[NEED5MIL]

Just got my car back from the shop after getting a walnut blast and transmission service, car drove perfect for about 30mins before I got a transmission malfunction light then limp mode.(sidenote: tranny malfunction error came on once before I got the walnut blast) So I turn the car off n back on and ever since the car has had a weird rough idle only when I’m parked or coming to a stop or at a redlight almost like it’s misfiring but it isn’t. Once I’m driving it’s pretty smooth.

I checked to see if the car was throwing any codes which it isn’t. The car has about 135k miles and I was running Stage1 MHD & Alpina Tune. I downtuned it to Stage0 to see if the problem would still be there and it still was, the idle has gotten a taaaad bit better since down tuning.

Is their any “break in” period for walnut blast? Lol

I’m leaning towards bad injectors but I’d think the car would throw codes if that was the case. Just seen a YouTube video and this guy was having the same symptoms and solved his problem with a new MAP sensor

Also about the transmission malfunction, it didn’t start slipping until I went MHD stage 1. does this mean I need a whole new tranny or maybe just a stage 2 clutch?

Anyone else have this problem after MHD tune or rough idle after Walnut blast? If so what’d you do fix to get rid of it
Any Info helps!

[Saif2018]

Originally Posted by NEED5MIL

Just got my car back from the shop after getting a walnut blast and transmission service, car drove perfect for about 30mins before I got a transmission malfunction light then limp mode.(sidenote: tranny malfunction error came on once before I got the walnut blast) So I turn the car off n back on and ever since the car has had a weird rough idle only when I’m parked or coming to a stop or at a redlight almost like it’s misfiring but it isn’t. Once I’m driving it’s pretty smooth.

I checked to see if the car was throwing any codes which it isn’t. The car has about 135k miles and I was running Stage1 MHD & Alpina Tune. I downtuned it to Stage0 to see if the problem would still be there and it still was, the idle has gotten a taaaad bit better since down tuning.

Is their any “break in” period for walnut blast? Lol

I’m leaning towards bad injectors but I’d think the car would throw codes if that was the case. Just seen a YouTube video and this guy was having the same symptoms and solved his problem with a new MAP sensor

Also about the transmission malfunction, it didn’t start slipping until I went MHD stage 1. does this mean I need a whole new tranny or maybe just a stage 2 clutch?

Anyone else have this problem after MHD tune or rough idle after Walnut blast? If so what’d you do fix to get rid of it
Any Info helps!

I doubt you need another tranny or even clutch pack,

I'm not sure if MHD checks TCU codes, can you use INPA or Protool to check codes?

When you say you serviced the transmission, did you replace sleeves, seals, transmission Solenoids and Pan+Oil?

When were the plugs and coils done?

[E93Dude]

I walnut blasted my 07' 335 a few months ago, and also had a slightly rough idle for a few weeks/couple hundred miles until it smoothed out. I suspect it had to do with the ECU recalibrating to the new airflow paradigm. Interestingly, even in that initial rough idle break-in period, I noticed better gas mileage once the car was warmed up. I'd give it some time to see if things smooth out.

The MAP sensor should be cleaned since its in the same airflow as the recirculated fuel/oil/air mixture from the PCV system. Its located on the top of the plastic manifold assembly that had to be removed to do your walnut blast. The MAP can be removed from the top of the intake manifold by with a couple of screws and cleaned with cheap MAP/MAF cleaner from any autoparts store. With 135K on your odometer, you should definitly clean it.

[Bradn54]

I’d check the bolts on your inlet, could be a little
Leak, did they change the manifold gaskets after walnut blasting? Your transmission could be low o oil as when u change the oil you have to cycle gears to get the correct oil level, u can’t just drain it n top it up! With mhd you can reset ecu patameters so it learns again, reset adaptions on the app! Hope this helps

[Bimmer_Bro]

MHD won't read tcu codes. To be honest I would ditch Alpina and switch to xhp. It's far superior in every way possible. You can then use the xhp app to scan for transmission related codes.

[Bimmer_Bro]

Originally Posted by E93Dude

I walnut blasted my 07' 335 a few months ago, and also had a slightly rough idle for a few weeks/couple hundred miles until it smoothed out. I suspect it had to do with the ECU recalibrating to the new airflow paradigm. Interestingly, even in that initial rough idle break-in period, I noticed better gas mileage once the car was warmed up. I'd give it some time to see if things smooth out.

The MAP sensor should be cleaned since its in the same airflow as the recirculated fuel/oil/air mixture from the PCV system. Its located on the top of the plastic manifold assembly that had to be removed to do your walnut blast. The MAP can be removed from the top of the intake manifold by with a couple of screws and cleaned with cheap MAP/MAF cleaner from any autoparts store. With 135K on your odometer, you should definitly clean it.

Just for clarification: the sensor on the charge pipe is a map sensor. Cleaning it does nothing as they sense pressure.

The one you are referring to is a Maf sensor on the intake manifold. Yes cleaning them can help smoothness. Worth a shot.

[E93Dude]

Originally Posted by Bimmer_Bro

Just for clarification: the sensor on the charge pipe is a map sensor. Cleaning it does nothing as they sense pressure.

The one you are referring to is a Maf sensor on the intake manifold. Yes cleaning them can help smoothness. Worth a shot.

The N54 does not have a Mass Air Flow (MAF) sensor. It has a Manifold Air Pressure (MAP) sensor which is, by definition, always on the intake manifold. It measures the mass (not velocity/flow) of air molecules just before getting sucked into the cylinder. Its a final ECU check before it decides on air/fuel mix since the ECU wants to know the mass, not flow, of air to calculate the proper mix.

What you are talking about on the charge pipe is the (boost) "pressure sensor" which is part of the feedback loop with the turbos that help the ECU understand how well they are compressing air.

Cleaning both sensors with MAF cleaner can help, but its really the MAP on the intake manifold that is important to clean since the PCV system recirculates crankcase vapors back into the engine after the sensor on the charge pipe.

These two links from RealOEM.com are worth a look to visualize:
https://www.realoem.com/bmw/enUS/sho...diagId=11_3973

https://www.realoem.com/bmw/enUS/sho...diagId=13_1185

[mweisdorfer]

Did you check all of your vacuum lines?