[ssgm1x]

I could use some help troubleshooting my F10 N55 PWG via ISTA+. I am trying to narrow down the cause of rough idle/Misfires after an Operating Temperature Re-Start. I get multiple cylinder misfires during restart when cars hot. . I have ISTA+ pre installed on my PC if anyone can direct me in the right path to narrow this down. Other than Rough running cylinder test or misfire counter what else can i do? Can i troubleshoot injectors?

[5soko]

You can run a vanos test and valvetronic tests to mark those off the list.

Not sure if i ever saw injector tests, will have to check in ISTA.


How many miles on the car?
How old are the plugs?

Also, which cylinder are misfiring?

[ssgm1x]

Originally Posted by 5soko

You can run a vanos test and valvetronic tests to mark those off the list.

Not sure if i ever saw injector tests, will have to check in ISTA.

I did a vanos limits test. Where it relearned the limits. It actually cycled 450 times. Then cycled another 30 times. I'm having a rough idle. Misfires at start up and car runs rich. I checked O2 sensor values. Pre cat cycled between .1 and .9 at idle which is good. Post Cat stays at about 1.4 at idle and does not move. Pretty sure that's from aftermarket High Flow Downpipe.

[5soko]

When did this issue arise? Maybe flash to stock?

[harris69]

What are signs and symptoms of a misfire? My car has slight rough idle that doesn't feel normal but besides that I don't get any CELs or any other symptoms.

[ssgm1x]

Originally Posted by harris69

What are signs and symptoms of a misfire? My car has slight rough idle that doesn't feel normal but besides that I don't get any CELs or any other symptoms.

Yea I'm not getting a check engine light either. Flashed to stock so I can troubleshoot and also in case I gotta bring it back to Bmw dealer so no tune right now. Not sure if I have a vacuum leak but boost/wastegate seem ok. I ran Ista " Rough running cylinder test " and t shows misfires across multiple cylinders after I re start the car. Also pre catalytic converter O2 sensor is reading 1.4 Volts and does not move. It should be reading .1v to .9v at idle....
26K miles on car. Brand New OEM Plugs and New Coils with (stock gap).
The other day was on the road and car backfired from the engine compartment. Was 89F and humid. Also Had the A/C on. Gave it about 30% throttle and it backfired..... A WTF moment......No CEL either.... How do I test injectors?

[harris69]

All of this is new to me so no idea.

[5soko]

Since plugs and coils are new...

Then i'd look into fueling system...

n55 fuel pump and injectors r pretty reliable.
Could start by looking into ISTA into fuel pressure at the rail is where it is suppose to be.

From there i would start swapping injectors or putting in new ones to see if misfires go away. There isn't any injectors tests i know of in ISTA.

Just to confirm, double check to run the vanos system test, i know u mentioned u did the relearn.

Do the same for the valcetronic.

Both play a big roll in idle.

Btw how long does this rough running idle last?
n55 engines r known to run a bit rough on hot restart for a few seconds

[ssgm1x]

Originally Posted by 5soko

Since plugs and coils are new...

Then i'd look into fueling system...

n55 fuel pump and injectors r pretty reliable.
Could start by looking into ISTA into fuel pressure at the rail is where it is suppose to be.

From there i would start swapping injectors or putting in new ones to see if misfires go away. There isn't any injectors tests i know of in ISTA.

Just to confirm, double check to run the vanos system test, i know u mentioned u did the relearn.

Do the same for the valcetronic.

Both play a big roll in idle.

Thanks for the suggestions. I think the injectors are expensive. $276 each. But will look into fuel system via Ista. I was kinda hoping my CEL would come on but I guess it's within threshold for now. My dealership sucks at troubleshooting a car when no CEL present. Figure I would diagnose myself for now.

This whole rough idle thing happened the day I did new plugs and coils. Have since changed plugs and coils 3 times with new ones and no resolve....Oem gap. Oem plugs. Oem coils.

[ssgm1x]

Originally Posted by 5soko

Since plugs and coils are new...

Then i'd look into fueling system...

n55 fuel pump and injectors r pretty reliable.
Could start by looking into ISTA into fuel pressure at the rail is where it is suppose to be.

From there i would start swapping injectors or putting in new ones to see if misfires go away. There isn't any injectors tests i know of in ISTA.

Just to confirm, double check to run the vanos system test, i know u mentioned u did the relearn.

Do the same for the valcetronic.

Both play a big roll in idle.

Btw how long does this rough running idle last?
n55 engines r known to run a bit rough on hot restart for a few seconds

I'm getting misfires in the misfire counter after every warm restart. Sometimes the idle even searches a bit.
Maybe my O2 sensors are mixed up ?
The Pre Cat O2 sensor (brown marking on connector)on left in pic and the Post Cat O2 sensor is on the right. Are these the correct positions ? They are connected properly but are they in the correct position on the Cat. Pics attached.

[5soko]

Originally Posted by ssgm1x

Reason I ask about position is because they are behaving like they are in the incorrect position. Pre Cat O2 sensor barely moves and post Cat O2 sensor cycles between .1 and .9.... Exact opposite of what they're supposed to do (I think)

Did this rough idle happen after the downpipe install?

Let me check my notes..

That is correct, without a cel most dealers will tell u, its fine lol.

Use "injector determination" in ISTA to see which injectors you need.. sounds like EU5 injectors and those r about 100 a piece with new seals and all.. oem..

[5soko]

The 02 senor with the grey wire shielding is the post cat sensor..

[ssgm1x]

Originally Posted by 5soko

The 02 senor with the grey wire shielding is the post cat sensor..

On my car the Grey O2 wire is hooked up to Before the Catalytic Converter. I guess the idiot that installed my Downpipe mixed them up.
I will try and post a pic for u. That would explain the rough idle then

[ssgm1x]

Originally Posted by 5soko

The 02 senor with the grey wire shielding is the post cat sensor..

Yup. You are correct. This is how it should be.
The VBand end is turbo side (pre Cat)
And mine are in backwards. Hence rough idle and backfires.....
Thanks for your help!!! Greatly Appreciated!!!!

[ssgm1x]

Originally Posted by ssgm1x

Reason I ask about position is because they are behaving like they are in the incorrect position. Pre Cat O2 sensor barely moves and post Cat O2 sensor cycles between .1 and .9.... Exact opposite of what they're supposed to do (I think)

Need some help, These Oxygen sensor Voltages dont look correct.....
Im pretty sure the Pre Catalytic Oxygen sensor is supposed to cycle between .1 Volts and .9 Volts (average. of .45 V)...
But my Pre Catalytic Oxygen sensor sits at 1.49 Volts and barely moves at idle. My after Catalytic voltage sits at about .6-.7 volts and barely moves at idle.
My Pre-Catalytic Air Ratio is .99 and my after Catalytic Air Ratio is .99
Can someone please confirm these values are Bad or Good. Im not an Oxygen sensor expert....fat from it....
Thank you.
I'm also getting O2 sensor "active" and then cycled to "inactive" back n forth. Once car warms up isn't it supposed to stay "active" ?

[yusufm786]

Originally Posted by ssgm1x

Yup. You are correct. This is how it should be.
The VBand end is turbo side (pre Cat)
And mine are in backwards. Hence rough idle and backfires.....
Thanks for your help!!! Greatly Appreciated!!!!

Seem to be having the same symptoms, but it's a mission to get access to the downpipe to verify the connections. Is it possible to just swop the plugs at the top, i.e. are the connections the same?

[MatthewLC]

I'm trying to chase down a similar problem.

I'm new to using ISTA. Does anyone know in which menu the Valvetronic and Vanos tests are?

[The Blimp]

Hey OP, did you ever work this out?

I have the same issues on the same cylinders (1, 3 & 4) and can’t figure out what the inpa values actually mean. No error codes but idle is garbage.

[CarCar15]

P11B0
P12A6

what could these be my reader has no description??