DIS misfire isn't plug or wires. What now?


#1

I have a 2004 Dorf Freestar, 130k miles, with a rotorless “DIS” distributor/coil system. It started experiencing a rough idle and reduced power. I put an OBDII scanner on it, and it read “misfire cylinder one”. So far so good; I figured it was maintenance, and replaced all the sparkplugs and plug wires. The old sparkplugs looked fine, and the symptoms persist. Any experience as to what I should try next?


#2

Anytime an engine performance problem exists a compression test should be performed; especially on vehicles up in the high 5-digit mark or more in mileage.
While a 130k miles motor normally should not have any mechanical faults it’s always a possibility. You weed that out right off the bat.

After that you might consider the possibility of a failing coil or injector fault.
With the engine running you might listen to the injector with a mechanic’s stethoscope or long handled screwdriver serving as one and determine if you hear the injector clicking or not.
If you hear the injector clicking then a look at the coil pack might be in order. Hope that helps.


#3

It could very well be that the coil pack has failed for cylinder #1.

Tester


#4

You might try reversing the #1 wire with the adjacent wire on the coil, #5 I bellieve, to see if the miss changes to that cylinder.