[sw1183]

2008' 335xi 70k miles, JB4 – Map5 : First time post-er - long time viewer!

I have been getting the 29F4 code off and on since winter and I have also been getting slight hiccups when I am cruising along at 70mph with cruise control on. I have never been able to pinpoint the problem but now I am having rough starts as well. The RPMs will bounce around for the first 30 seconds and then typically is fine after that.

I did carbon cleaning last summer and replaced all spark plugs at that time.

I have read so many threads on this triggered code but don’t have any clear cut answers still. I am leaning towards O2 sensors but don’t want to drop $400 for 2 of them if this will not solve the problem. The code is typically triggered after I get off WOT.

Anyone have sound advice to check the O2 sensors or another trouble shooting method?

Thank you in Advance!

[hkninja]

Turn on autoclear for CEL. Menu 1/3

See if it will still give u the same issue.

[sw1183]

I'm happy to give that a try on the way home from work tonight. Are you saying that this will fix the rough idle also on startup though?

[sickem]

so you have catless downpipes on the car? The code in question is just a catalytic inefficiency code commonly thrown for folks who don't have catalytic converters. Usually oxygen sensors going throws lambda sensor codes. I think your hiccups might be unrelated to this code. Any other codes present?

EDIT: if you're lucky enough to be under a CPO warranty, I would just turn the clear function off as mentioned above and when the codes come back take the JB4 out and go into the dealer.

[sw1183]

Thanks for your Reply Sickem.

I have stock downpipes – Only Mod is JB4, Oil Catch Can and BMS Dual CAI. I would commonly have the intake Vanos code, but an oil change and cleaning that Vanos fixed that issue. I am not under a CPO warranty.

[sickem]

Originally Posted by sw1183

Thanks for your Reply Sickem.

I have stock downpipes – Only Mod is JB4, Oil Catch Can and BMS Dual CAI. I would commonly have the intake Vanos code, but an oil change and cleaning that Vanos fixed that issue. I am not under a CPO warranty.

Yeah could be the oxygen sensors. When banks 1 and 2 were accidentally switched by the shop that installed my catless DPs this symptom occurred. Fwiw, I replaced my O2 sensors around 57k mi and the shop said they were pretty nasty...might be time to do it.

[sickem]

If you do have to replace, I bought mine here...very good price:

http://www.oembimmerparts.com/category_s/1949.htm