[Cm452]

I've got a mixed bag of injectors: 6,8,9 indexes, ~2 of each. I know the 9s are of I'll reputation, but, the car runs well otherwise. Consensus seems to be a perfunctory change up to index 12s, but I'm curious as to the actual risks of popping my motor with a tune and older injectors ?
If one of my injectors fails by leaking, I can handle that. If it fails at WOT by going super lean, that I cannot.
I guess what I'm asking is how common it is for injectors of those indexes to fail catastrophically?
I've used the search function, but there are a lot of parrot posts without any explanation aside from "just do it".
Thanks!
-Cm

[N54Society]

There is no inherent risk of popping the motor with older ones. I would change them as needed. Injectors fail at random. Even index 12 injectors have failed before. Ideally, you run the latest because it has the least "shelf life" and they MAY have some kind of design change to improve the internals (just a solenoid really).

Only thing you need to consider is that if you swap in an index 12 in bank 1 (cylinders 1-3), the remaining injectors in that bank need to be 11 or 12 as well. Same goes with bank 2. Are the injectors you described new?

[Cm452]

Thank you for your thorough reply! I have no idea how old they are in years or in miles. I bought 'er at 90k, up to 97k now. Lots of dealer maintenance records, but they just say "fuel system service" on the carfax.
It does, every once in a while hiccup when it's cold. Carbon cleaning was apparently done recently.
-Cm

[Jonah335]

These injectors won't fail catastrophically. You will be able to see the symptoms well before it gets to a point of actual danger to your engine. mine would spit gas out of the exhaust on cold starts and ended up staining my driveway. as well as running rich and fuel smell, you will be able to see the symptoms I'm sure.

I would say put the 12's on the back burner unless you have the budget or love proactive maintenance.

[Chris@VargasTurboTech]

Nah, just be ready to replace them if/when you see they're misbehaving. As long as logs look good, car starts/idles/decels fine without any signs of leaking (a/f doesn't immediately go to max on decel), I'd keep running them for a while.

[rediahad]

I was getting superknock in 3 cylinders. I hear thT is really bad so i swapped injectors out for 12s and im good now

[RnmEvo9]

Originally Posted by Jonah335

These injectors won't fail catastrophically. You will be able to see the symptoms well before it gets to a point of actual danger to your engine. mine would spit gas out of the exhaust on cold starts and ended up staining my driveway. as well as running rich and fuel smell, you will be able to see the symptoms I'm sure.

I would say put the 12's on the back burner unless you have the budget or love proactive maintenance.

I can smell fuel out of my brothers 335i everytime he shuts off his car, where would be the best place to order index 12 injectors just in case?

[autoart]

I thought if they start leaking fuel down into the oil, it can cause premature bearing wear.

[N54Society]

Originally Posted by RnmEvo9

I can smell fuel out of my brothers 335i everytime he shuts off his car, where would be the best place to order index 12 injectors just in case?

Could be a number of things but a likely one is this:

https://www.e90post.com/forums/showthread.php?t=1417068

[hellokitty]

Originally Posted by RnmEvo9

I can smell fuel out of my brothers 335i everytime he shuts off his car, where would be the best place to order index 12 injectors just in case?

Fcpeuro due to their lifetime warranty.

With that said, I’m tuned and running on index 9s and so far so good. Will update to index 12 once they start misbehaving.

I’d also check whether you fall under the Bmw extended warranty for fuel injectors so you don’t have to pay out of pocket.

See SIB 010215

[rediahad]

Search classifieds. I saw two guys this week selling new index 12s

[Jeef]

Originally Posted by autoart

I thought if they start leaking fuel down into the oil, it can cause premature bearing wear.

I've seen a motor go because of this.

[Silent9n54]

im running index 1s at 21.5 psi for over a year with no issues

120.000+ miles