[ADG91]

Hey all
Ive had a long running niggle with my 125i - in relation to a slight lack of performance and not running as smoothly. Whereas ive not had much to go on, i now recently had some symptoms to go by what’s causing it but now have various ones that may or may not be related so am hoping to get some insight. - Sorry this is a bit long winded.
(Just for the record i have newish plugs/coils, VCG, air filter and with annual oil changes etc)

I currently have the following codes
2A31
Ox2A31 Valvetronic, eccentric shaft sensor: guide

2A33
Ox2A33 Valvetronic, eccentric shaft sensor: guide

2A35
Ox2A35 Valvetronic, eccentric shaft
sensor: guide

29E0
Ox29E0 mixture control

29E1
Ox29E1 mixture control 2

2A37
Ox2A37 Valvetronic, eccentric shaft sensor: plausibility

The car seems a bit lethargic at lower speeds mainly, the fuel consumption is higher and im also occasionally getting a vapour-ey burnt oil/rubber type smell along with a high pitch squeak from the oil filler cap area when applying throttle (again all may or may not be related. However my idle is smooth (has been lumpy before) and oil doesn’t appear to be dropping/burning. The revs sound a bit knocky at times but not all the time.

So i took my car into my indy bmw tech to see what on earth is going on. Unfortunately after doing smoke tests, diagnostics checking DME tolerances etc- apart from the obvious ESS fault, he could not find what was causing the mixture control fault and whether everything was related. Also no signs of any vacuum leaks. He advised it is running just within tolerances before ISTA flags up whats at fault with air/fuel ratio - but acknowledged its not quite driving 100%. Of course the replacing the ESS will help but has advised not to do this until we’re completely certain whats causing the mixture control fault to rear its head.
A bit frustrating but at least he has not advised to throw parts at it. As all this testing is costing money i will stop pulling it apart - at the same time I would like to try try at least narrow down if im looking at something really obvious that everyones overlooked or its just unfortunate that a few things have started failing at the same time - unsurprisingly over winter. The possibility of it being an 02 sensor or injector has been considered.

 

[cjk28]

get yourself a dcan cable, get inpa and ista (dont pay), see if you can get more detailed fault descriptions out of them. try ista test plan on the present faults.

inspected oil filter? might be collapsed, not in the cage properly, o ring missing etc

 

[Autosri]

Could be a failed PCV system pulling too much vacuum in the crank case as that can cause it to pull air round the front and rear crank seals and also causes a high pitch squeal at high vacuum
Not sure how the valvetronic engines handles the pcv system though

 

[ADG91]

Thats what i was hoping my mechanic would unearth as he uses the BMW diagnostic software, I initially thought that however im not getting white smoke, dropping fuel, excessive vacuum at the oil cap. There was also no oil around the ESS gasket either. I have dabbled with getting ista myself but outside of code reading im not sure what im looking for. I have a flow chart diagram of what the BMW diagnostics looks for but only produces a solution to the eccentric shaft fault. If i was to get the software is it the fuel trims i need to have a look at?

 

[nivens]

It might not solve your long term issues but have you checked your oil filter hasn't collapsed? They squeal when the engine is hot\high revs and if it's restricting oil flow it'd possibly be the cause of the valvetronic codes you're getting.

 

[Nyxeris]

If you have Bimmerlink/another capable app, you could log the related datapoints across a journey and see if anything stands out. MAF, o2/lambda, fuel trims, etc. with throttle percentage and revs. Make sure the car is good and cold, start your log, then start the engine and idle for a minute or two until you hear the exhaust quieten down. Then drive around gently until it reaches operating temp, once it's there do a few pulls to redline. You want a nice mixture of idling, normal/gentle throttle, and wide-open throttle to see how the fuel trims go at each point. If all the sensor readings make sense, you can look at the black holes in the data i.e. a leaky injector.

I would suggest resetting adaptations but as you have an active ESS issue that might not be a good idea. Not qualified to say.

 

[ADG91]

If you have Bimmerlink/another capable app, you could log the related datapoints across a journey and see if anything stands out. MAF, o2/lambda, fuel trims, etc. with throttle percentage and revs. Make sure the car is good and cold, start your log, then start the engine and idle for a minute or two until you hear the exhaust quieten down. Then drive around gently until it reaches operating temp, once it's there do a few pulls to redline. You want a nice mixture of idling, normal/gentle throttle, and wide-open throttle to see how the fuel trims go at each point. If all the sensor readings make sense, you can look at the black holes in the data i.e. a leaky injector.

I would suggest resetting adaptations but as you have an active ESS issue that might not be a good idea. Not qualified to say.

Thats fortunate as i do have Bimmerlink. I wasnt aware you could use it for logs. Ill give it a try but im not sure what sensor values i need to log. Theres an overwhelming list of things it can monitor but none that say “long/short term fuel trims, 02 sensor” etc

Ill admit im a complete novice when it comes to logging data. Ive only used this app to look for trouble codes.

 

[ADG91]

It might not solve your long term issues but have you checked your oil filter hasn't collapsed? They squeal when the engine is hot\high revs and if it's restricting oil flow it'd possibly be the cause of the valvetronic codes you're getting.

As to this, no I haven’t. Annoyingly i havent got the correct tools to take the filter off. Would this likely cause the burnt oil smell. The thought of restricted oil flow is troubling- are there any other tell-tale signs?

 

[nivens]

As to this, no I haven’t. Annoyingly i havent got the correct tools to take the filter off. Would this likely cause the burnt oil smell. The thought of restricted oil flow is troubling- are there any other tell-tale signs?

I only suffered it briefly, I'd taken it for a service and within the first 1-200 miles I noticed the oil level reading wouldn't settle and I could hear squealing from the filter area once the engine was hot or if the revs were taken beyond 3000rpm. It's a guess but I assume the squealing is due to the oil flow being restricted so could potentially start throwing errors in oil pressure sensitive components if it's bad enough and might be a cheaper fix than the potential that this is related to a worsening of your longer term problems.

 

[ADG91]

I only suffered it briefly, I'd taken it for a service and within the first 1-200 miles I noticed the oil level reading wouldn't settle and I could hear squealing from the filter area once the engine was hot or if the revs were taken beyond 3000rpm. It's a guess but I assume the squealing is due to the oil flow being restricted so could potentially start throwing errors in oil pressure sensitive components if it's bad enough and might be a cheaper fix than the potential that this is related to a worsening of your longer term problems.

I see! Well no such squealing this end. It seems to be coming from the oil cap area at the top of the engine. My oil level reading seems to be ok and has not dropped or anything untoward. I scanned again for new codes today and still sitting with the ESS and mixture faults. I don't know if it was just me but Ithought I could smell a faint whiff of petrol in the cabin when I stopped. Was only once but if that does become a thing I presume that's leaning towards something injector related.

If anyone could advise what's worth logging through Bimmerlink, im able to do so ill give it a go under the different conditions.

 

[ADG91]

Im half tempted to take the plunge on a DCAN cable and ISTA software to try and find out what's going and log through there however Im not sure if ill manage to unearth anything the mechanic hasn't found to be honest - Not sure if its a potential waste of money but would it be more straightforward for running logs as I have no idea where to start with BimmerLink. I wonder is ISTA sort of guides you through it.

Just want to get to the bottom of it and start enjoying the car as im holding out for something big to go at the moment.

 

[Nyxeris]

Bimmerlink is much easier than INPA/ISTA for logging!

I’d add engine RPM, Road speed and throttle pedal percentage to begin with, then just pick stuff related to fuelling. You can check lambda/o2 sensors per bank, I think you can also check fuel mix on the same basis, as well as injectors and ignition timing at per-cylinder resolution.

You don’t necessarily need to know what the exact values mean - if you log both banks lambda sensors and one is fairly steady and the other is all over the place, that might be enough to narrow down a problem.

 

[cjk28]

Don't pay money for ista.

 

[ADG91]

Ok ive managed to locate an obd app with a good level of detail (car scanner). My Bimmerlink is being finicky at the moment and doesnt always connect.

I have a list of sensors that it monitors on the go which ive screenshot below. I can also run logs on these but only 2 at a time at the moment (you have to upgrade to pro for more!) If i can find the below values on bimmerlink, in particular fuel trims, that would be a bonus but there’s nothing on the list of values to log.

If theres any below values that i should focus on to narrow it down it would be great to know. So far there’s nothing that stands out to me, this was driving first thing in the morning about 10 minutes into driving at pootling pace.

It might be worth noting that the car felt smoother to drive and pullled along better during this cycle, weirdly the car drives better after sitting a day or two - almost as though it’s resetting the map.

All in all im just a bit concerned that driving around with a mixture code will cause damage in the long run even though my mechanic has advised to wait it out.

 

[ADG91]

Ok ive got Bimmerlink back up and running and have been keeping a close eye on different sensors and readings etc. I am not sure if its a by product of the mixture control fault but I’ve noticed the coolant temps and engine temps do not seem to climb above 85c. It will gradually climb towards 90 when at idle but most of the time it sits around 78c or so just pootling around town which seems a bit low to me.
Not sure if this points towards a vacuum leak if there’s too much unmetered air getting through somewhere.
Im not sure what else i can do really without replacing major parts and hoping for the best, or to just wait until the poor running causes internal damage which is what waiting for next…

 

[cjk28]

if temps are dropping while driving around (air into radiator) and go up when idling/revving stationary, and in general not getting up to temp, then thermostat is stuck open. should get fault code for this but mine didn't log one when it was at least partially stuck open

 

[ADG91]

Sounds likely! So i presume this is going to be ontop of whatever is going on as I wouldn’t have thought this would like to a mixture fault. This car is seriously testing me right now, getting a nice list of things piling up!!

 

[nivens]

Someone much smarter (Nyx) will be able to confirm but I'm fairly sure the engine map is tied to temperature on these so it'll be running rich if it's cold to try and heat up to get into it's optimum temperature range. Quite a pricy issue considering it's generally worth throwing in a new pump too if it's not been done but hopefully it solves some of your problems.

The joys of running aging cars!

 

[Nyxeris]

🤓

78c sounds like a thermostat stuck open to me!

Heat management

For the cooling system with electric coolant pump, the possibilities of the conventional cooling system are exploited.

The following components are influenced by the heat management:

• Electric coolant pump
• Characteristic map thermostat
• Digital engine electronics

The cooling power of the system is adapted by means of a freely variable volumetric flow of the coolant.

The heat management determines the current cooling requirement and regulates the cooling system accordingly. Under certain circumstances, the coolant pump can even be switched off completely, for example to accelerate heating of the coolant in the warm-up phase.

If the engine is not running but very hot, the coolant pump will also work while the vehicle is out of use. The cooling power can be requested independent of the engine speed.

The heat management now means that, over and above the map thermostat, various characteristic maps can be used for control of the coolant pump. In this way, the engine control unit can adapt the engine temperature to the driving characteristics.

The engine control unit regulates the following temperature ranges:

• 112 C = Economy
• 105 C = Normal
• 95 C = High
• 80 C = High and regulation by the map thermostat

If the engine control unit detects the economical operating range "Economy" due to the driving characteristics, the DME regulates to a higher temperature (112 °C). In this temperature range, the engine is operated with a relatively fuel requirement. The friction inside the engine is reduced at higher temperature. The temperature increase thus favour the lower fuel consumption in the low load range.

In the mode "High and control by the map thermostat", the driver wants to use the optimised power output development of the engine. To achieve this, the temperature in the cylinder head is lowered to 80 C. This reduction leads to better cylinder filling, which increases the torque of the engine. The engine control unit can now regulate to a certain operating range adapted to each driving situation. This means is it possible to influence consumption and power output by means of the cooling system.

 

[ADG91]

Someone much smarter (Nyx) will be able to confirm but I'm fairly sure the engine map is tied to temperature on these so it'll be running rich if it's cold to try and heat up to get into it's optimum temperature range. Quite a pricy issue considering it's generally worth throwing in a new pump too if it's not been done but hopefully it solves some of your problems.

The joys of running aging cars!

Pretty frustrating, so potentially a stuck open thermostat could be causing this or the eccentric shaft or both at the same time.There doesnt seem to be anyway to be sure.
I will say though that before these faults arrived it did seem to get up to temp absolutely fine.
Im half considering chopping the car in at the moment as its like hitting your head against a brick wall and all bmw specialist ive visited cant find a clear cause. So am entertaining the thought of cutting my losses before it all goes wrong. I have no idea what id replace it with though.