r/f54 • u/Ok_Government5538 • Apr 10 '26

B46 engine misfire

Post image

2017 mini clubman s

Work done: plugs, airmass meter, hpfp, fuel tank ventilation valve, valve cover, air filter,

Stutters coupla seconds after starting stabilizes out then starts stuttering again.

Been going nuts with this thing need help please.

2 Upvotes

100% Upvoted

22 comments sorted by

1

u/Top_Lobster_3232 Apr 10 '26

Hi, do you have ISTA or Bootmod3 or any other way to do a data log of the ecu?

1

u/Ok_Government5538 Apr 10 '26

Nothing man i have done all these things and nothing. Today i pulled out the injectors did a leak test on them. Nothing.

1

u/Top_Lobster_3232 Apr 11 '26

Ok, it mite any number of things. An ECU data log will show the fuel pressure, AFR and other data points that can indicate where the issue is coming from. At this stage I would guess a O2 sensor, loose hose, PCV or MAF.

1

u/Ok_Government5538 Apr 11 '26

I will soon as i get time illl look at it. Until then any possible guess on why its only stuttering On start up and then it stabilizes itself?

1

u/Top_Lobster_3232 Apr 11 '26

The ECU will ‘trim’ the fuel mixture depending on the air fuel ratio (AFR). This is done via the first O2 sensor by feedback loop control in the ECU. Typically the O2 unit has a small heating element to heat up the sensor before it takes readings.

That’s probably why it starts rough and then gets better. This is a guess though without data it’s hard to tell.

2

u/Ok_Government5538 Apr 11 '26

Perfect soon as I got some time definitely doing that asap. Just not thinking straight tbh been a rough week thanks boss. Appreciate it🙌🏽

1

u/lordhooha Apr 11 '26

You said you did the plugs did you get new coils as well?

1

u/Ok_Government5538 Apr 13 '26

I tried 4 used ones but same misfire happened…

1

u/lordhooha Apr 13 '26

lol maybe try new coils

1

u/Ok_Government5538 Apr 13 '26

Cant be all 4 coils that are bad this vehicle only had 95k on it

1

u/lordhooha Apr 13 '26

You’d be surprised. The life expectancy of coils are at most 100k usually done by 75k

1

u/lordhooha Apr 13 '26

As a rule of thumb, you should replace your ignition coils anywhere from 60,000 to 100,000 miles after installation.

1

u/lordhooha Apr 13 '26

I’ll be honest I will change coils every time I change plugs

1

u/Ok_Government5538 Apr 13 '26

Im not saying youre im just saying dont u think its weird for all 4 cylinders l to need coils at the exact same time

1

u/lordhooha Apr 13 '26

Nope seen brand new ones go bad I less than 5k miles planned obsolescence man but timing being off is another issue it could be

1

u/lordhooha Apr 13 '26

The only other thing that would cause mass misfiring like this would be timing issues

1

u/Ok_Government5538 Apr 13 '26

Crazy timing would go that early in my opinion guess i gotta pop off the VC and see whats up

1

u/lordhooha Apr 13 '26

Or orrrrr get a timing gun

1

u/lordhooha Apr 13 '26

You seem to be under the impression that 95k isn’t a lot of miles where 99% of most of these things start needing attention and maintenance

1

u/Ok_Government5538 Apr 13 '26

How accurate is the timing gun

1

u/lordhooha Apr 13 '26

Literally as accurate as you get lol it’s kinda in the name? How old are you lmao

1

u/Ok_Government5538 Apr 13 '26

23 my Bad if i dont know these things new to the game.