I have a 2002 Ford Windstar 3.8L with engine codes P0171 and P0174, Can I replace it myself?
P0171 Fuel trim lean Bank 1
P0174 Fuel trim lean Bank 2
Yes, you can, this is more of an inspection rather than replacing a component, what usually causes the lean condition is vacuum leaks, look and listen for any vacuum leaks. Another cause for a lean code condition would be from the MAF (mass air flow) due to the new law. All manufacturers who produce air filters must apply a fire retardant this would prevent engine fire in case of an engine backfire through the intake to the air filter. In return the retardant tends to mask the MAF from measuring the air entering the intake. and as a result, measure the air as a lean condition. Fuel pressure is another But being a V6 engine this becomes rare. incapable of setting the system lean.
This vacuum hose that goes to the intake plenum caused a lean condition for both Banks,
The fix was to reconnect the vacuum hose, the cause, the owner washed the engine knocking out a few vacuum hose connections.
If you do, decide to clean the MAF. Ford recommends the use of brake cleaner.
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