Misfire? Bad Coil? Diagnosis Please!
#1
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Hello, I'm new here so I hope this is the correct place for this.
I'm running a 2008 Twin Turbo LY2 4.8L using megasquirt I for fuel and an MSD box for spark.
Checked my plugs, they all look the same and clean.
The car does drive but it seems like it's slightly misfiring, completely noticable when you try and hold an rpm in neutral.
Load does not seem to make it worse, I drove the car two days before realizing how bad it was and stopped.
I haven't gone into boost yet so I doubt I've damaged the engine mechanically yet.
Video of me holding the throttle perfectly still.
Datalog
---------
As you can see it's showing lean AF along with the rpm dips.
Which could also be because it's not sparking and O2 sensor is reading air.
![](http://img546.imageshack.us/img546/3939/megagraph.jpg)
I'd rather not start replacing stuff just as a guess.
But my best guess would be ignition related partially due to the symptoms and also the megasquirt setup hasn't changed.
Let me know what you think. This is my first non-distributor motor. Even any generic tips on testing coils or anything would be helpful.
Thanks to everyone who takes the time to reply.
I'm running a 2008 Twin Turbo LY2 4.8L using megasquirt I for fuel and an MSD box for spark.
Checked my plugs, they all look the same and clean.
The car does drive but it seems like it's slightly misfiring, completely noticable when you try and hold an rpm in neutral.
Load does not seem to make it worse, I drove the car two days before realizing how bad it was and stopped.
I haven't gone into boost yet so I doubt I've damaged the engine mechanically yet.
Video of me holding the throttle perfectly still.
Datalog
---------
As you can see it's showing lean AF along with the rpm dips.
Which could also be because it's not sparking and O2 sensor is reading air.
![](http://img546.imageshack.us/img546/3939/megagraph.jpg)
I'd rather not start replacing stuff just as a guess.
But my best guess would be ignition related partially due to the symptoms and also the megasquirt setup hasn't changed.
Let me know what you think. This is my first non-distributor motor. Even any generic tips on testing coils or anything would be helpful.
Thanks to everyone who takes the time to reply.