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P0171 Lean Code Vibe '06, Moving F/B at stop light during first 15 minutes of driving

Posted: Thu Nov 15, 2007 12:21 am
by CrucialKontact
I took my Vibe '06 in for service 5 days ago because the check engine light is on and steady. After about an hour they said the P0171 lean code is generic and may be an oxygen sensor. After another 30 minutes they said the sensor tested bad and replaced it for me.Well, here I am 5 days after with the light on again. (third time, first time I took it to a Valvoline Oil quick change and they decided to clear it. I didn't know it cleared the memory at that time)After they serviced it my vehicle will sort of shake during the first 15 minutes of driving whenever I stop, at a light for instance. The car literally moves forward and back, sometimes a little, sometimes I can see it move through the window. This was also happening the during the first occurance about two weeks ago when I brought it to Andy Moore's GMC service center for new tires, fuel system flush, brake fluid flush, and brake pad replacements.The engine light didn't come on for about 3 days after.Vibe has a litttle over 45,000 miles in under two years. I have also been putting premium fuel in it for about 2 months now 91-93 grade.I wanted to get some expert advice before I bring it back to the service center.Thanks up front

Re: P0171 Lean Code Vibe '06, Moving F/B at stop light during fi ... (CrucialKontact)

Posted: Thu Nov 15, 2007 12:46 am
by kevera
Does the P0171 show up now and is the light on?Did the dealer disconnect the battery when they replaced the 02 sensor?Did this just start happening after you got the injectors cleaned,because maybe some crud is stuck up in one of the injectors.Or will that throw another code.

Posted: Thu Nov 15, 2007 5:25 am
by CrucialKontact
Yes the light is on again. What on my vehicle could cause it to move back and forth so much in an idle position? After about 10 minutes or so of driving I don't feel it anymore. It only happens during the first 10-15 minutes each day. I plan on taking it back tomorrow or Saturday.I just wonder if they know what they're doing or not.

Posted: Thu Nov 15, 2007 6:59 am
by engineertwin2
Bad front O2 sensor can cause that cycling if you are getting the P0171.More than likely, its a MAF sensor issue. Try using some brake cleaner to clean the MAF sensor before you attempt to replace it. You may also have a vacuum leak downstream of the MAF causing this.Have you replaced the PCV valve lately? Check the hoses for that.Lastly, any did this happen after a fuel up? Might also potentially be low fuel pressure brought on by a dirty fuel filter...

Posted: Thu Nov 15, 2007 7:40 am
by engineertwin2
I mean, I'm basically assuming that the engine is surging (rpm going up and down) while it lurches forward and back...