[major330i]

I am going to let my intake valves walnut blasted.. I read several posts about walnut blasting and the symptoms which the cars had before the blasting. It‘s seams to be potential solution for this problem especially because there are no fault Codes. I will report in a few weeks after the blasting.

[DaanBMW]

Good luck ! No need on mine since it's port injection. But let us know either way.

[Taskmaster]

Originally Posted by DaanBMW

Good luck ! No need on mine since it's port injection. But let us know either way.

Have you checked your injectors?

[Taskmaster]

Originally Posted by DaanBMW

Still not solved it. However during the colder season it's a bit better and it gets less noticeable.

List of parts swapped out: spark plugs, coils, maf, solenoids, vvt motor, camshaft positioning sensors, vvt check valves, fuel pump ECU.

Also cleaned throttle body.

Also all my software is the latest possible via INPA.

When my car cut off during coasting, it ended up being the fuel pump. It's either the pump or the injectors in my opinion.

[DaanBMW]

Originally Posted by Taskmaster

Have you checked your injectors?

No. Do you mean via software or on a bench ? I figured that any fuel or air issues would manifest at idle and/or other operating regimes than just from or to low rpms.

Originally Posted by Taskmaster

When my car cut off during coasting, it ended up being the fuel pump. It's either the pump or the injectors in my opinion.

That was my next step, given major's post now I'm on the fence...

[Taskmaster]

Originally Posted by DaanBMW

No. Do you mean via software or on a bench ? I figured that any fuel or air issues would manifest at idle and/or other operating regimes than just from or to low rpms.



That was my next step, given major's post now I'm on the fence...

Either/or. Just because they don't trip a code doesn't mean there isn't a problem. My fuel pump didn't trip a code at first either. Have you checked the fuel filter as well?

You can buy the who remanufactured set of injectors for about 300(after core) from ECS. The fuel pump was about 250ish (or less) when I bought mine a few years back. Both should be pretty easy to change.

[DaanBMW]

Originally Posted by Taskmaster

Either/or. Just because they don't trip a code doesn't mean there isn't a problem. My fuel pump didn't trip a code at first either. Have you checked the fuel filter as well?

You can buy the who remanufactured set of injectors for about 300(after core) from ECS. The fuel pump was about 250ish (or less) when I bought mine a few years back. Both should be pretty easy to change.

Yeah the fuel pump I can see as a possible culprit, the injectors not so much. Fuel filter is in the tank, not looked at it but I use plenty of additives (liqui moly). + Not sure what is there to check, I don't expect clogging with debris that can be seen with the naked eye. I also don't see the failure mechanism of the filter to/from idle only.

Chasing this with part after part for no good result is not something I look forward to anymore. Got tired after so many trials. Need a success story or a failure mechanism that makes sense.

Leaning towards software interactions that just can't handle anything than a perfect (read new) car, kinda like a tolerance stackup that builds over time and the system can't deal with. The car clearly finds the necessary power (fuel/air mix) on either part of the transition to/from idle. Yet for a brief moment it doesn't. What can cause this ? It's almost like the ECU is asleep - only for a brief fraction of a second and only from idle or from coasting to idle (AFAIK coasting in gear shuts the injection off entirely) - and wakes up late, then makes up for it. It is that initial spritz either from no fuel to idle, or from idle to going faster, that is not found in due time.

[Elias_E90]

Could clogged cats cause this ? O2 sensors? I think u checked eveything else.. try to drive it with the maf disconnected, maybe it goes into open loop mode (like alpha n) it ll help to know if it hardware or sensor

[DaanBMW]

Originally Posted by Eliase90

Could clogged cats cause this ? O2 sensors? I think u checked eveything else.. try to drive it with the maf disconnected, maybe it goes into open loop mode (like alpha n) it ll help to know if it hardware or sensor

Interesting, this is new to me...

I recall disconnecting the maf when I was suspecting it, before I went ahead and replaced it. Don't recall for sure but I believe it went into a fairly powerless limp mode ... could be wrong as I might confuse it with the TDI that for sure does that.

But - can you confirm what this is going to tell me: From reading up a bit I understand the "open loop" you refer to is for the o2 sensors. So you think the lack of maf info will trigger the dme to open the o2 loop even when engine is at temperature, and if it does and I don't experience the rpm drop/hesitation then the o2 sensors are f'ed. Is that what you have in mind ? If so, how do I know which loop I'm in ?

[Elias_E90]

I cannot confirm, i lack experimenting with these cars.
What i do know is disconnecting the maf will make the dme use old stored data. Disconnecting the o2 sensors will put it in open loop, however you said the problem occured when transitioning to full throttle. i still suspect your catalytic converters. Also the o2 sensor usually throw codes

[DaanBMW]

Originally Posted by Eliase90

I cannot confirm, i lack experimenting with these cars.
What i do know is disconnecting the maf will make the dme use old stored data. Disconnecting the o2 sensors will put it in open loop, however you said the problem occured when transitioning to full throttle. i still suspect your catalytic converters. Also the o2 sensor usually throw codes

Yeah, it occurs when transitioning to more throttle not necessary full throttle, and also taking it out of gear after coasting (on flat or downhill). So the best way to describe is as to and from idle.

On "from idle" you basically step on the gas to drive off, and the rpm gauge goes up, then levels or drops off a bit, then finally goes back up again - this is the hesitation. I think this is still within the closed loop but I'm not sure.

On "to idle" once are coasting in gear due to say a traffic light or upcoming turn, and before (or while) you apply brakes you take it out of gear. rpms drop from wherever you were coasting at (> 600 idle speed) to under idle speed, and if a/c is on they drop so hard the engine at times can stall. This rpm drop does not happen predictably all the time, and most times it does the engine recovers back to idle, but not always. I think this should for sure be within the closed loop but again I'm pretty new to this concept.

[Elias_E90]

Hey man, if i were you, i would do the below : (all is preventive maintenance and stuff that should be done at least once when u own the car)
Clean injectors
Check/replace coil pack and spark plugs
Clean maf
Clean vanos solenoids (or replace depending on debris)
Clean vanos return filters
Use redline fuel system cleaner
If u have done all this and u still have issues, check if your cats are clogged (it is easy, just remove the o2 sensor for the exhaust manifold near the firewall, then with a light look straight through)

[Elias_E90]

A bad o2 sensor will give you a ses light.. also a vaccum test is good. An easy way to do a vaccum test is : get a bottle of carb cleaner, let the car start and warm a bit then spray everything near the intake (arround maf and throttle body, arround disa, near fuel rail and near the cylinder head where the intake manifold botls in

If a leak is present the idle will change and fluctuate when spraying.
If the issue persists remove the bms powerbox, reset adaptations and try the car

Ps : to remove the o2 sensor for checking cats, the easiest way would be using an oxygen sensor socket (basically a long socket with a lobe form cut into for the wire). The wire will twist a bit, so to reinstall count the turns and counter twist the wire so when u install it becomes straight

[stevesingo]

I had an issue where upon accelerating from say 20%-60% throttle at 1600-200rpm, the engine would die and then recover.

I did the usual of plug and I cleaned the VANOS solenoids, which were really clean anyway. No change.

Using INPA I carried out the VVT test which compares target cam angle to actual. You basically select the cam angel and look at the response time.

Both cams were sluggish to respond.

I took the plunge and replaced the VANO Solenoids with new from BMW. The response of the VANOS was significantly better, almost instant.

Driving the car, this issue was cured.

[major330i]

Hey stevesingo,
sounds like you had the same issue.. you have also the n53 motor?
i already replaced both vanos solenoids. i didn't get the point about what you did with inpa. What kind of test is "VVT test".. what do you mean by vvt?

I disconnected the maf and like eliase90 mentioned, the hesitation without maf is gone. It still vibrates a little in idle but the hesitation at lower rpm isn't present. I know the car runs in "emergency mode" without maf. But i don't know how this emergency mode actually function. I think without maf the egr doesn't work and the car runs in homogen mode. This means that the car has this hesation because of the stratified mode (just my thoughts).

This hesitation at low rpm feels like the car didn't get enough air when i suddenly accelerate.. that would be logical because every time when this hesitation happens the rpm drops for this moment -> cause the car gets the fuel but not enough air?

i plan to do the walnut blasting..

[stevesingo]

I don't have access to INPA anymore and the INPA I had was all German.

There is a VVT (Variable Valve Timing) test function hidden somewhere. You can basically, set the idle speed to a predetermined value (1200) then chose an number of cam position targets which swing through the full range. The INPA display gives an indication of target vs actual. When making large changes to the target, it was plain to see that the response was sluggish.

Mine is N52, but the VVT principal is the same.

[major330i]

Okay i will check this. thank you.

Hey guys to get this problem solved i started to check step by step all parts that can cause those hesitation and a rough idle. So i reinstalled both DISA Valves. They came out closed and it was not possible to move these valves (i think this is how it should be). BUT! the green sealings around the framework are not complete. There are little pieces missing. I am not talking about the o ring sealing i mean the sealing on the framework which is in the manifold.
Can those cause an air leak or a malfunctioning disa??

[DaanBMW]

I disconnected the MAF to see if this reveals anything. The car behaves differently and while I'm tempted to say better, I think the response *from* idle is better (less hesitation) but I *think* i still saw an rpm drop from coasting to idle. I need a hot day to assess this better.

I'm still unclear what this would mean though - clearly that the air-fuel mix is off, but due do ... o2 sensors ? the maf was replaced to new by OEM supplier (Siemens), vanos, etc (growing tired of laundry listing it)

I need someone with a better understanding of this n52 closed loop to chime in so I can identify root cause... anyone ?

[PhaseP]

Originally Posted by DaanBMW

I disconnected the MAF to see if this reveals anything. The car behaves differently and while I'm tempted to say better, I think the response *from* idle is better (less hesitation) but I *think* i still saw an rpm drop from coasting to idle. I need a hot day to assess this better.

The MAF also houses intake air temperature sensor, so you disconnected that too. It will be running without knowing correct intake air temperature.

I'm still unclear what this would mean though - clearly that the air-fuel mix is off, but due do ... o2 sensors ? the maf was replaced to new by OEM supplier (Siemens), vanos, etc (growing tired of laundry listing it)

Do you by any chance reseat the MAF connector good, get driving free of this symptom for a few days and then comes back again? This has been an issue in my 2006 N52 and several others 2006 N52 in this board. 2006 N52 has analog MAF sensor though.

The closed loop is a feedback controlled system. Computer continuously measures the amount of oxygen gets into the engine from MAF sensor reading plus intake air temperature sensor. Then tells the injectors to inject appropriate amount of fuel that will burn with the amount of oxygen entering the engine. The 02 sensors on the exhaust measure the amount of oxygen coming out of the engine that has not combined with the fuel by burning it. This is the feedback loop control, computer from this deduces how much it needs to adjust (correct) the fuel amount so complete good burn is achieved. If the correction amount goes over plus or minus 20% (or 25 ? don't remember exactly) then it throws a mixture ratio code, either too rich (too much fuel for amount of air entering) or too lean (too little fuel for amount of air entering). This will be a check engine light since emissions issue.
If computer is able to correct within the threshold it won't throw a code, but still not a very happy engine, something is wrong in one of those sensors or there is an air leak.

If air enters the engine intake after the MAF, this causes lean condition, because more air than computer is told by the MAF is entering the engine.

If the injector(s) are faulty and leak, it will be rich condition, too much fuel.

If 02 sensors are faulty, not sure how they fail, I haven't had to deal with their failure. But there are two sets of 02 sensors, one before catalytic converter, one after for each of the two catalytic converters. I have been told/read that these before after sets can tell the computer if one O2 fails or not. The extra ones after the cats are to verify the cats are working good, but can tell the pre cat 02 sensors are failing also.

Usually you would get an 02 sensor code when they fail.

You have then the "throttle", which on N52 is valvetronic that adjust how much the valves open instead of a throttle butterfly on the intake pipe somewhere. Something wrong here with the sensors can also cause confusion on the computer, because it is also about how much air goes into the engine. There is eccentric shaft sensor for that.

Then there is also the vanos, that adjust how early or late the valves open and close, this can also cause issue. But Vanos looks like also causes its own code to be thrown.

I wrote my own understanding of these, I am not a mechanic nor have education on these.

From what you are describing, there is something wrong directly on the computer's ability to calculate and tell how much fuel should be injected for the air.

If you are not getting any codes, I suggest get INPA and look at the screens that show fuel trim ratios, intake temperature, etc. It may give some ideas, or it may not.

[DaanBMW]

Originally Posted by PhaseP

The MAF also houses intake air temperature sensor, so you disconnected that too. It will be running without knowing correct intake air temperature.
[snip]
The closed loop is a feedback controlled system. Computer continuously measures the amount of oxygen gets into the engine from MAF sensor reading plus intake air temperature sensor. Then tells the injectors to inject appropriate amount of fuel that will burn with the amount of oxygen entering the engine. The 02 sensors on the exhaust measure the amount of oxygen coming out of the engine that has not combined with the fuel by burning it. This is the feedback loop control, computer from this deduces how much it needs to adjust (correct) the fuel amount so complete good burn is achieved. If the correction amount goes over plus or minus 20% (or 25 ? don't remember exactly) then it throws a mixture ratio code, either too rich (too much fuel for amount of air entering) or too lean (too little fuel for amount of air entering). This will be a check engine light since emissions issue.
If computer is able to correct within the threshold it won't throw a code, but still not a very happy engine, something is wrong in one of those sensors or there is an air leak.

If air enters the engine intake after the MAF, this causes lean condition, because more air than computer is told by the MAF is entering the engine.

If the injector(s) are faulty and leak, it will be rich condition, too much fuel.

If 02 sensors are faulty, not sure how they fail, I haven't had to deal with their failure. But there are two sets of 02 sensors, one before catalytic converter, one after for each of the two catalytic converters. I have been told/read that these before after sets can tell the computer if one O2 fails or not. The extra ones after the cats are to verify the cats are working good, but can tell the pre cat 02 sensors are failing also.

Usually you would get an 02 sensor code when they fail.

You have then the "throttle", which on N52 is valvetronic that adjust how much the valves open instead of a throttle butterfly on the intake pipe somewhere. Something wrong here with the sensors can also cause confusion on the computer, because it is also about how much air goes into the engine. There is eccentric shaft sensor for that.

Then there is also the vanos, that adjust how early or late the valves open and close, this can also cause issue. But Vanos looks like also causes its own code to be thrown.

I wrote my own understanding of these, I am not a mechanic nor have education on these.

Yes, I'm with you here all the way, that is my understanding of the closed loop as well, mostly based on previous knowledge of engines.

My questions: when exactly does the closed loop start and when does it end ? Is there anything that changes to or from engine idle, which is where I'm having all the issues ? Is it a transition from closed to open loop ? Is it something else ? What would the availability or lack thereof of the MAF info (air mass, calc'ed via actual flow & temp reading = volumetric flow x density = mass flow) change, if anything, in the engine management scenario? Ultimately the o2 sensors should "see" any rich/lean picture and adjust accordingly even w/o the MAF info (=which should be more of a front end and not influence the back end). More so, any "doubts"/miscalcs reg the air/fuel mixture (or conversely, unmetered air entering the intake) would invariably spill over into other regimes - esp. when the transients are more rapid, like at much higher rpms - whereas mine works really perfectly away from the transition to/from idle (I have no glitches at idle or away from it)

Originally Posted by PhaseP

Do you by any chance reseat the MAF connector good, get driving free of this symptom for a few days and then comes back again? This has been an issue in my 2006 N52 and several others 2006 N52 in this board. 2006 N52 has analog MAF sensor though.
[snip]
From what you are describing, there is something wrong directly on the computer's ability to calculate and tell how much fuel should be injected for the air.

If you are not getting any codes, I suggest get INPA and look at the screens that show fuel trim ratios, intake temperature, etc. It may give some ideas, or it may not.

Issue/Symptom is not intermittent, except that it is much more noticeable when it's hot outside and esp. so if I have the a/c on, and then in extremis is can completely kill the engine. It never happens during colder season, ~fall-spring.

------------------
Breaking NEWS: the rpm drop seems to be occurring with the MAF disconnected as well. The engine behavior/response is for sure different - likely because it uses a "safe" air/fuel mixture (read rich) and thus the car feels more responsive overall - but ultimately the symptoms are still present.

I feel that somehow the mnmgt system gets one piece of info wrong for just a split second ONLY in these from/to idle transitions, and thus gets the whatever-should-happen delayed, for just a fraction of a second - after which it corrects itself - via o2 sensors, or simply rpm readings, or ?? which is why i changed among other things vanos, check valves, vvt motor, maf, camshaft positioning sensors, fuel pump ecu, all for naught.

What in god's green earth is wrong with the car ? I cannot but blame the lousy electronic management of the engine, incl. vvt, adaptations, etc., the whole shebang. I've never seen this happen in simple mechanically-driven systems. Another system well-suited for the bimmer target audience: buyers of new cars / ppl with cash to burn.

Can the vvt system be disabled ? I've subscribed to a thread asking as much, but have not seen any solutions...

[Elias_E90]

Talk to the tuners, to disable the valvetronic, it should be always rotated to full lift, and the throttle body will control the fuel depending on the air entering. Also this thread http://www.1addicts.com/forums/showthread.php?t=1490882 may have your same problem, he disconnected the ess sensor and tried the car

[DaanBMW]

Originally Posted by Eliase90

Talk to the tuners, to disable the valvetronic, it should be always rotated to full lift, and the throttle body will control the fuel depending on the air entering. Also this thread http://www.1addicts.com/forums/showthread.php?t=1490882 may have your same problem, he disconnected the ess sensor and tried the car

Thanks ! seems we have some convergence on the use of ess to disable vvt.

the thread I was referring to: http://www.e90post.com/forums/showthread.php?p=23163377