[slimjim760]

I need help figuring out where to start with my 2011 328i, which has 124k miles and recently showed a check engine light. The OBD scanner shows codes P0491, P0419, and P0420. I began by inspecting the secondary air pump and found that one of the hoses connected to the valve was barely attached and wouldn’t stay clipped. After replacing the hose, the car still runs poorly with slow acceleration, rough idle, and erratic shifting. It's an automatic, but it shifts late and sometimes jerks or struggles. I just bought this car a couple of months ago and have no idea where to start. Any advice would be helpful.

[tcphoto]

A smoke test will be a good step, it will reveal any unmetered air getting into the system.

[Gemini562]

You’ve got a few issues here, so let’s break it down. Start by checking for any more vacuum leaks, especially since that hose was already loose. The codes suggest air injection problems, and maybe even a bad O2 sensor. A good idea is to go over all the vacuum lines and maybe run a smoke test to find any sneaky leaks. Also, take a look at the O2 sensors, they might be throwing things off. If it’s still acting up, the catalytic converter or MAF sensor could be worth checking out next. Stick with the basics first, and you should start narrowing it down.