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MB Paul
MB Paul, Mercedes Technician
Category: Mercedes
Satisfied Customers: 3567
Experience:  Qualified Mercedes Benz Diagnostic Technician - 20+ years experience - Workshop Foreman for Mercedes
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I have a 2000 Mercedes E320 with 179000 miles. Just recently

Customer Question

Hi there! I have a 2000 Mercedes E320 with 179000 miles. Just recently had the plugs and wires changed and also the conductor plate on the trans. On a couple of occasions now when I'll be driving on city streets the check engine light would start flashing then stay on and my car would start loosing power like it was running on 3 cylinders. I would just pull over and stop, turn the ignition off, pull out the key then push in the key and start the car and drive off as if nothing happened. The check engine light would still be on and I get home and put my scanner on it and it would read error codes P0300,P0304,P0305, P0306 and P0150. I would clear the codes and the car would drive as if nothing happened. I've driven for many more miles until it happened again. And I would clear it the same way. I thought it my be my coil paks but the mechanic that did the tune up said if it was that the car would run rough all the time. Any suggestions????
JA: Does the light stay on, or does it blink?
Customer: The light would first start blinking then it would stay on immediately after that until I clear the codes.
JA: Are you fixing your E320 yourself? What have you tried so far?
Customer: No I have a mechanic that does all my repairs on this car. He's changed the plugs, wires, air conditioning compressor, conductor plate on the trans that was done 2 weeks ago.
JA: Anything else you want the mechanic to know before I connect you?
Customer: No I can't think of anything else right now.
Submitted: 2 months ago.
Category: Mercedes
Expert:  Jeromy Madison replied 2 months ago.

Those codes are a hard misfire caused by either ignition or fuel. Could be fuel injectors as well. It is likely that when the computer sees these faults it shuts off the fuel injectors and then when you restart them they turn back on.

Customer: replied 2 months ago.
But I don't understand. If the car misfires, wouldn't it keep misfiring if it was ignition or fuel injectors. Could it be electrical where there's a drop somewhere in the harness maybe? Why would the car run normal after I restart it for a long period of time?
Expert:  Jeromy Madison replied 2 months ago.

You are right, for some reason the car is misfiring and apparently turning off the fuel injectors. This is one issue that will be very difficult to solve without having the vehicle in my hands connected to a scan tool. Has the mechanic read the long term fuel trim and short term fuel trim to see what it is doing as it is running?

Customer: replied 2 months ago.
No he hasn't but I'll mention that to him. It's very puzzling because I drove it over 200 miles in one day and it ran flawless in the 109 degree heat. And this just happened again just driving 4 blocks away from my house ready to go on the freeway.
Expert:  Jeromy Madison replied 2 months ago.

It is very possible that the issue could be either in a faulty ground or in the ecm itself. All of the ignition system has been replaced?

Customer: replied 2 months ago.
but not the ignition paks. Again, if it was one of the ignition paks it would run rough all the time. If it is something electrical how would you find problem? Is there a way to test what's going on with the ECM? How would you find a faulty ground and where would you start since it only happens when the car is running.
Expert:  Jeromy Madison replied 2 months ago.

Not true. The coil packs can be very tempermental. They will work and then not work. Usually they will work when cold better than warm. But looking at the codes, you have misfires all on the same side, so it is isolated to something on the right side. Could be an air leak or a catalytic converter that is partially clogged.