Rough Idle, now Check Engine light on?

Update: car sort of fixed itself a little - less rough idling, and CEL turned itself off. Then I dropped it at garage, mech said he WAS able to reproduce my issue, and he replaced the suspect coil that I had moved to #1.

Didn't have a chance to shakedown it afterwards: I still have to verify my ATF fluid level; I had trouble getting a clear reading on the transmission dipstick on my first attempt. Will probably get a chance tomorrow to drive a bit, check the idle, and also try again to put a pin in the ATF job.

Yeah, he blew me off for a day or so but then he got to. It, and no charge of course for the coil swap. (I now know that that is only about a 2-minute job if you take your time with it, so.)

No way I was going to pay for new sets of coils & plugs - that's what he just did about 10 days ago and he got me for a big $$ ticket on that with the diagnostic etc. I don't even want to tell you what that bill was, but it tamed the wildest of misfiring at least. I was worried he might want a new diagnostic $ but I guess he just went with my logic, maybe he didn't even spend time reading the codes once he was able to confirm the misfire?

Hopefully things will settle down now.

With the dipstick - I got everything warmed up with a short drive and running through the gears. The ATF looked low (the front & back of the dipstick did not agree, I went with the low side) so I added about a half a quart. After that, I think there was still fluid in the dipstick fill tube - I kept getting a line of ATF along one edge of the dipstick, and patches of fluid in different spots. I must need to wait more and let the fluid flow all the way in after adding some - I was impatient I guess. The Fusion manual says to keep it running while you measure, which I did, and I've been told by a couple of Ford-centric internet commenters to get it full warm before checking the level, with a real 10-20 minute warmup drive. Next time I'll be sure to let it flow into the trans if I add any more fluid, I think that was the part I did wrong.

Good test-drive today. Mix of stop and go traffic and highway up to 70 MPH or so. Only the mildest vibrations when stopped, nothing like it's been. Good news!

Now I have to sort out the ATF - I think it was actually quite low before I started, it has read low so far as I can tell after my two drain & fills, where I replaced the same amount, I drained. Since then, I've added about a quart and a half, I'll re-check the level tomorrow.

I need to figure out whether I left the drain plug unsealed? Or if there was actually a fair amount of seepage before I bought it? Or I'm reading the level wrong?

Going to look in the belly pan for evidence of the drain plug being leaky (I don't see evidence under the car though.)

Here's where I stand, with a couple of questions thrown in:

Two good test drives since the suspect coil was replaced. No kicking at a standstill, everything seems normal all the way up to high speed. Very slight periods of very slight vibration while stopped, this seems normal. I'd say I'm completely sure it's completely fixed but for one piece of info. I just got hold of AndrOBD, a very nice free/open-source diagnostic app for Android. It has the feature of showing misfire counts, not just fault codes. I have been told that this era of engines can have a fair number of misfires before setting a code. I would suppose that the count the app shows is the total on all cylinders.

After about a 20-minute ride I saw about 20 misfires counted, no fault codes. Is that a lot? Is that a red flag? I've also noticed that my coolant temp still never gets above 180. But the idle does change to a lower RPM (950 goes to 750) once the engine warms up - so that means my thermostat is working, right?

I also drove around a bit and rechecked the ATF with the dipstick - no problem reading it this time. It was reading just about perfect - between the upper hole and the top line. I poured in about another pint. I'll look at it again in 25,000 miles if I ever get there. I'm not really as worried about leakage anymore but next time I'm under the car I will take a close look. (I have some black vinyl wrap I plan to chrome-delete the three upper grille bars and the lower grille surround with; that will require me to go up on the ramps at some point.)

Feeling pretty good about going ahead with the ATF service, I think it seems pretty clear it was warranted what with the low level and the 100,000+ miles.

I will grab a can next time I'm in the auto parts store. It was maybe 40 degrees while I was driving - cold but not extremely so.

Hmm okay. So, I would change the plug in 3 (where I had the problem for a little while) then? Not 1 (where I only had misfires while I was troubleshooting, relatively short time)?

I don't think I get any data from this tool on *which* cylinder is misfiring until it reaches the threshold to send a code, the "Misfire count" is just a single number which I think is a total.

How important is it to get a plug that's exactly identical to the other 3?

All this, assuming the additive plus the "Italian tune up" doesn't fix it.

That VGG guy seems pretty entertaining - I'll check out a few more of his videos, thanks. I landed on one about a rat rod Chevy C10 pickup that was pretty messed up but also pretty cool.

A couple of cans of B-12 are on the way. Free shipping=taking the slow boat, so it'll be a little while before I get a chance to use it. Any downside in doing, say, two consecutive tankfuls? It was quite cheap to buy two off Amazon.

What would you say to opening up and cleaning the electronic throttle body on this car? It seems that there was once a replacement extended warranty on that part for this engine but I'm late to that party. It was only for cars exhibiting symptoms, though, so I guess that's a good thing.

I will say the slight vibration at idle seems to be improving each time I drive it - been lead-footing it whenever traffic permits. (I always do that anyway but now I have an excuse!)

"Berryman's first." - 2x? Okay? Or just once and stop fussing with it?

What I've seen online about cleaning the throttle body on this year's Fusion is: disconnect the battery, remove and clean the throttle body, reinstall it, bleed the capacitors, and then reconnect the battery and go through a re-learn routine. FordTechMakaluco (among others) shows this process. No computer commands required. Sound okay to you?

I have some general knowledge about electronics, I'd personally drain the caps through a resistor rather than shorting the car's + and - together, it'd give a thorough but less sudden discharge. I have plenty of 5W resistors here I could use with no fear of blowing them up. Maybe 1K - 10K ohm, something like that.