Car Running Rough after MHD Stage 1+ Tune

spitfun · Post by **spitfun** » Wed Jan 25, 2023 5:57 am

I flashed my car over the weekend with the MHD Stage 1+. Everything seemed to go fine-it said "successful' at the end and the car started right up. I took it out for the first ride today,let it warm up (about 200 degrees for the oil),I did a WOT to 6.5k in 2nd getting on the highway and hit 3rd-then the engine light came on and it ran rough and seemed like it was running on 5 cylinders,I babied it home and turned the car off. About an hour later I went back out and started her up and the engine light is off and she idles fines,you guys have any ideas how it fixed itself? The only other thing I did before that first drive was to install a larger intercooler,it seems like if it was a bad coil or spark plug it would still be running rough-although I did order new Eldor coils and 2 sets of spark plugs (OEM Bosch and NGK 1 step colder) that I will install to just start with new ones...

tiglon · Post by **tiglon** » Wed Jan 25, 2023 9:31 am

I would guess a coil. Exactly the same happened with mine after remapping.

B21 · Post by **B21** » Wed Jan 25, 2023 10:32 am

When you flash MHD v9 or V10 it does seem to find any issues with coils or plugs..

This happened to me on one coil…I replaced all the coils n plugs and narrowed the gaps and issue went away..

The misfire, engine light on, then reset when restarted is all standard N54 DME management logic..

As usual decent code reader will show which cylinder (s) are at fault.

spitfun · Post by **spitfun** » Wed Jan 25, 2023 10:43 am

I did go with v10,I figured why not put the latest version in. Thanks for the info...

B21 · Post by **B21** » Wed Jan 25, 2023 12:25 pm

spitfun wrote: ↑Wed Jan 25, 2023 10:43 am I did go with v10,I figured why not put the latest version in. Thanks for the info...

With 400 ish BHP and 650nm torque it’s pushing the physical and electrical limits of the stock components….

spitfun · Post by **spitfun** » Wed Jan 25, 2023 12:34 pm

Now you're scaring me... Should I drop down to stage 1? I only drive it on the street and an occasional autocross

B21 · Post by **B21** » Wed Jan 25, 2023 12:37 pm

spitfun wrote: ↑Wed Jan 25, 2023 12:34 pm Now you're scaring me...

Not really..it was a 300 BHP 450nm motor and with the 35is they pushed it to 335 ish BHP with an over boost taking it to 500nm…

So 400 BHP is 33% up on the ‘true’ reference line…also the MHD V10 version rolls a lot more torque in early which will put much more strain on plugs n coils…not to mention issues like LSPI etc…

spitfun · Post by **spitfun** » Wed Jan 25, 2023 12:42 pm

Stage 1 better choice?

B21 · Post by **B21** » Wed Jan 25, 2023 1:08 pm

Lesser tunes put lesser strain on components…

I’d suggest it’s just being more conscious of what’s happening in the engine…

Twin turbo N54s generate large amounts of torque low down..lugging the engine whilst asking for big torque induces greater strains on the engine..hence the rise of low speed pre ignition on turbo’d engines with auto boxes shifting to high gears at low rpm..

Personally if I’m ‘poodling’ I leave it in comfort mode and don’t prod the throttle too aggressively..makes more than adequate progress most of the time..

If I want to ‘press on’ I put the box in sport / manual mode and spin the engine a bit more…

Seems a bit like unnecessary concern for the engine..but if you had a NA car that was tuned then for sure you’d spin it to get more progress..

mcbutler · Post by **mcbutler** » Wed Jan 25, 2023 1:21 pm

spitfun wrote: ↑Wed Jan 25, 2023 12:34 pm Now you're scaring me... Should I drop down to stage 1? I only drive it on the street and an occasional autocross

NO go stage 2, perfectly fine on stock. I have enquired many times with tuning companies ref upgraded coil packs etc and they are all very clear that at 400/450 you are not even really near needing them.
My 35i has done around 6k on full MHD tune and full XHP map on the DCT, upgraded downpipes, intercooler etc and its more than enough... MHD can analyse your car as well, try doing a live data run, if the error reoccurs send the result to MHD, also try posting in on their FB page, they are very helpful and an absolute mine of highly qualified tuning brains...

B21 · Post by **B21** » Wed Jan 25, 2023 1:22 pm

Here are a few charts showing 35is stock vs V9 and V10 and effect of no filter etc.. enjoy..

B21 · Post by **B21** » Wed Jan 25, 2023 1:31 pm

You may want to look at this article and associated ones..good bed time reading..

https://bmwtuning.co/n54-tuning-guide-beginners/

spitfun · Post by **spitfun** » Wed Jan 25, 2023 1:45 pm

I just scanned the car,looks like misfire cylinder #4 was the culprit.

: 20230125_054457.jpg (164.17 KiB) Viewed 285 times

B21 · Post by **B21** » Wed Jan 25, 2023 1:50 pm

If you are getting a fresh set of plugs n coils thats the best move..just fit them and maybe close the plu gaps up a bit from stock..22 thou to 25 thou..you can start stock gaps at 30 thou and narrow till misfire ceases..each car is a seperate case at this level of tune..

Have you had the inlets de-coked or checked?

spitfun · Post by **spitfun** » Wed Jan 25, 2023 3:11 pm

What inlets?? I just bought this car a few months,excuse my ignorance. I have done the suspension so far,just getting to the engine. The car has 110k on it,so alot of components may be original...

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