P0172 - Fuel Bank 1 Rich


New Member
Jan 22, 2020
M235i - RWD Auto, FBO, BM3
I picked up my 235 in October and promptly started to order parts and planning my build which I think had led to my first hiccup. I know a downpipe, tune and drop in filter seem to be the dominate advice but I wanted to prepare for a big boost or similar kit down the road. I haven’t gotten too far but am getting a CEL and a P0172 code.

So far I’ve installed: Evolution Racewerks CP, FMIC, turbo to intercooler pipe and a MST cold air intake. Got the code a few days after install, I noticed the vacuum line from the intake to that T and then the CP had crack in the connector where it connects to the intake side so I replaced it and it started drove for 40 miles with no codes. I put it in park and let it idle for maybe 10 min and it popped the code again. Exhaust smells of gas and is sooty.

I want to resolve this before I install the DP and put the tune on. I’m thinking of putting the OE intake back on to see if it clears the code but wondering if y’all have any other advice. I haven’t yet cleaned the MAF so I might try that first.

Also since it’s been rich I plan to replace the plugs...what is recommended for a FBO + Stg 2 BM3 tune? In Texas so have 93 octane if it matters.