Have a '99 F-150XLT 4.6L with 105,000mi. Had Service Engine light come on. Had the code read at AutoZone and it came up 171 - "Bank 1 lean". They suggested adding Lucas injector cleaner which I did but have not had it in long enough to really tell any difference. I changed the plugs a month ago to Autolite Platinum and it ran fine.
Any other suggestions for this error code?

 

For a code like this you need a scan tool to read the "freeze frame data". It will tell you wether the engine was warm or cold. At cruise speed or on acceleration, or at idle when the code was set. It will also tell you if the other bank of the engine was also lean but din't trip a code. It ican be hard to diagnose if you don't know when the problem occured. A couple things that you can check....is the PCV valve in place in the valve cover properly; if you had it out when tuning it up and forgot to put it back in, this will cause a lean code. Also check all vacuum lines for any signs of leaking.