Question about 1999 Ford Windstar
PO171 and PO174 "System adaptive fuel too lean (Bank 1)" and "System adaptive fuel too lean (Bank II)" The first time this happend I was told by the Ford dealership that I had an upper intake vaccum leak and that I had to replace the upper intake gasket and the 6 port seals. I did this and my problems went away for about 8 months. Now I'm getting the same codes with the new gaskets. The shop said it could be a Mass Airflow Sensor, but those are expensive if it's not the problem. I've replaced the PCV valve and the fuel filter in the past year. I did new plugs 2 yrs ago and I've installed a K&N air filter. Could my problem just be a leaky hose or something? What would cause both banks to lean out? It has started Idling a little funny at times and it surged the other day. Do I need to dig back into the Intake or is it an MAF sensor? Please help with any tips for diagnosing this problem that you can. Thanks.
If they did not replace the front valve cover with a new updated one when they did the intake the code will come back.there is a tech service bulletin about this . your mass air flow sensor can be cleaned but would recommend a shop do this.
Posted on Feb 01, 2009
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