P0171 & P0174 | Ford Explorer Forums - Serious Explorations

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P0171 & P0174


Well-Known Member
February 17, 2006
Reaction score
City, State
Binghamton, NY
Year, Model & Trim Level
'99 Sport
Hey everyone, I know this topic has been covered many times as I already looked at search, but I just wanted to get a little bit more insight. Yesterday night I got these two codes (Bank 1 & 2 too lean). It has been cold lately, and my car will start just fine, but it will usually idle rather high right after startup, and often times the rpm's just decrease till it dies. Ususally when I put the car in drive, the car will idle. Also, when cold, the car feels like its heavily bogging at low RPM's. Once the car has been running for ~ a minute, it runs fine. Autozone told me i needed new O2 sensors, which I definitely dont believe. I know the problem has to do with too much air or too little fuel. The one thing is, if my car is dying when it should be idling, could it be a vacuum leak? It would seem like if it was leaking, it would want to surge at idle. I have an appointment at a shop next week to check it out, and even though I trust them, Id rather have the search more focused to save money. So, what do you think? Upper intake O-rings? Fuel Filter? Fuel pump? Anything else to check? Thanks a ton for your help, and once again I apologize for posting again about this often covered subject, but I wanted to see what you had to say about my specific symptoms.

Edit: I also have a MAC intake, and I guess another possibility is a dirty Mass Airflow Sensor/ or could the cold air have any effect?