29DC after hitting rev limiter ?

[studio54]

Hello,

I was doing some WOTs on expressway and despite having taking the habit to shift at 5800-6000, this time I was enjoying the WOT and didn't take attention and hit rev limiter in 3rd gear at around 170+kph and 7000 rpm for one second (I sometimes hit the limiter in 1st or 2nd with no problem). It backfired during the rev limiter phase like it does normally cause I have the shiftbog tq limit 2048 option ticked in MHD which turn the stock soft limiter into a kind of hard limiter, so when rev limiter is hit, it backfires multiples very fast in a row until let off.
A long medium curb was arriving when I let off, so during the curb I wasn't on throttle, when I wanted to give it back after the curb, then the car was acting like it has a misfires and sound horribly throatier/weird or something.

No CEL.
I stopped on a parking and idle was bouncing a bit from 600 to 800, so I stopped the engine and restarted, then it was all fine again, stable idle and continued to WOT without any issues (while not hitting rev limiter in 3rd ).

When back home, I could read codes, and 29DC was in the history list.

Car was running a 1/4 tank, with a kind of E30 mixture. It's my week-end car, sometimes not driven for 2 weeks.
I give those details cause I know E85 sitting long time is bad and could mess with water/humidity and with 1/4 of tank maybe LPFP pressure is not top notch ?
(and sometimes the devil is in the details..)

Is 29DC exclusively related to injection/injectors and/or fuel (LPFP/HPFP) ? or could it be related to spark/coils too ? or tune (self custom) ?
(Any chance the DME could trigger the 29DC when STFT maxed out for example ?)

I know it will be difficult to diagnose without logs at first, but I will try to investigate/log and reproduce ASAP, what's important to log for this problem ?

Thanks all

 

[SlowE93]

Hello,

I was doing some WOTs on expressway and despite having taking the habit to shift at 5800-6000, this time I was enjoying the WOT and didn't take attention and hit rev limiter in 3rd gear at around 170+kph and 7000 rpm for one second (I sometimes hit the limiter in 1st or 2nd with no problem). It backfired during the rev limiter phase like it does normally cause I have the shiftbog tq limit 2048 option ticked in MHD which turn the stock soft limiter into a kind of hard limiter, so when rev limiter is hit, it backfires multiples very fast in a row until let off.
A long medium curb was arriving when I let off, so during the curb I wasn't on throttle, when I wanted to give it back after the curb, then the car was acting like it has a misfires and sound horribly throatier/weird or something.

No CEL.
I stopped on a parking and idle was bouncing a bit from 600 to 800, so I stopped the engine and restarted, then it was all fine again, stable idle and continued to WOT without any issues (while not hitting rev limiter in 3rd ).

When back home, I could read codes, and 29DC was in the history list.

Car was running a 1/4 tank, with a kind of E30 mixture. It's my week-end car, sometimes not driven for 2 weeks.
I give those details cause I know E85 sitting long time is bad and could mess with water/humidity and with 1/4 of tank maybe LPFP pressure is not top notch ?
(and sometimes the devil is in the details..)

Is 29DC exclusively related to injection/injectors and/or fuel (LPFP/HPFP) ? or could it be related to spark/coils too ? or tune (self custom) ?
(Any chance the DME could trigger the 29DC when STFT maxed out for example ?)

I know it will be difficult to diagnose without logs at first, but I will try to investigate/log and reproduce ASAP, what's important to log for this problem ?

Thanks all

Sounds like it may have misfired from slamming limiter ?
I would not try to reproduce, I would try to avoid doing it again

 

[studio54]

Sounds like it may have misfired from slamming limiter ?
I would not try to reproduce, I would try to avoid doing it again

I think it felt the same as misfires cause when 29DC is triggered, one or multiples injectors seems to be disabled until restart from what I read online.

I already had misfires in the past when one of my coils was bad, and I got a CEL + a misfire code with the specific cylinder number concerned. This time is different, no CEL, just 29DC, it's an injection cutout, however the DME did not precised which injector which point it might a general problem with fuel starvation (will check low and high fuel pressures in log) or maybe I need to revise my fuel scalar tables with STFT that I will log to see it maxes out.

I cannot count times I hit rev limiter these last years (1st, 2nd or even 3rd faintly though, this time 1 second :/ ), that's why it's surprising me, made me believe there is probably something that might be wrong : fuel mixture, injector(s), LPFP or HPFP, tune.

Or it could be like you said as well, maybe the rev limiter phase is asking too much fuel speaking, and DME triggered the 29DC.

What to log ?
Fuel mode, LPFP/HPFP, STFT/LTFT, AFR should be ok?

 

[SlowE93]

I don't have MHD so not sure what can and can not be logged. I would log anything fuel related though.