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Old 09-10-2017, 11:07 AM
tomw0 tomw0 is offline
Ford Ranger Driver
 
Join Date: Aug 2015
Posts: 1,086
Default Re: Rough Idle, P0171, Tried Everything

"Lean" can be lean from lack of fuel or excess O2, or can be lean interpreted by O2 in the exhaust because of misfire. Misfire leaves the O2:fuel mix intact, so there are O2's floating by the sensor.
A 'pop' can lead to hoses popping off their 'spot' or splitting, thus leaking extra air into the engine that is not measured by the MAF, if you have a MAF. Extra air can cause misfire.
I'd check the vacuum in the intake with the engine running at idle, and also take a look at all vacuum hoses, and even the EGR diaphragm if you have one.
The Lima first had a 'backfire' valve on the PCV line that was spring loaded, and could/would pop out of place on occasion. That made the idle terrible. Once figured out, I knew what was wrong when it happened. I don't think they use that any more.
I'd suggest checking for leaks. If the temp sensor is cooked, they don't cost a lot to replace. It should be screwed into the intake manifold, and easily accessible.
tom
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