Distributor Cap
Taking a look at my old distributor cap, the contacts were worn. Instead of them facing flat to the rotor, they had worn away and become angled. This is a good sign that I was correct to replace the distributor cap. I normally would replace the distributor rotor at the same time, but I'm still waiting for it to arrive. Summit Racing's website has good prices and 1 product I've ordered there came quickly out of a few, but other parts were projected to not arrive for over a month, so I bought it at
AutopartsWarehouse. Cost more, but I couldn't wait when I could hear my engine missing.
Spark plug wires.
Normally, on a vehicle of this age, spark plug wires probably should have been replaced a few times, but the stock spark plug wires have endured incredibly well. Checking the ohms of resistance, they're still better quality than spark plug wires available new on the shelf (at aftermarket parts stores).
I have put new platinum spark plugs, as per recommended by Nissan in the 2004 owners manual. I've run them through about a year of driving and while they have needed some regapping to be running just right, they still don't look worn...good for the spark plug and the condition of my engine, bad as I don't want to waste them and I've been dying to try out some iridium spark plugs for months, lol (They're on my shelf just waiting for me! They were on sale, that almost never happens.).
Timing Advance.
Timing advance has a modern technique to it in current designs. Cars adjust their timing advance continually based on load and RPM. Generally the faster the engine is spinning, the more timing advance you need. Meaning, the spark will be initiated before top dead center or BTDC. The flame front takes time to fully combust the fuel, so at higher RPM more timing advance was needed.I observed through my torque app that timing advance went up to 28 degrees when I let off the gas completely or went into neutral. It'd come down to 10 to 16 degrees of timing advance when under load or acceleration.
I believe the truck was compensating for the worn distributor cap. Now it behaves normally when accelerating by going up instead of being decreased. I believe the additional gap from the worn points in the distributor gap was making the flame front be late due to raised resistance. So the PCM has a program to compensate.
Truck Miles per gallon.
Now that this has changed, my truck's miles per gallon when cruising seems to be a lot better. I won't report back until I've used a couple gas tanks of gasoline to be sure versus just the belief of improved miles per gallon that has been estimated by my Torque App.
by AutoBravado
