Today I was doing a lot of city driving so I decided to check my mode 6 every couple miles and at every stop. Virtually no misfires today but the rough idle was still there. I'm not sure what this means but maybe someone out there does. Oh and I also tested the resistance of the multimeter shorted together and it was .3 ohms which would put the primary resistance of the coils closer to .55 ohms, so those may be to spec.

 

As for your misfire issue, again I say, Specific ohm readings on COPS are not particularly meaningful - outside of ZERO ohms (open-circuit). And if one has an open primary or secondary you're going to have a dead miss. As @StephenG suggested in post #11 (this thread), they very rarely fail - other than deteriorating boots and/or corroded tips or springs. And for my part I believe, if not removed, the accumulation of carbon in the spark plug holes that causes plug breakage is a significant cause of continued random misfire problems.


As for the rough idle issue - I do not think it is spark related. I believe it is fuel or compression related. Fuel being unbalanced injector delivery. For that, if SeaFoam or several injector treatments through the gas doesn't help, I could only suggest remove injectors and try to clean them THOUROUGHLY or replace all of them. Compression is another matter - but easier to check, and a good prfessional compression test can be invaluable in making good decisions about more extensive repairs down the road, if needed. If it were me, in the same situation - I would remove all injectors and soak them / clean them vigorously by forcing strong solvents through them - forward/backwards - while electrically actuating them, and replace all o-rings on reinstall. If that didn't do it - proceed to the professional compression test, before deciding to replace all injectors.

 

Rough idle could be a symptom of a timing issue. Could be in the early stages.

 

Comparison readings are the rule ,one versus others . It just gives you an idea of a bad failure of the coil . The job of the coil is to produce high voltage each and everytime. Ohms is not going to tell you that it is breaking down, it may tell you you have an open winding . Coils are very high voltage, a short between windings can kill the high voltage and you will never see that on an ohm meter.
The quality of the core has a lot to do with it also.
Same with the boots , you can't see them spark off down in that hole . Looks can be deceiving. They are relatively cheap. Buy quality . Belden from napa are good brands .

If you were a high voltage lineman would you stake you life on that boot if it was between your hands and that 30,000 volts you had to touch ?
I replaced all my injectors at 100k as an maintenance preventive . They are expensive . I am at 172k now so at 200k I may change them again ,only quality new ones will do for me . If i can reach 280k I will be happy . I would clean them as f150t has suggested ,its not that hard to set up .
This rough running at idle can be caused by a vacuum leak ,intake gaskets , purge valve etc . I would run a homemade smoke test on her by using a you tube homemade smoke machine . Could be anything including gas cap to fuel pump gasket .
Doing some of this will increase your knowledge 10 fold for sure . Clean that carbon out of the sparkholes also .

 

^^^ I agree @StephenG. If it is that, wouldn't it show up as unbalanced compression between banks. Or if lash adjusters or general lifter/follower slack is affecting total valve lift/cylinder aspiration, wouldn't that show up as an inbalance between cylinders. That's basically where I was headed suggesting the compression test. Not a sloppy one, but good accurate wet/dry check with good equipment and carefully recording results.

 

@redfishtd you hit the enter key before I did. Good points. The OP has a code reader, so he can monitor fuel trims while looking for a vacuum leak using an unlit propane torch or flammable liquid. (little more commonly available equipment). But fuel trims, unfortunately, can't help narrow down unbalanced fuel injector delivery on one bank. The damn PCM will just compensate for a partially plugged one by working the others harder. I'm an advocate of replacing them preventatively also, but wow - I was afraid of rebuilts, and my brand new quality ones were $80 some dollars each!

 

Thank y'all for your responses, I really appreciate the help.

F150Torqued: Is there a good video or instructional somewhere about how to clean the spark plug holes? I don't want to do it haphazardly and knock gunk into the cylinder. Also for the compression test, do I just take it to any mechanic or are there specialists that I have to look into?

StephenG: Is there anything that I can do to diagnose a timing issue?

Redfishtd: I will try to do that smoke test sometime in the near future and see if anything is leaking.

Might take me a while to get all of this done as I am a poor college student at the moment with neither the time nor funds to do repairs every weekend. Because of this, the results of all of these tests might span a few months, but I will post them as they come in. Again, thank you for your responses. Yall are really helpful in guiding my testing and thought.

 

The best ways I know of to diagnose a timing issue is the hot idle diesel sound. Doesn't do it at cold (unless its really bad!) and only at low RPM, usually below 1200ish. Torqued can tell you how to look for it with the Torque Pro app or maybe even possibly with you live data reader if it capable of reading the values associated with the timing system.

 

I'll post another video here soon to see if yall think I have that diesel sound, but I think it sounds pretty normal. Just a lot of shaking!

 

Make sure it's hot. Like drive it from 30+ minutes so it's definitely fully warmed up. Then just let it idle and video under the wheel well, up across the front top side of the engine and down into the wheel well.