They are sensitive to poor condition batteries though - this was mentioned very early on (2nd post on thread actually).

Bummer about the valvetronic motor - I really had my fingers crossed for that. You were always going to have to eliminate it from the equation based on the symptoms. I don't quite get how it could be worse / different though. That doesn't make much sense. Was it a new motor or a 2nd hand one? Do you think it just needs to adapt to the the motor for a few drive cycles perhaps.

There's only VANOS left on my list now

1) Observe O2 sensor voltages in INPA
2) Fit new battery
3) Replace coil packs and plugs
4) Replace EGR valve and check pipes to sump for blockages
5) Replace / inspect second DISA valve ???
6) Replace valvetronic motor
7) Have VANOS unit stripped and inspected.

Yeah, the E90 has the Intelligent Battery Sensor with the whole battery registration process. Yeah totally, I did test the battery though for holding voltage and the draw during start up to make sure it didn't go too low, which it didn't, so ruled it out. Seems to crank normally to me, it's just whether the charging system could be doing weird stuff with other things if it's trying to push more charge to what it thinks is the original battery, or not enough etc. Unlikely, but I guess at this stage, anything is possible.

The VVT motor is used but "tested". I always knew that was a risk to be fair, but it beat £150 quid for a brand new one, or so I thought at least. I think I will leave it in for a few more drive cycles, as you say, and see what happens. If it stays the same or I get codes again I'll put the old one back in and see what happens at that point.

[ph001]

I feel your frustration but it won’t be the lack of battery registration causing your issues, you can be sure of that.

Perhaps you could contact Dr. Vanos from the web and ask him if the fault symptoms fit with vanos issues?

[propaintballa]

I feel your frustration but it won’t be the lack of battery registration causing your issues, you can be sure of that.

Perhaps you could contact Dr. Vanos from the web and ask him if the fault symptoms fit with vanos issues?

Almost certainly not. So after my post I started the car and got the same fault code which made the car disable valvetronic again. Since then I have not had the same problem, however, the idle seems different to me as do the driving characteristics, which makes me think the problem could still be the valvetronic motor. However, without spending 100+ on a new one, I won't know for sure. The idle when I start the car is smoother with less fluctuation, but still rough and still fluctuates. When the car is up to temp and idling, the RPM seems to pulse up and down by about 50 RPM. When driving, I am pretty sure the hesitation, stuttering and lack of power is worse and at different points in the rev range. I am really not sure what to do. In the interim I think I am going to have to put the old motor back in and see if the faults carry back or whether the change is due to the 'real issue' getting worse. I am losing the will to live with this now.

As for VANOS, I know for a fact these symptoms fit with cam bearing ledge wear which is an issue on these engines, albeit rarely, whatever that really means. I'm sure a vast majority of the CBL wear problems aren't documented, and there are a fair number of them that are. The only reason I don't think it's this is because the car was kept to the BMW service interval and serviced there a majority of its life. The only problem with this is that means it was kept to the long oil change intervals. I did inspect a couple of cam lobes when I took the valvetronic motor back out and they look spotless. In what I have seen, it would not be uncommon to see quite a bit of wear on these if the CBL is worn. This is the problem I have always been praying wasn't causing my issues, whilst simultaneously having a bad feeling is the culprit.

[propaintballa]

Small update:

I reinstalled my original valvetronic motor which didn't throw any codes or anything after it was installed like the replacement one did. However, the issue is still very much present and seemingly getting worse. If I had to correlate this problem with a potential determining factor, I'd say it seems worse since we have been having hotter weather.

I think I am going to revisit the VANOS screen on INPA and see what's going on there as I feel that's the only thing left. I am convinced this is a timing issue related to oil pressure. I think I am going to check the VANOS non-return valves again, as although they were clean before and I cleaned them off, I forgot to check they actually functioned as a one-way valve. I have read several instances of this solving similar issues. So in the interest of finally ruling that out, I'll do that.

I'm not really sure what else to do tbh, short of setting the fking thing alight. On another note, there is a chump on YouTube by the name of "BMW Doctor" who suggests there is a recall out for my vehicle addressing a power supply related issue, though I can't see any evidence of this. If it does materialise, there is a chance this could be a factor.

[ph001]

Could be VANOS, right back on the first page we did note that my Sensor signal vanos adaptations looked quite a bit different to yours. Trouble is we are comparing a 2.5Si to a 3.0Si.

[propaintballa]

So I got the VANOS non-return valves back out and they were just as clean as when I took them out the first time. Cleaned them off and gave them a good suck n blow, and can confirm they function properly, which is a shame. Revisited the VANOS screen on INPA and to be honest, there's nothing that stands out as being abnormal.

I'm getting this hunting idle more and more now and also getting increasingly fed up. Every time I think I've reached peak fed up-ness, I get more fed up.

I have bought new engine mounts as they definitely need doing and I am hoping the problem will become less obvious so I can just forget about it -.-

[propaintballa]

Well then, it's UPDATE time... So whilst ignoring my car's issues in the best way I know how, which is continuing to research the damn problem, I may have had a breakthrough!

Building on what I have thought for a while, that this is a timing related issue, I began looking for things that can affect timing. Now, our engines are obviously a little more complex than the average 4 banger, but hear me out. I was watching my fuel trims and timing graphs on my phone, which isn't super high fidelity, nor is it easy to do whilst driving, but I was seeing trims which I think are abnormal during different driving conditions. Flooring the throttle I was seeing negative spikes in short term trims and some weird timing type behaviour.

For a while I've had this strange problem where I press the throttle and hold it in a constant position (confirmed by OBD readout), the revs will rise and then start to fall. This made me think it could be a fueling issue again. Over the last few weeks, I've been noticing a hunting idle more and more, whereby the revs would settle to the normal mark and would pulse up and down by about 50-100 rpm. If I rev the car the revs will rise then drop, sometimes falling below the normal idle speed then coming back up.

So I'm thinking, what can affect fuel trims, hunting idle, timing and is something that is plausible... Here I am, back looking at the pre-cat oxygen sensors. My sensors are original, which means they are 14 years and 100k miles old. Being the 5 wire, wideband type, I can't see anything other than voltage in INPA, which as we know, looks normal. But the more I looked into this, the more I read how much failing ones can affect timing, hunting idle and the correct fueling, as you'd expect. I had doubts because the idle issues are pretty evident from cold start, but monitoring this shows that my car, with the current weather, enters closed loop after about 20 seconds. So I thought, why not just unplug the bast**ds so the car runs in open loop all the time.

What can I say, the car runs infinitely better. There is still the odd hicup randomly when I floor the accelerator at low revs, but I'm not sure if this is a byproduct of shot engine mounts (which are being changed next week), or it running in open loop. I suppose you could expect less than best running in open loop. But, the hesitation and surging around 1500-2000 rpm feels like it has improved by about 90-95%, to the point where if I ever feel anything, I really have to be waiting for it. For a car to run this well in open loop with no oxygen sensors tells me I need two new pre-cat sensors.

What are people's thoughts on this? Has anyone experienced something similar?

[Capa]

Honestly i've not heard of anything of the sort beforehand. But I'm bloody glad that you've at least managed to highlight the area of the problem.

If I were you, I'd don a questionable accent, have a few pies and start a youtube channel about your fix....

... Seriously though, good work. I presume the plan is to re-introduce them one by one and see if the issue becomes more evident, then line up a replacement?

Given how rich mine is running, I'm sort of tempted to give this a go as well.

[propaintballa]

Honestly i've not heard of anything of the sort beforehand. But I'm bloody glad that you've at least managed to highlight the area of the problem.

If I were you, I'd don a questionable accent, have a few pies and start a youtube channel about your fix....

... Seriously though, good work. I presume the plan is to re-introduce them one by one and see if the issue becomes more evident, then line up a replacement?

Given how rich mine is running, I'm sort of tempted to give this a go as well.

Hahah, I can only wish to change the youtube game like him though. I was going to do that, I also thought about only buying one to see if it improves the situation, but I figured I could end up in a situation where they are giving more conflicting information to the DME so I've just bitten the bullet (for the millionth time) and got two new Bosch sensors from OPIE as they have 15% off at the moment. I'm not sure when they will arrive but I'd imagine it will be next week some time. This is really it though, if this doesn't solve the issue, I'm done!

[ph001]

Well the o2 sensors were NUMBER 1 on the list, which is why they were given a lot of scrutiny in INPA right back on the first page. I think we concluded that they looked very similar readings to my healthy 3.0Si (both almost bang on 2V) so looked OK. I'm still not convinced of the readings for those in INPA though (for either of our cars) as I was sure they should swing around in terms of voltage. Really need a scope on them to be certain.

Few things that make me a little sceptical of an o2 sensor issue though - the signal is only part of the control loop at idle and steady state throttle. It is completely ignored at wide open throttle. I guess the big question is - does the car behave well at full throttle openings?

[propaintballa]

Well the o2 sensors were NUMBER 1 on the list, which is why they were given a lot of scrutiny in INPA right back on the first page. I think we concluded that they looked very similar readings to my healthy 3.0Si (both almost bang on 2V) so looked OK. I'm still not convinced of the readings for those in INPA though (for either of our cars) as I was sure they should swing around in terms of voltage. Really need a scope on them to be certain.

Few things that make me a little sceptical of an o2 sensor issue though - the signal is only part of the control loop at idle and steady state throttle. It is completely ignored at wide open throttle. I guess the big question is - does the car behave well at full throttle openings?

Yeah so I looked into this quite a lot because I had always thought oxygen sensors give that oscillating read out as you say, but the 5 wire, wideband type that we have, don't. They are supposed to give a constant voltage as we see on ours. That was my takeaway message from my reading anyway. There is actually some really well documented cases of various oxygen sensor faults that cause my symptoms, including ones that appear to be working as they should.

https://www.aa1car.com/library/wraf.htm

I'd certainly say a majority of my problems are occurring at idle and during steady throttle. I wouldn't say it behaves as it should at WOT. Of course, It is possible that my VVT motor is still part of the problem, but I will tackle that when I have installed the new o2 sensors and have hopefully removed the idle and surging/hesitation problems.

[ph001]

Cool. I'm sure you will let us know how you get on. Right back on page 1 you did also say that you had a qualified mechanic check out the o2 sensors who said they were good, but wouldn't be the first time someone got that wrong! Good luck anyway.