[Bimmerlife35]

Okay so just yesterday my car has started to stutter, mods I have are jb4 with mhd backend, dp’s, dci, and full straight pipe. it Doesn’t matter if I’m idling, driving normal, or wide-open throttle there always this stutter that happens id say maybe 2-3 times a minute, it’s like it looses power, or something with fuel delivery?, i don’t really now how to explain it well, I can’t post a video on YouTube if that would help anyone. I know the injector on cylinder 1 is leaking but it has been for 4 months so I don’t see that being the problem. I’ve checked spark plugs, coils are good, no codes what so ever besides the DME telling me it had detected Dp’s, and I’ve cleaned the vanos selonoids. I can’t do any data logging because my tablet for some reason never wants to connect to the jb4 rev 3 kit but from a log I did 2 weeks ago said that my LPFP got down to 51 for about 2 seconds, could that be it? Could it be o2 sensors? Intake carbon build up?

Please let me know if anyone has had this happen before or knows what I can fix! This is driving me nuts

[skirmozas]

Well, I think plenty of people on these forums had similar problems, so did I. But I'm just not sure what exactly fixed it or what the actual combination of things that did was. If we're talking about the same problem, which I would describe a hiccup at idle (barely noticeable dive in RPM's and hiccup only audible from outside, like the car skipped a single beat), then that's what I did and it got better. I think it idles smoother, but it's hard to tell if I just got used to it:

1. Backend flashed the car with BMS pump flash. It felt like it helped a little, but I could still hear the hiccups on occasions.
2. Replaced VC, spark plugs and injectors. VC was cracked so the spark plugs and injectors were deep in oil, didn't seem to affect the coils though. I did them all at the same time, it was convenient. Now after this, considering my needs for perfection are pretty humble, I would say the car started idling properly. I could hear something very similar to it on cold starts only, maybe once or twice in the first 30 seconds after the car has been started. Not very noticeable or very audible later.
3. Walnut blasted intake valves some time later. When inside, one can think that the car is not even on when you're coasting in neutral or just standing at the traffic light. Still the same cold start I would say. Nonetheless, I consider walnut blast to be the 2nd best "mod" for power gains in cheap and common hardware changes, right after the dpipes. The car runs so much smoother on WOT and seems predictably and extensively powerful. And of course, the sound of air filters sucking so much more air than they used to before. And this is just the point, where you realize that you really need a proper intercooler and inlets.

Back to the topic, I don't have access to E85, which probably makes our cases slightly different. E85 could be somewhat related to your problem. Other than that, we have very similar mods (except for straight exhaust), which makes this an interesting case to me too

Good luck troubleshooting the problem, hope you can find a fix for it.

[Vorsprung_CJB]

Grab a log of the issue when you can. You can get a full log of regular driving by going to Logging - X Axis - (uncheck) Heavy Throttle Only. Not sure where the option is on the mobile version but should be similar. Tough to diagnose otherwise. Could be injector, fuel pump, O2 sensors, tuning, etc.

[TDLI]

Originally Posted by skirmozas

2. Replaced VC, spark plugs and injectors. VC was cracked so the spark plugs and injectors were deep in oil, didn't seem to affect the coils though. I did them all at the same time, it was convenient. Now after this, considering my needs for perfection are pretty humble, I would say the car started idling properly. I could hear something very similar to it on cold starts only, maybe once or twice in the first 30 seconds after the car has been started. Not very noticeable or very audible later.
3. Walnut blasted intake valves some time later. When inside, one can think that the car is not even on when you're coasting in neutral or just standing at the traffic light. Still the same cold start I would say. Nonetheless, I consider walnut blast to be the 2nd best "mod" for power gains in cheap and common hardware changes, right after the dpipes. The car runs so much smoother on WOT and seems predictably and extensively powerful. And of course, the sound of air filters sucking so much more air than they used to before. And this is just the point, where you realize that you really need a proper intercooler and inlets.

Great advice!

To OP, I would start by trying to clean your TMAP and MAF sensors. I also had this problem and ultimately changed spark plugs really helped. Could also be your LPHP sensor.

[GEOS07335i]

Do you have any misfire issues? Or just rough idle. How many miles on your car and when was the last time you changed plugs and coils? Had similar issues. I swapped injectors, plugs coils ultimately it was my precat o2 sensors that went bad. There only good for 100k so it's a maintenance item for sure. You could also try cleaning your vanos solenoids quick 30 minute job and it's supposed to help with rough idle. I will admit it didnt help much in my case but it did quite down the "lifter tick".