Power Loss Mercury Mountaineer

1999 Mercury Mountaineer
I have a 1999 Mercury Mountaineer 5.0L V8. It just recently began acting up. After warming up the engine goes through heavy power loss and inability to climb ANY hill. Usually cannot get above 30-35. I just recently replaced plugs and wires for a tune up and a faulty coil pack (approximately 5-6 weeks ago) causing a misfire on cylinder #8. Today in troubleshooting I attempted the “Backyard Mechanic” trick of unplugging the MAF sensor and took it down the road, no change at all in acceleration issues or on idle, truck runs the same. Unable to spot any exhaust or vacuum leaks or issues, recently cleaned MAF housing and changed Air Filter as well. All of these issues arose after a heavy ice storm, do not know if this had any impact or was just bad timing. I need help, any ideas??


I see you stated you cleaned the MAF sensor. More damage is done trying to clean the MAF sensor than good. However unplugging the Sensor should have kicked the check engine light on and forced the closed loop mode and run fine. Since it did not do this the next thing I would check would be the fuel supply. Check fuel pressure, etc. Might try power braking against a building while someone sprays a shot of starting fluid in the air filter to see if the engine revs or bogs.  If it revs, the engine is starving for fuel. If it bogs, then you know it is not starving for fuel. Move to checking the exhaust back pressure at the O2 sensor ports. 1 1/2 psi is normal, anything 3 psi or more is a restriction.

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