Melted Coils (FIXED)

2005 Nissan Sentra 1.8 lts. was brought to my shop because it keeps melting the coils (it has 3 duralast coils and 1 OEM used coil). I took a coil ramp capture and it seems ok amperage wise,but I am unsure of the dwell time.

As I watched some live data the STF is around 0 to +2, and LTF is at 0. The only thing that stands out is the Ignition timing advance which is around 18 degrees at idle, when I raise the rpm the other thing that stands out is the fact that the STF goes really negative (-17), I'm suspecting a skewed MAF sensor tricking the computer in to subtracting fuel needlessly, making the coils working harder, but that's only a guess.

Car has no fault codes.

Thank you for your time.

You know, I've heard of this before, though never ran into it personally. These are supposed to have ground problems where the cable attaches to the transmission, evidenced by arcing on the cable eyelet.

It may be intermittent, which might explain the good coil current draw you're seeing on the scope. Maybe try voltage drop checking the coil ground during cranking?

How about you look at your secondary while loading the Engine and look at a Injector voltage waveform. Then monitor your fuel pressure also while it's loaded. If your secondary burn line goes up at the end this proves it is running lean and then also monitor your fuel pressure while this happens. Then look at the Injector on time and see if the on time is smaller when the fuel trim is going negative. This would prove your theory. However you still need to figure out why the vehicle is taking away fuel. What type of Mass Airflow sensor is this?

Tyler wrote: You know, I've heard of this before, though never ran into it personally. These are supposed to have ground problems where the cable attaches to the transmission, evidenced by arcing on the cable eyelet.

It may be intermittent, which might explain the good coil current draw you're seeing on the scope. Maybe try voltage drop checking the coil ground during cranking?

Here's powers and grounds for the coils.

busjockey1.. wrote: How about you look at your secondary while loading the Engine and look at a Injector voltage waveform. Then monitor your fuel pressure also while it's loaded. If your secondary burn line goes up at the end this proves it is running lean and then also monitor your fuel pressure while this happens. Then look at the Injector on time and see if the on time is smaller when the fuel trim is going negative. This would prove your theory. However you still need to figure out why the vehicle is taking away fuel. What type of Mass Airflow sensor is this?

The car is obviously gone, and I did do a secondary waveform like you said, but I can't find the file (you know how it is when you get work in), but here's an injector file of it while at idle, 2500 rpm and WOT, just for learning purposes (me being who learns obviously ).

Here's a zoomed in view of power's and ground's

Please tell me what you think

So what did you do to fix it? Did you recheck the secondary loaded to make sure you still didn't have a problem? What type of Maf is on this vehicle?

busjockey1.. wrote: So what did you do to fix it?

Well it turn's out I didn't get the full story and the customer first had a severe misfire going on "for a while", so when they did change the coils, the cat was impregnated with fuel, so the computer was leaning out the engine because it saw it was "rich".
So in conclusion, I didn't really "fix" the car it was only a matter of time for the cat to be "clean", and the trims got back to normal at hi rpm's and at idle.
At least I got to play with my pico, save some waveforms, and learn some stuff on the way.


About the secondary captures, I'm not really ANY good so I rarely use them, any material you'd suggest other than experiment with good running cars?