[HotSpicyChicken90]

Hello lovely people,

I have this problem since two months now, which literally drives me crazy!
About the symptoms:
Very noticeable jerking, stuttering and starting difficulties when the engine is warm/hot. Sometimes the engine won't even start at all. Engine has starting-problems.
The problem only occurs after the engine has warmed up and ONLY when starting/idling.
Error only occurs after about 10-15 minutes after the car has been shut down.

ISTA says P0172: system too rich; which means that the DME either detects too little air or too much gasoline.



So to reproduce the problem:
1. Car start perfectly when cold, not a single problem or vibration!
2. I drive half an hour normally (City/motorway)
3. Shutting the car off.
4. Waiting 15 - 20 minutes
5. Restarting the engine
6. Either the car starts with huge difficulties (sputters, shakes, jerks) OR it stalls and shuts off immediately.




So far I've replaced:
Intake manifold gaskets. (Even though this can't be the cause of the issue, since in the event of an air leak the DME would detect too much air and not too little (or am I wrong there?)
6x injectors
6x spark plugs
6x ignition coils
MAF
2 O2-sensors
2 MAP sensors
Air Filter
Engine oil change (with filter)
2 Camshaft Positioning sensors
Cleaned both Vanos-Selenoid
Crankshaft Positioning sensor

I'm desperate and on the verge of a mental breakdown

Someone got an idea?

Any help is appreciated

[M_Bimmer]

I don't see the coolant temp sensor on parts replaced....since most other items that cause this problem is on your list of items have already been replaced.

It looks like you've thrown a lot a parts at this issue. If you are running ISTA-D, you should use the troubleshooting plan and the real-time data measuring data available within ISTA-D.

Typically the coolant temp sensor doesn't throw a code, but should log entries in your ECU...13621433076 and/or 13627580635...I had to guess on mfg date and picked 5/2012 N55.

Cheers

[BurrNinja]

Id assume with new injectors they were coded? Just an idea.

[HotSpicyChicken90]

The Problem was there before changing the injectors.
Can extremely short-distance-driving be the cause of this issue?
Im not a trained technician, but a regular guy who’s passionate about cars.
Ok so, i tried to use live data, but i am overwhelmed. What data should i look at?
everything seems fine to my untrained eyes.

ISTA wants me to check the intake manifold, although this can’t be the issue since an air leak would cause a lean condition; right????? or am i missing something important?
And why does this happen only when the engine is warm??
i’m pulling my hair out

thanks

[beastlysun]

I had same issues. Not on 535i (so it can be something else) but on 523i N53B30 but result was that after one of my injectors went boom (it literally split) my HPFP followed it. Check you low and high fuel pressure

[HotSpicyChicken90]

I'm struggling to understand why an intake leak would cause a rich mixture?!ISTA says I have to check the Intake system...
(I already checked 3 times!, although without a smoke-tester)

Wouldn't an air leak cause a lean condition since unmeasured air enters the engine?

OR

The ECU demands more fuel because there's an intake leak. In other words; since there is unexpectedly more air in the system, the DME has to spray more fuel to compensate the unmeasured air; hence "system too rich"? Therefore the ECU recognised that more fuel is sprayed into the engine as usual and because of this the DME says: system too rich?

-----------------------------------

Intake leak = More (unmeasured) air requires more fuel to be sprayed into the engine to compensate the "unknown" air, therefore "system too rich" --> Because the DME has to put more fuel then normal?

OR

Intake leak = More (unmeasured) air requires more fuel to be sprayed into the engine to compensate the "unknown" air, therefore "system too lean"? --> Because there is more air then normal?




Am I losing the plot here? Both make sense, but which one is scientifically and physically right?

[beastlysun]

Any errors regarding NOX sensor? Check values if able to

[HotSpicyChicken90]

No codes

I will check later

[beastlysun]

And check that dreded fuel pressure as well. I don`t know what pressure should be in 535i but it should be stable (mine was on 200 bar) with higher pressure on kickdown.
In my instance when temperature got higher, pressure was droping quite hard until it droped bellow 130 on load and shut down HPFP. Than it was struggling to come home at 6 bar of pressure from LPFP, until it sat down for a bit, or errors reset

Got also same misguiding errors

[HotSpicyChicken90]

Would't a faulty HPFP cause an Error in ISTA?

[beastlysun]

nope ... mine showed everything from temperature of transmision to coils. Not even dedicated HPFP test found the issue since it test only if that pump can pressurise to 200bar and stay that way for set amount of time. It does not test high load and troughput

[HotSpicyChicken90]

So i suspect Nr. 3. Reason being it released some pressurised air as i moved it.
I will test it later

http://bmwfans.info/parts-catalog/F1..._turbo_charger

[mashpotato]

You don't have any other codes besides fuel rich in ISTA-D?

Do you have any vacuum leaks(ex. Valve cover)? Are you holding boost (no leaks around charge pipe connections)?

There was someone here who had a bad new injector and screwed up the spark plug too. Would STFT show anything? (Dumping fuel when the car is warm, when cold everything evaporated?)

Didn't mix up the primary and secondary 02 sensor right?

Just throwing it out there

[HotSpicyChicken90]

I observed that the valve cover does leak AGAIN (after i changed it perfectly)!
i think because the inner pressure of the valve cover has somehow increased. Can this be caused by extreme Short-distance-driving and several on/ff cycles?

[mashpotato]

No. As long as you warm up your car before driving hard, often oil changes. Half an hr drive daily (10-15min warmup) is fine. I do the same thing.

Make sure your VC is good, and all those hose connections. I'm not sure if this is your only issue.

[HotSpicyChicken90]

ok i will do an extensive diagnose later i keep u posted!

[ezaircon4jc]

Originally Posted by HotSpicyChicken90

...
Intake leak = More (unmeasured) air requires more fuel to be sprayed into the engine to compensate the "unknown" air, therefore "system too lean"? --> Because there is more air then normal?...?

Unmetered (unmeasured) air is just that. It will probably never be noticed at "higher" rpm. It should cause idle inconsistency, like roughness or surging.

[ezaircon4jc]

Originally Posted by HotSpicyChicken90

I observed that the valve cover does leak AGAIN (after i changed it perfectly)!
i think because the inner pressure of the valve cover has somehow increased. Can this be caused by extreme Short-distance-driving and several on/ff cycles?

Did you torque the bolts correctly in the correct pattern? Like head bolts, the intake bolts must be torqued in a specific order to prevent warping.

My wife does nothing but short trips and doesn't have any problems; outside that I need to put the battery maintainer on once a month or so. Short, putzing around town will not cause intake leaks. Why would the inner pressure of the intake increase? An engine is nothing more than an air pump. There is (or should be) vacuum in the intake, not pressure. Pressure in the intake would be very, very bad.

[HotSpicyChicken90]

Im still confused; why would an intake leak cause a rich mixture

[ezaircon4jc]

Originally Posted by HotSpicyChicken90

Im still confused; why would an intake leak cause a rich mixture

It won't. It will be lean; how much depends on the amount of unmetered air.

[HotSpicyChicken90]

So guys; I think I'm getting closer to the root cause.

I disconnected the throttle-body, and..... no hesitation! Furthermore the TB makes strange knocking noises after the car has been shut down. So I bit the bullet and ordered a new TB. This time I am confident

Quote from ISTA:
Idle speed control

For idle speed control, the Digital Engine Electronics (DME) control the following factors:

Air mass (via Valvetronic and electrical throttle-valve actuator)
Injected fuel quantity
Point of ignition.
The set engine speed when idling depends on different conditions, for example coolant temperature or power requirement of the auxiliary components.



source: https://www.newtis.info/tisv2/a/en/f...speed/F7fwX8Ln

[HotSpicyChicken90]

Originally Posted by ezaircon4jc

Did you torque the bolts correctly in the correct pattern? Like head bolts, the intake bolts must be torqued in a specific order to prevent warping.

My wife does nothing but short trips and doesn't have any problems; outside that I need to put the battery maintainer on once a month or so. Short, putzing around town will not cause intake leaks. Why would the inner pressure of the intake increase? An engine is nothing more than an air pump. There is (or should be) vacuum in the intake, not pressure. Pressure in the intake would be very, very bad.

Yes I did