Question about 2000 Ford Expedition
Hi, no, don't do that. The code 174 indicates a vacuum leak--not a bad sensor. The leak can be anywhere downstream of the mass airflow sensor on the inlet pipe. Sometimes the rubber pipe itself tears/cracks, or maybe there is a loose vacuum hose or a torn brake booster diaphram. Check all the hoses attached to the engine intake manifold for a leak at either end or in between.
If all hoses are good, next check the intake manifold askets for leaks. Get yourself a can of carb cleaner and start the engine. Spray the gaskets all around. If the engine speed changes, you have a gasket leak--replace the gaskets. Since you have a code 174 and NOT a code 171, this is the most likely cause of the problem, because only the rigt bank is running lean. Be sure to check the gaskets on that passenger side carefully.
Last of all, if all that was good, check to see if your EGR valve is stuck open. I have pasted instructions for removing the valve below (from autozone.com). Please let me know if you have questions and thanks for using FixYa.
EGR valve R&R.
Posted on Jan 03, 2011
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Posted on Jan 02, 2017
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