Car Running Rough after MHD Tune

spitfun · 01-24-2023, 10:56 PM

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 for 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 was a bad coil or spark plug it would still be running rough-although I did order new Eldor coils and 2 sweets of sprak plugs (OEM bosch and NGK 1 step colder) that I will install to just start with new ones...

TCBTODD · 01-25-2023, 09:56 AM

I had a similar issue when a did a tune on mine. Ended up being the coils.

MRCW · 01-26-2023, 06:17 PM

Let us know miles, year...
On my 2013 35i I installed stage one several months ago. Has be flawless and pulls like a champ from about 3800

Lurcher · 02-22-2023, 08:24 PM

use the NGKs - gap at .20 or .22- Coils and plugs are wear itmes and the tune wants the best it can get.

The computer resets after shutoff, thus putting the bad coil back into the mix

ray7792 · 02-23-2023, 09:35 AM

Start with coils and plugs as you already suggested, most likely will fix it.

But in the unlikely event that it still occurs at WOT try logging for the rail pressure and see if its dropping randomly or all over the place at WOT, it could be your HPFP starting to go bad causing the misfire. Hopefully not but its common on these motors.

spitfun · 02-25-2023, 07:41 PM

I have since changed the coils and plugs and the problem has gone away. She runs great now.

MRCW · 02-26-2023, 12:20 PM

Quote:

Originally Posted by spitfun

I have since changed the coils and plugs and the problem has gone away. She runs great now.

Glad to hear that's what it was. Tunes can often exaggerate issues that are sometime not noticeable

etropic · 02-27-2023, 01:01 PM

Same experience this weekend. Misfires after 10 minutes of pushing on the Stage 1 tune, but factory is fine. Going to do plugs and coils.

01-24-2023, 10:56 PM	#1
spitfun Enlisted Member 5 Rep 43 Posts Drives: BMW Z4 M E89 Join Date: Oct 2022 Location: Michigan iTrader: (0)	Car Running Rough after MHD Tune 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 for 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 was a bad coil or spark plug it would still be running rough-although I did order new Eldor coils and 2 sweets of sprak plugs (OEM bosch and NGK 1 step colder) that I will install to just start with new ones...
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01-25-2023, 09:56 AM	#2
TCBTODD New Member 0 Rep 6 Posts Drives: 2016 BMW Z4 35is Join Date: May 2019 Location: Rocklin, CA iTrader: (0)	I had a similar issue when a did a tune on mine. Ended up being the coils.
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01-26-2023, 06:17 PM	#3
MRCW Enlisted Member 2 Rep 48 Posts Drives: Z4 35i X1 35i Join Date: Oct 2022 Location: Florida iTrader: (0)	Let us know miles, year... On my 2013 35i I installed stage one several months ago. Has be flawless and pulls like a champ from about 3800
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02-22-2023, 08:24 PM	#4
Lurcher Captain 71 Rep 676 Posts Drives: 2012 z4 Join Date: May 2013 Location: Buford, GA (right side of ATL) iTrader: (0)	use the NGKs - gap at .20 or .22- Coils and plugs are wear itmes and the tune wants the best it can get. The computer resets after shutoff, thus putting the bad coil back into the mix
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02-23-2023, 09:35 AM	#5
ray7792 Private 10 Rep 65 Posts Drives: '14 35is Join Date: Jan 2016 Location: NJ iTrader: (0)	Start with coils and plugs as you already suggested, most likely will fix it. But in the unlikely event that it still occurs at WOT try logging for the rail pressure and see if its dropping randomly or all over the place at WOT, it could be your HPFP starting to go bad causing the misfire. Hopefully not but its common on these motors.
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02-25-2023, 07:41 PM	#6
spitfun Enlisted Member 5 Rep 43 Posts Drives: BMW Z4 M E89 Join Date: Oct 2022 Location: Michigan iTrader: (0)	I have since changed the coils and plugs and the problem has gone away. She runs great now.
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02-27-2023, 01:01 PM	#8
etropic Registered 0 Rep 4 Posts Drives: BMW E89 Join Date: Jul 2021 Location: Phoenix iTrader: (0)	Same experience this weekend. Misfires after 10 minutes of pushing on the Stage 1 tune, but factory is fine. Going to do plugs and coils.
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