Wouldn't stuck lifters cause a valve noise, which the car does not have? I'm thinking moisture might seep into somewhere over time, and because the car is not used, heat does not evaporate it. The camshaft position sensor is on the driver side front. There isn't one on the passenger side. There is a CRANKshaft position sensor near the firewall.

I am planning to erase the codes, check the caps, measure the resistance of the coil ignition wires, then place a timing light on each wire to see if the ignition is there at times of trouble. Also will try to measure the fuel pressure. I hope I have the correct fitting. Maybe I could tap into the Oxygen sensor circuits to see if there is a closed loop, and rich or lean condition. I hope for some new codes to show the way. Is this a good course of action?

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2004 E500 4Matic 138,000 miles