[Tiberius73]

I have a '07 E93 335i. I bought it new and have owned it since. 71k miles.

I got it tuned in 2012, custom tune, with 6k miles on it. I did pretty much the FBO with big FMIC, DCI, charge pipe, CAT-less DP + original exhaust, turbo inlet, turbo outlet, catch-can. Original BOV. I service the car very regularly even though it doesn't go out so very much. The intakes are spotless.

The custom tune was done on the dyno and put out 375whp. I drove it like that since 2012. Never had any problems.

Due to a mishap, the custom tune was wiped by someone I now like a lot less than before. But what's done is done. I bought the MHD Stage2+ tune, which should make more or less the same power as the custom tune on 93 OCT/98 RON. We put that on and went for a drive. First WOT from 3k rpm and it misfired. CEL. Limp mode, engine shaking. We checked the settings and made sure everything was right. Looked right, but we then put the Stage2+ for 91 OCT/95 RON and first WOT and misfire.

We put Stage 1+ on and...again misfire, but not right away. I went WOT at 3krpm in 4rd and revved out 3rd gear, it shifted from 3rd to 4th and then instantly misfired, limp mode. We put Stage 1 on and again...misfire pretty much exactly like on Stage 1+.
We did all of the above 2 times and each time it was pretty much exactly the same.

Note that when we started all the above the engine was fully warmed up. Oil temp at 110C, so almost full operating temp.
We scratched our heads about the misfires. All were on Cylinder 4 or 2 with Cylinder 4 being in every single pull and Cylinder 2 only happening on Stage 2+ and 1+.

Well, we checked the coils and plugs, they all looked okay. We swapped them around Still cylinders 2 and 4. So, we're thinking injectors...HPFP maybe too, or LPFP. But fuelling rather than ignition.

It's too late to buy new coils/plugs so I go home. Now the engine temp is down...oil temp is 80C. On a straight I go WOT with the Stage 1+ that is left on there and ... it pulls 2nd, 3rd, 4th and into 5th. A nice big pull with no hiccups. The section of the road ends (junction) and pass the junction and WOT again...in 3rd gear at 4.5k rpm: misfire. Diagnostic says "misfire Cyl 4." and also on #2. I reset and just drive home slow.

Now this was a Friday...on Monday I have an email from the tuner who did my tune 10 years ago. He found my old tune and sent it over for us to try and put back on. Sure enough, Monday evening we put that old tune back on. I take the car our carefully, cautiously and go WOT. Car pulls perfectly, like before. And it pulls very much more than the Stage1+ from MHD, as it should. I do this 5, 6 more times. It just pulls and pulls through all the gears.
So..we go back and put MHD Stage 2 on and...first WOT it misfires. Cyl 4 + 2.

The custom tune goes right back on and we try again. No misfire. Works just fine.

What on earth is going on? I mean.. I can drive around with the custom tune, so I'm okay, but this is baffling. What could be going on?

[Saif2018]

Originally Posted by Tiberius73

I have a '07 E93 335i. I bought it new and have owned it since. 71k miles.

I got it tuned in 2012, custom tune, with 6k miles on it. I did pretty much the FBO with big FMIC, DCI, charge pipe, CAT-less DP + original exhaust, turbo inlet, turbo outlet, catch-can. Original BOV. I service the car very regularly even though it doesn't go out so very much. The intakes are spotless.

The custom tune was done on the dyno and put out 375whp. I drove it like that since 2012. Never had any problems.

Due to a mishap, the custom tune was wiped by someone I now like a lot less than before. But what's done is done. I bought the MHD Stage2+ tune, which should make more or less the same power as the custom tune on 93 OCT/98 RON. We put that on and went for a drive. First WOT from 3k rpm and it misfired. CEL. Limp mode, engine shaking. We checked the settings and made sure everything was right. Looked right, but we then put the Stage2+ for 91 OCT/95 RON and first WOT and misfire.

We put Stage 1+ on and...again misfire, but not right away. I went WOT at 3krpm in 4rd and revved out 3rd gear, it shifted from 3rd to 4th and then instantly misfired, limp mode. We put Stage 1 on and again...misfire pretty much exactly like on Stage 1+.
We did all of the above 2 times and each time it was pretty much exactly the same.

Note that when we started all the above the engine was fully warmed up. Oil temp at 110C, so almost full operating temp.
We scratched our heads about the misfires. All were on Cylinder 4 or 2 with Cylinder 4 being in every single pull and Cylinder 2 only happening on Stage 2+ and 1+.

Well, we checked the coils and plugs, they all looked okay. We swapped them around Still cylinders 2 and 4. So, we're thinking injectors...HPFP maybe too, or LPFP. But fuelling rather than ignition.

It's too late to buy new coils/plugs so I go home. Now the engine temp is down...oil temp is 80C. On a straight I go WOT with the Stage 1+ that is left on there and ... it pulls 2nd, 3rd, 4th and into 5th. A nice big pull with no hiccups. The section of the road ends (junction) and pass the junction and WOT again...in 3rd gear at 4.5k rpm: misfire. Diagnostic says "misfire Cyl 4." and also on #2. I reset and just drive home slow.

Now this was a Friday...on Monday I have an email from the tuner who did my tune 10 years ago. He found my old tune and sent it over for us to try and put back on. Sure enough, Monday evening we put that old tune back on. I take the car our carefully, cautiously and go WOT. Car pulls perfectly, like before. And it pulls very much more than the Stage1+ from MHD, as it should. I do this 5, 6 more times. It just pulls and pulls through all the gears.
So..we go back and put MHD Stage 2 on and...first WOT it misfires. Cyl 4 + 2.

The custom tune goes right back on and we try again. No misfire. Works just fine.

What on earth is going on? I mean.. I can drive around with the custom tune, so I'm okay, but this is baffling. What could be going on?

Which Version OTS map is it misfiring on?

Do the plugs and coils if you haven't done it recently, and use your custom map, always keep a backup and don't bother with OTS maps, if the custom tune is running fine.

[Tiberius73]

Originally Posted by Saif2018

Which Version OTS map is it misfiring on?

Do the plugs and coils if you haven't done it recently, and use your custom map, always keep a backup and don't bother with OTS maps, if the custom tune is running fine.

I went for the MHD tune because someone zapped my custom tune when they weren't paying attention. I didn't have a backup of it... The custom tune was 10 yrs prior and when I called they said they didn't have it any more. Well, they ended up finding it a few days later but in the mean time, having heard them tell me they don't have it after 10 years, I'd gotten the MHD tune.

The Misfires are on all MHD tunes: Stage 1, Stage 1+, Stage 2, Stage 2+. Always Cylinder 4 and also usually Cylinder 2 (but not always).

Coils are new (300 miles). Spark plugs have maybe 500 miles on them. Moving them around doesn't change the problem on the MHD tunes.

Custom tune seems to run fine.

What mystifies us is that the custom tune is around 375whp on a hot day with 93 OCT/98 RON pump gas. It's not the fastest car ever, but it really pulls nice for a 15 YO car. The butt-dyno is very happy. The MHD Stage 1 tune is really a lot slower, has quite a bit less power and torque, yet it produces misfires.

[CarAbuser]

Impossible to tell without any logs. First thought was that the custom tune is less aggressive than the MHD OTS tunes but without a log of either tune it's purely guess work.

[Maxboosteric]

+1 miss fire turn them down and they stop. Mhd more aggressive then your current but like stated a datalog needed. Roll with your old tune sounds like you were happy.

[Dave92N54]

The MHD map is most likely much more aggressive. Tuning on these cars is vastly different now than 10 years ago.

Curious, have you cleaned the intake valves? Sounds like it should be time.

[Dave92N54]

Originally Posted by TerminatorStout

If the intakes are spotless, and you have swapped both coils AND sparkplugs (gap problems, very sensitive), then I think you should search about MOSFETS in DME?? I remember reading a thread about it. It's got to be either that or the injectors I would assume. I put the stamp that I am just learning this engine as I am trolling all the threads, so I hope this helps.

MOSFETs have a very telltale sign. You will see a misfire on all 3 cylinders in one bank i.e. 1-3 or 4-6. The misfire codes will also be accompanied by a 30BA or 30BB code.