Datalog BMW 135i Cold Start Rough Idle (fine when JB4/MHD removed)

[Phillstine]

Hi Guys,

I've been having a problem with my car for a while and have replaced loads of things to no avail.

On starting only when cold and left for over 24 hours the first start up is rough and stumbles and misfires badly for 10 seconds.

I've replaced Injectors to Index 12
HPFP replaced
Low pressure Sensor replaced
Sparkplugs replaced
Coil replaced
Vanos Solenoids replaced
Inlets Walnut Blasted
New Turbos

I don't get any codes, I notice that when starting it's fine until the JB4 wakes up (Needle Sweep) then starts running poorly so I removed the JB4 and it would start fine every time. I then Mapped the car with MHD and the problem is back, flash back to stock starts perfect again.

Is there something in the fuel tables on MHD/JB4 that effects start up different to stock?

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Thanks you in advance for your help!

 

[KClemente]

Is your cold start still enabled? Your timing is hitting deep into the negatives which will slow the idle down and then the PID will try and raise timing and then get caught into a loop.

What spark plugs are you running and with what gap?

 

[Phillstine]

I currently have cold start delete running as it stops the roughness being so aggressive until you put it into gear (bringing the rpm up). Without cold start delete it will sometimes be so bad it will stall.

The plugs are just the standard Bosch plugs, no adjustments to the gap. Although I had the problem before I changed the plugs and it ran fine on the old plugs for a good few thousand miles.

Thanks

 

[BloodyZ4]

Can you log Laufunruhe?

I had a similar issue, turned out one of my new index 12's was faulty.

That way you can identify which cylinders are causing the issue. Then start with swapping plugs/coils on that cylinder and see if it moves to the swapped one. If not it’s the injector.

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[Phillstine]

Is that the rough running element in INPA? Also if it was an injector wouldn't that still exhibit on Stock map? I have a video of how it behaves with the JB4 but I'm not sure the forum likes YouTube Links

 

[SLOWESTN54]

Try turning cold start reduction off then see how it starts up.

 

[Phillstine]

Happy to try that but as it did it with a JB4 (no cold start delete) I'm not so sure it'll do much.

 

[colo_evo]

Try turning cold start reduction off then see how it starts up.

Had a similar issue with mine and this fixed it.

 

[SLOWESTN54]

Had a similar issue with mine and this fixed it.

1+ when it got colder my car hated cold starts with cold start noise reduction enabled in MHD.

 

[SlowE93]

Is that the rough running element in INPA? Also if it was an injector wouldn't that still exhibit on Stock map? I have a video of how it behaves with the JB4 but I'm not sure the forum likes YouTube Links

Fuck what the forum likes and post it if you want assistance.

 

[Phillstine]

By that I mean the thread kept getting deleted

JB4 Issue? - YouTube - Despite the title the issue isn't specific to JB4 the video is my car but not my YouTube.

 

[SLOWESTN54]

By that I mean the thread kept getting deleted

JB4 Issue? - YouTube - Despite the title the issue isn't specific to JB4 the video is my car but not my YouTube.

Sir your car is very unhappy. It only runs well in limp mode indicating the cars going into open loop most likely. Did you check out what the code was?

 

[Phillstine]

It has only ever produced a code once and wasn’t helpful. It’s also only when starting up. The car runs and pulls perfectly fine after you tap the throttle or leave it to sort itself.

Anytime you run the car subsequent to a “cold start” it runs perfect not so much as a hint of a misfire.

Once the JB4 was removed it never caused a problem, once MHD is set back to stock map, starts up perfect everytime.

The start up on the video is fine until the JB4 activates.

 

[SlowE93]

Sir your car is very unhappy. It only runs well in limp mode indicating the cars going into closed loop most likely. Did you check out what the code was?

Limp is open loop

 

[SlowE93]

Jb4 log of start up would / should shed some light
Maybe wrong firmware ? Or settings ?

 

[SLOWESTN54]

Limp is open loop

Edited sorry i meant open

 

[Phillstine]

Jb4 log of start up would / should shed some light
Maybe wrong firmware ? Or settings ?

The JB4 has been removed and the above log was taken on Startup via MHD, I also removed the Cold Start off and it’s not made any difference.

 

[carabuser]

The JB4 has been removed and the above log was taken on Startup via MHD, I also removed the Cold Start off and it’s not made any difference.

So it's perfect when no tune is installed?

What flash options do you have selected for MHD?

 

[Phillstine]

Yep no issues when no tune or JB4 installed.

With MHD I just use the same settings I've used on my other cars
Stage 2 98 Ron (99 Fuel always used)
Aftermarket DPs
Cold start noise reduction (turned back on, no longer stumbles at idle only when selecting gear straight away 2 seconds after start up)

So seems to happen when reaching a certain RPM/Load after initial cold start

 

[carabuser]

The car is struggling to keep RPMs on target, that's why the throttle and timing are both all over the place. I have no idea why MHD would make things worse. My initial though was that you had some strange settings for coils or TMAP sensor in MHD but if your flash options are just after-maket DPs then clearly something else is causing it.

It's hard to make any suggestions because you seem to have already changed most common culprits.

Looking at the rough running values in INPA might be able to pinpoint the problem down to 1 cylinder as @BloodyZ4 mentioned.

I'd return the car to stock for a longer period to make certain that it doesn't happen at all when stock. Is the idle completely smooth when stock?