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Q: My 2002 Ford Expedition is running too lean with misfires.

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02 Ford Expedition 4.6L 173k miles with K&N air filter check engine light came on code bad egr valve I replaced that but trans would stick accelerating up shifting especially freeway speeds. Days later other codes came up too lean for conditions bank 1,2 and cylinder 4 I then changed spark plugs, pcv and pcv hose, battery and swapped out 2 coils cyclinder 3,4 and finding now it will not go faster than 30 mph. I changed the trans speed sensor but nothing changed. I have vacuum to the egr valve top of engine driver side completely dry while passenger side very wet oil and coolant leak from heater core especially in spark pug wells 3,4 cylinder. Everything ran fine before heater core was changed first it was venting allot into cabin then after venting allot in engine bay. An auto shop scanned it and looked at saying. The vehicle probably was submerged in water. The codes they was getting cylinder 2,3,4 coils bad and trans reading 9000 rpms sitting still.

My car has 17200 miles.
My car has an automatic transmission.

Hello. It sounds like you may have a few issues going on here. I usually start by checking the codes in the computer myself. This will give me a good idea of what my be going on and what cylinders are having issues. The most common problem to cause misfires on this engine is bad ignition coils. These are common failure. I will usually test them either by switching them to see if the misfire changes or test them with an ohm meter. I then remove the spark plugs and inspect them and do a compression test. This engine also has a history of bad valve seats which will cause all of these issues. All of these need to be checked first. At that point the intake manifold needs to be checked as I have seen a lot of these with cracked intake manifolds that will cause this. You should have this checked out by a certified mechanic, like one from YourMechanic, that can come to you to [diagnose why the engine is misfiring] https://www.yourmechanic.com/services/engine-is-misfiring-inspection

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