Code PO171 - System too lean (bank one)
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Joined: Feb 2002
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From: Riegelsville USA
Code PO171 - System too lean (bank one)
Been having an ongoing problem with my truck and have replaced many emission parts trying to get her to run right ..... I have a 95 Ranger STX 4x4 super cab with a 4.0 L . Truck occasionally idles rough and surges or " trailers " when engine is HOT . Been trying to get a code to come up ..... Finally the check engine light came on and I pulled a code : PO171 . The manual calls this a System Too Lean ( Bank 1 ) . Can anyone please tell me where to begin now ? My Haynes manual has nothing I can find on this subject ........... Thanks ..... RICK in Penna. 
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From: Warren, MI
Code PO171 - System too lean (bank one)
[updated:LAST EDITED ON 13-Mar-02 AT 11:28 AM (EST)]Rather than explain my problem, scroll down on page two for (Attn wptski). What parts have you replaced?
I'm going to buy/order a IAC valve after work today. My problems got much worse after cleaning it. It's getting full voltage with KOEO and doesn't move. I put the voltage right from the battery to it, it makes a snap put valve is still wide open. Resistance checks okay.
I'm going to buy/order a IAC valve after work today. My problems got much worse after cleaning it. It's getting full voltage with KOEO and doesn't move. I put the voltage right from the battery to it, it makes a snap put valve is still wide open. Resistance checks okay.
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Joined: Feb 2002
Posts: 1,534
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From: Warren, MI
Code PO171 - System too lean (bank one)
Hmmm, I'd like to know just how the IAC works? Not what it does, I know that! I mean what's inside it. Even with my Ford discount at $118(Ouch!), it works no different than the old one! It must be more than just a plain old solenoid. I heard that it was a stepping motor but think that's on the GM units.
I did pull the battery connection to reset the PCM and it could take a bit of driving to relearn. I did the same thing after cleaning the IAC, throttle body and MAF for the third time. A short drive popped the codes again! It idles even faster than it did before the cleaning. I figured between the three things I cleaned, the IAC would be the one that I screwed up.
I did pull the battery connection to reset the PCM and it could take a bit of driving to relearn. I did the same thing after cleaning the IAC, throttle body and MAF for the third time. A short drive popped the codes again! It idles even faster than it did before the cleaning. I figured between the three things I cleaned, the IAC would be the one that I screwed up.
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