PO301 code for my E 350 Coupe Question?
05-17-2018, 05:12 PM
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E350 Coupe
PO301 code for my E 350 Coupe Question?
I have bought this Merc on Oct 13 2017. Now I had a on again off again hesitation and subsequent engine code. Checked into it its a PO301 Cylinder 1 misfire detected. As recommended by the good folks at AutoZone I replaced Coil pack and spark plug in #1 Cylinder. Still has the sputter and engine light on. I called them and they said it could be a faulty coil pack or brand new Bosch double platinum plug. So I will go there and get a replacement and try again. Has anyone had this problem and fixed it themselves? A bit of a novice when it comes to fuel injection. Any help or feedback would be appreciated. Thanks in advance.
05-17-2018, 07:23 PM
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I've found AutoZone to be hit and miss on parts and they like to sell you all kinds of stuff on guesses. What spark plug is in it now? Bosch or NGK are oem plugs. Edit - I see you installed Bosch.
Need 3 things for proper fire : fuel, air, compression. Assuming you have compression, leaves fuel and spark. Swap the coil pack (and boot) with one from another cylinder. If the misfire happens on the other cylinder then the coil pack and/or boot is the culprit.
If misfire remains in the same cylinder unplug the fuel injector at that cylinder. If no change in running then either harness/connector or injector itself has a problem. If engine runs worse that's good actually, it tells you that the fuel supply is probably ok. I use a homemade led light as a noid light to check if the harness is providing current pulses to the injector. A quick check also is to put a screwdriver or hose on the injector while running and listen if it's constantly clicking. But that's not telling you if the injector is clogged. Generally injectors last a long time but you never know.
Try the simple tests first.
Need 3 things for proper fire : fuel, air, compression. Assuming you have compression, leaves fuel and spark. Swap the coil pack (and boot) with one from another cylinder. If the misfire happens on the other cylinder then the coil pack and/or boot is the culprit.
If misfire remains in the same cylinder unplug the fuel injector at that cylinder. If no change in running then either harness/connector or injector itself has a problem. If engine runs worse that's good actually, it tells you that the fuel supply is probably ok. I use a homemade led light as a noid light to check if the harness is providing current pulses to the injector. A quick check also is to put a screwdriver or hose on the injector while running and listen if it's constantly clicking. But that's not telling you if the injector is clogged. Generally injectors last a long time but you never know.
Try the simple tests first.
05-21-2018, 04:23 PM
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After driving it on a 45 min drive turned it off and miraculously the light is now out and it is not misfiring at all. i am going to change all the plugs and cross fingers. Thanks for the reply
05-21-2018, 06:04 PM
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Over a year ago my car had a misfire one cold morning. Shut it off and restarted it, no misfire. Happens sometimes.
Be sure all connectors and coil pack boots are secure and dielectric grease is used at plugs. Not that you will, but driving w flashing cel (misfire) will cause the ecu to move to a rich mixture. Not good for the catalytic converter or O2 sensors.
Be sure all connectors and coil pack boots are secure and dielectric grease is used at plugs. Not that you will, but driving w flashing cel (misfire) will cause the ecu to move to a rich mixture. Not good for the catalytic converter or O2 sensors.
