[stuartbrown.e90]

So next week I will be installing the VRSF catless downpipes onto my n54 and tuning it to stage 2+. I currently have the intakes, charge pipe, and 5.5” intercooler on the MHD stage 1+. I will also be putting in new plugs and coils before the downpipes just to be safe. I had noticed random misfires using the v9 map from MHD. Does anyone know the best version to use or has had luck with one over the other?

[acidbbg]

I’m new to the BMW scene but have worked on turbo cars over 20 years. Direct injection turbo cars for over 15 years.

About the version of map for MHD make sure you select the newest version and select the correct octane and stage for the map to match your car.

As power levels goes up weak links start to appear. Adding more power mods will increase boost, timing, power causing those weak links to appear more frequently.

I would hold up on adding more mods until you address the cylinder miss firing issue.

good on you to swap out the spark plugs and coil packs. If you are any good with a wrench swap the spark plug and coil (from cylinder that’s misfiring) with one that not and see if the issue follows. If the miss fires still happening on the same cylinder then it’s unlikely the plug and coil are causing the problem. After that it’s likely to be one of 2 thing. Clogged/leaky injector or carbon build up on intake valves due to car being GDI. You may need to do walnut blasting.

Also, make sure to try fuel system cleaner (Techron, BG44k, etc). Also, I’ve had some success with crc gdi intake valve and turbo cleaner and or seafoam but you need to spray into throttle body/hose that feeds into the intake manifold to loosen up the carbon build up. You’ll need a 2nd person to start the car and gently apply throttle make sure the car doesn’t stall out. you slowly dip the hose into the cleaner and have some one gently applying gas pedal to keep the car from stalling. Do it slowly to avoid hydro locking the motor.

Also you can try 2-3 gallons of e85. Should help with clogged injectors and increase the cooling effect in the cylinder while also increasing the octane a few points.

I personally fill with Top Tier gas, 2-3 gallons of e85 every fill. I will be going meth injection soon.

Many of the people who I talked to/worked on their cylinder misfire issue (GDI turbo) needed walnut blasting to fix the issue. Had a mechanic friend who worked at VW dealership had to do a walnut blast to fix as nothing else addressed the issue. He told me lots of short drives and cheap gas will cause build up much faster.

Good luck and be sure to chime back in if/when you get it fixed.

[iqraceworks]

Originally Posted by stuartbrown.e90

So next week I will be installing the VRSF catless downpipes onto my n54 and tuning it to stage 2+. I currently have the intakes, charge pipe, and 5.5” intercooler on the MHD stage 1+. I will also be putting in new plugs and coils before the downpipes just to be safe. I had noticed random misfires using the v9 map from MHD. Does anyone know the best version to use or has had luck with one over the other?

Have you checked to see if any of your injectors are leaking? Leaking injectors can cause all types of issues.

[stuartbrown.e90]

Originally Posted by acidbbg

I’m new to the BMW scene but have worked on turbo cars over 20 years. Direct injection turbo cars for over 15 years.

About the version of map for MHD make sure you select the newest version and select the correct octane and stage for the map to match your car.

As power levels goes up weak links start to appear. Adding more power mods will increase boost, timing, power causing those weak links to appear more frequently.

I would hold up on adding more mods until you address the cylinder miss firing issue.

good on you to swap out the spark plugs and coil packs. If you are any good with a wrench swap the spark plug and coil (from cylinder that’s misfiring) with one that not and see if the issue follows. If the miss fires still happening on the same cylinder then it’s unlikely the plug and coil are causing the problem. After that it’s likely to be one of 2 thing. Clogged/leaky injector or carbon build up on intake valves due to car being GDI. You may need to do walnut blasting.

Also, make sure to try fuel system cleaner (Techron, BG44k, etc). Also, I’ve had some success with crc gdi intake valve and turbo cleaner and or seafoam but you need to spray into throttle body/hose that feeds into the intake manifold to loosen up the carbon build up. You’ll need a 2nd person to start the car and gently apply throttle make sure the car doesn’t stall out. you slowly dip the hose into the cleaner and have some one gently applying gas pedal to keep the car from stalling. Do it slowly to avoid hydro locking the motor.

Also you can try 2-3 gallons of e85. Should [...]

We have tried switching around the coils/plugs to see if the misfires would track with it, but the misfires are always on different/multiple cylinders. I have not tested my injectors to see if they are leaking or not but I am also planning to run some techron through this week before the downpipes as well as probably run an e85 mix for a short while after to maximize the cleanliness of the injectors etc.

[lowrydr310]

Like acidbbg said, hold off on any different tunes until you get the misfire resolved.

It might just be as simple as old worn out plugs. An old N52 powered 325i that I used to own started randomly misfiring, and it ended up being plugs that were severely worn.

I disagree with adding any E85 to the fuel just yet. In Tennessee you should be able to find 93 octane easily, so I'd suggest with flashing one of the MHD Stage 0 tunes (V10) and running a tank of 93 octane to see if you still have the misfire. I'm personally not a fan of any fuel system additives. I've tried several of them many times over many cars I owned and never really noticed any difference. There's definitely a benefit of ethanol blends, but not just yet until you get the misfire sorted. Even then, you'll need the correct tune for it.

When was the last time you had the intake valves walnut blasted?

Can you double check your DME version? I believe 2009+ cars had MSD81 which doesn't suffer from the MOSFET issue that MSD80 has, in which case you can rule that out easily as the cause of any misfires.

Beyond that, it might just be the injectors. Do you know what injectors you currently have installed?

You're on the right track with the diagnosis. Spark plugs and coils are a good start. Regarding your original question, I don't think there's any version of MHD OTS maps that are specifically prone to random misfires; there may be some other issues with throttle closure or other minor differences in boost limits by RPM, but I'm not aware of any misfire problems.

[stuartbrown.e90]

I have only owned the car for around a year now and have not had it walnut blasted. It has around 107k miles on it right now and i’m not sure if the previous owner ever had it done either, so it is probably due for one pretty soon. The injectors I have in the car are index 11 and I feel like those are usually fairly reliable. But we can’t rule them out completely because they’re still not index 12s.
The thing that is so strange about the misfires is when they show up. The car is almost always completely fine and runs smoothly on startup and for the first 15-20 minutes or so of driving, and then whenever I come to a stop and the car idles it will misfire and shake a little bit. But as soon as I give it gas or drive there are no misfires and the car doesn’t jump at all upon acceleration. Really hoping that the plugs and coils fix the issue.

[lookalikehuuh]

FYI just because injectors are index 12s doesn't mean they are good... or don't leak or fail. They are just a bit more reliable than prior versions but not something that will somehow guarantee an issue free fueling system.

Can you give us more information on when the misfire starts? does it start when you are heavy into the boost/engine RPM or just randomly like while you are cruising around?

It might be helpful to grab a log of the car when you notice the misfire. I once had a really weird misfire that turned out was due to damaged seals and missing decouplers because apparently my dealership was manned by idiots when I had the injector recall completed.

[stuartbrown.e90]

Originally Posted by lookalikehuuh

FYI just because injectors are index 12s doesn't mean they are good... or don't leak or fail. They are just a bit more reliable than prior versions but not something that will somehow guarantee an issue free fueling system.

Can you give us more information on when the misfire starts? does it start when you are heavy into the boost/engine RPM or just randomly like while you are cruising around?

It might be helpful to grab a log of the car when you notice the misfire. I once had a really weird misfire that turned out was due to damaged seals and missing decouplers because apparently my dealership was manned by idiots when I had the injector recall completed.

Yeah so the car is usually totally fine on startup, even on cold starts. Then after driving around for 15 or so minutes, when the car comes to a stop on it will begin to misfire. There are never any CELs or service engine soon lights, it just shakes a little bit. The RPM doesn’t fluctuate it just stays in the same spot, but the car feels like it shakes a little from side to side. The strange thing is whenever I give it throttle or start driving again there is no noticeable misfire/jumping that I can feel. It accelerates perfectly smoothly only when I come to a stop after sitting for around 10-15 seconds it will start misfiring. Last time I drove to school, by the time I got there it was misfiring so I just took a quick log of the idle in the parking lot. I’ll attach it below as well as a hard pull to around 5k in 3rd on the highway.
https://datazap.me/u/stuartbrown54/m...0&data=3-14-19
https://datazap.me/u/stuartbrown54/3...og=0&data=3-14