I have a 2006 Ford Taurus with the 3.0L Vulcan V6. It’s got just over 130k miles and the idle has a little jump while sitting or stopped in traffic. The idle jumps between 650-750 rpms. Check engine light came on one day, had it checked and said cylinder 3 misfire. Noticed the headlights dim in and out a bit while it’s idling too.
I’ve replaced the spark plugs and cleaned the IAC and it didn’t smooth it out. Any insight on this?
why you have to figure out why number three is misfiring offense the simple as a bad spark plug or bad ignition coil on number three
try that first because fuel injectors can do that but they cost more and are much harder to put on and of course if it has internal engine wear like a blowing head gasket bad piston ring bad velvet number three then it gets super expensive to rebuild the engine
The code says Cylinder 3 misfire. This isn't an air/fuel issue at idle from a faulty IAC valve. So it's either an injector or an ignition problem on the #3 cylinder.
It's probably not an injector.
Also when your RPMs drop from the misfire your alternator isn't spinning fast enough so it's probably why your headlights dim.
The Ford coil pack is the most likely suspect although an arcing spark plug wire could also be the issue.
If you just want to chuck a few parts at it with a decent probability of fixing the problem then, coil pack and spark plug wires.
But, there's a couple of "low tech" ways to check ignition issues on a single cylinder.
To check for an intermittent arcing plug wire, grab a spray bottle of water, wait until dusk and then spray that #3 plug wire, from the coil tower all the way to the spark plug.
The low light at dusk will make it east to see any arcing through the plug wire insulation to a ground.
Do it at a variety or RPMs.
As far as testing the coil pack. Get one of those test lights from the auto parts store. (less than $10 bucks) Not one with an LED light, one with a light bulb.
As a "baseline" pull the #1 plug wire off of the coil pack (No misfire codes there) and with the test light's alligator clip on a good ground, put the probe into the #1 coil tower (without touching the edges of the coil socket) and slowly pull the test light's probe up.
As you pull the test light above the coil tower you'll see the spark arcing above the coil tower to the test light's probe.
Next do #3. (Misfire Code). Same setup. If when you pull the test light's probe above the #3 coil tower the spark doesn't jump to the test light's probe, like it did at the #1 coil tower, but instead jumps inside the coil socket then you have a short in the secondary winding within the coil.
Replace the coil
