1-Here's the deal. My 99 ML 320 will start to miss very bad sometimes when first started. Never when already running. At first i thought there was water in the line as it seemed it was not getting enough fuel. I added a bottle of gas line water remover and it worked fine. However at random it will still do it. When i have the problem, it will start fine but under load (in gear) i can not accelerate over 30mph and missed badly. If i stop, turn off key, and restart, sometimes it clears up and i'm on my way. Sometimes i add a bottle of water remover, restart and i'm on my way. Not sure if there is acxtually something in the fuel or just actually resetting by turning off key.
I have done the fuel pump upgrade. Is there an easy drain for tank? The last code reading i got was "fuel rail" and CEL is on.

2-i dropped my key and now will not work. checked batterys and have tried reprogramming per instructions found here on the forum. Also, when opening by key, alarm sould sound until you get the key in the ignition. Now alarm does not sound when i unlock door and can only open 1 door, not all four with key. i have to get in and unlock by button inside. Any suggestions?

Thanks for the help.

I believe when you unlock with key, you can only unlock the door you want to enter, the alarm will sound only if the truck was armed previously, i.e. using the remote. If you did you arm the vehicle using the remote, the truck was never armed. Using the key to lock the doors does not automatically arm your ML, that's why you don't hear the alarm go off. This is not the greatest design for the early year MLs. Unlike the bimmers, you can arm the car using the remote or using the key to lock the car.

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98 ML320 (gone but not forgotten)

I had the same problem with identical symptoms. When the truck started to miss check engine light will come on. I hooked up the code reader and it gave cylinder 1 missing. I changed the spark plug but it did not fix the problem. Then I swap the ignition wire with cylinder 2 and the problem followed the lead to cylinder 2.

Yesterday I bought the wire set and changed all the 12 wires and drove it under load with hard acceleration and nothing happen.

You can try changing the ignition wires, see if that'll resolve the issue.