System too lean?
 

Hi everyone, im new here and have been doing some research, but havn't found exactly what i am looking for. My MPV started running rough only while at idle. I immediately suspected something with the air flow such as cracked or broken hose, but after hooking up OBD II codes I got P0174, P0131, P0151, and P0171. Basically Too lean in banks 1 and 2. Did i really have 2 O2 sensors go bad at the same time, Or should I start elsewhere? I have inspected the PCV hose, and surrounding hoses but found nothing. thanks in advance.

Lean on both banks sounds like an MAF problem or a large vacuum leak. Clean the MAF and spray a flammable brake cleaner etc around the intake at idle. If the idle changes you found a leak. Pinch off the brake booster hose to eliminate that possibility.

What types of cleaners are acceptable for cleaning the MAF? I am currently stationed overseas, and i cant just go to a local auto parts store for some MAF cleaner. I have heard that rubbing alcohol might be ok?

i also notice that the rough idle is barely noticeable when the car is cold. It gets rough and surges once warmed up, and the issue only exists while at idle.

Alcohol and a cuetip should be fine for the MAF. Wet a rag with it to clean the throttle body. It probably idles higher when cold masking the problem. It could be a lot of things though. It's kinda hard to say without the van in front of me.

BTW thanks for your service.

thanks for your assistance and your support!

I have checked all the hoses and cleaned the MAF and throttle body with no results. It has now been in the shop for 2 weeks, and transfered to three different mazda dealerships who have not been able to find or correct the problem. are there certain parts i need to just order and start swapping?

check vac leaks in brake booster especially if it occurs with your foot on it. Mine had an internal leak. It has a large vac hose going to it from engine. Need to clamp off this hose and check idle.

so if there is an internal leak in the brake booster, is it repairable, or just need to replace it?

Replace. I got one from junkyard, not cheap new.
Now when i come to a stop, i put the gear in neutral and take my foot off brake and use hand brake, so hopefully it lasts longer.