@Sporttwelve : "​​​​​Just joined this community (even though I've visited several times and gleaned super helpful information based on what others have experienced and tried). My 2012 fit sport has a brand new OEM alternator (as of January 2024) but now I have another issue. CEL flashing and I get "cylinder 3 misfire" as well as "injector circuit open". Just replaced all four spark plugs, ignition coil (3) and fuel injector (3). Unfortunately, problem persists. Any suggestions on what could be continuing to cause the issue? I appreciate any insight you can offer me."

 

Could you kindly clarify on the order of events?
Sounded like: New alternator, then misfire on cylinder 3, then replaced all 4 plugs, cyl 3 coil and cyl 3 injector. Is that how it went down?

Things that can cause your misfire include the above, valves (seems unlikely it'd just be cyl 3 and after an alternator replacement, but possible), head gasket (what's your mileage?), and uhh.. Cheesh, a cylinder head crack? Maybe an old one in the plug hole, the result of an ejected spark plug repair gone sour. Or computer stuff. Or rodent damage somewhere.

I'd like to double-check the alternator installation, brand, ratings first, just to put that behind us.

 

Thanks so much for your reply! Yes, you're absolutely right that's exactly how it went down. The alternator (Honda brand OEM ~ it says Honda right on it) was installed in the beginning of January.
This misfire , circuit open issue just started about a week ago and I took to my same mechanic who recommended spark plugs and injector. He also ended up having to replace one ignition coil (circuit 3 same as the injector). I know he said he was getting OEM spark plugs but I'll have to ask tomorrow what brand I've got in there!
Oh man, I truly hope it's not some kind of a rodent issue!!

 

Oh, and she's a 2012 fit sport MT . I've got about 122,000 miles on her.

 

If I'm not mistaken, someone on this site makes the claim that in the fit, one must also replace all four coil packs whenever doing the spark plugs?!! Perhaps I should ask to have that done?
I also remember seeing something about 0.44 gap instead of the factory 0.51 ?

 

Okidoki -- So the alternator replacement is pretty well removed from the misfire. And your mechanic went through basic stuff of swapping out your coil and your injector. Did he say there was anything wrong with the old ones? I mean, it's worth a shot to try replacing those, but those can both be tested with a game of musical chairs.
Regardless, those are the two most straightforward solutions ruled out.

If those were both intended to address the misfire, then maybe your mechanic would give you a break on a valve adjustment (since you paid for two solutions that didn't solve anything). Did your car present any other codes besides the assumed one for a misfire? Or.. Did it even give a code for the misfire?

And like. How bad is it? How well does the car idle/drive with the miss, and is it constant, or intermittent?

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EDIT: Do you remember when the misfire started? Like, first start of the day? Or after a heavy rain day? So on ~

 

Oh man! this is like a chat room 😂
If you've got non-oem spark plugs, then the gap may be non-oem. Depends on plug design. But I'd reckon if that was your issue, you'd have it wrong on all cylinders. I'd have to check the manual for the stock plug gap, but if you got iridium plugs, which may be OEM, you dont gap those. As for doing all the coils at once, I'm sure opinions will vary.
If one actually was the culprit, yeah, I'd do all of them. Cuz they've all been running just as long. That's kind of like having a single lightbulb go out on a ceiling fan. The others may still be going strong. What determines whether you change 'em is how hard it is to get at the fan, and if you've got or can get new light bulbs
Maybe one had some poor soldering in it, or the filament didn't get made quite right.

May catch some heat for that logic, but I think it's equally valid along with the more cautious approach.

 

I was thinking about that, too(valve adjustment). He specifically said that one was the only ignition coil that was jacked up , the others were in good shape. Sort of made sense to me since the codes were "cylinder 3 misfire along with injector circuit 3 open" so, it feels like the 'issue' may be stemming from that area.
He said the spark plugs actually didn't look bad but regardless I wanted to do that routine maintenance.
CEL flashing started on the Tuesday after Memorial Day (my memory is failing me if we had rain or not but it wasn't raining that day.) Started my car and ran her for maybe five minutes or so, left the house and noticed within five minutes the car was super sluggish as well as CEL flashing. VSL light came on after that too. I drove straight to mechanic and haven't driven since (only home that day from mechanic and back to drop car which is roughly ten minutes from my house).
It's not able to go above 25 RPM (per my mechanic today after work was completed). I do recall feeling like she was dragging butt and wouldn't really accelerate upon hitting the gas. I'm not too keen on driving her with the misfire particularly out of concern that it'll damage my catalytic converter or engine.

 

The more cautious approach is always logical in my opinion although I haven't always taken it but, I agree with your logic!!
​​ Unfortunately, I also need to factor in the cost (of replacing just one ignition coil versus all four) considering I'm also having all four spark plugs put in along with doing air and cabin filter (why not ~ again routine maintenance!) At this point in time, my car is all put back together so, technically, he'd have to open up the area again in order to replace the other three if I were to go that route.
Come to think of it, it did rain on and off the day before this happened (if it makes a difference)!
Your input and suggestions are much appreciated!! I enjoy learning about this stuff and wish I had paid more attention when my father was trying to teach me!

 

I may have missed this, did your mechanic swap the coil pack/plug from cyl three to another cylinder?

 

In our present age, we can learn anything we want at any stage of life. My pop may have had a lot more fun and freedom in his day, but I sure do love all the knowledge at our fingertips. I'd hate to be without it.
That said, I wish I paid more attention when he took me along on HVAC jobs. 😋

Well, from the additional information provided it seems reasonable to rule out a big puddle soaking damaged wiring, yeah?
And.. sudden onset, and severe, too. That'd lead me to suspect electrical, but then you've got a new coil..
If you really want to get to the bottom of this, why not have the gent do a compression test? I'd sooner pay for that and pursue the problem than throw injectors at still-functioning cylinders. I get having a budget, believe me. The compression test could tell you if you have an issue with the cylinder holding compression for any reason: valves, rings, head gasket, or even spark plug threads.

I wouldn't expect a mechanical fault to suddenly pop up though..

Oh, here's a fun idea. Radio interference. this would bring you back to considering ignition coils. Fire up the car, let it warm up (or not, if it sounds too worrisome) and give the throttle a good few hard revs in idle. If it drops out. If the gauges in the dashboard sweep. If it stalls. Or just.. if it seems somehow worse. That could be indication of a failed capacitor or capacitors in one or multiple ignition coils. Coils amplify the juice/electricity of the ignition system to give spark plugs a wicked strong jolt. I don't fully understand 'em. They're like a battery, but.. not quite. but when they go out, you get radio interference. And that can screw stuff up in a super weird way. The harder you rev, the more interference you would get. Think that's just because it'd be doing its thing faster.

 

mmm. the ignition coil interference theory fits with your speed limitation.. fits with replacing one coil not solving the fault. sudden onset too, I think. Your mechanic likes the idea of doing all the coils.. and you did get a coil specific code. So yeah, it may well be worth a shot!! At least run the idea by your mechanic. Ask for thoughts on that, or if he thinks a compression test is in order, or some wire chasing I guess.

Compression fits well with its being one cylinder.. iffy with sudden onset. well with the coil replacement not fixing the problem.

Okay. 1: electrical interference. 2: wire damage. 3: compression issue. and the car's computer always comes dead last in diagnostics. because then you're questioning whether the errors you're getting are even legitimate v. manufactured by a bad brain.
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I feel pretty good about this. it *should* be solvable.

 

I did not ask this specific question therefore, I don't know for sure if he did do that. He did say that he looked at (he may have said tested) the other coils and they were all good. I'll be sure to ask him directly though!

 

Well said!!
I'll ask about the compression test along with the additional three coils. No doubt he'd be happy to oblige!
I highly doubt anything regarding puddle damage since I didn't even go anywhere in my car the day it did rain and it wasn't pouring or anything. We have had a fair amount of rainy days (as usual) this spring, though.
Let's hope and pray it's not a computer issue, right?!!
I'm with you on this being something that "should" have a fix! What that fix will be remains to be seen.
Trust, I will update you as I know more and see what we come up with.
I can tell you that when it's idling, it's only somewhat rough and it seems to level out when I step on the gas (not driving but, idling). Radio interference or probably not? I have no idea on that one but, perhaps not since it seems to run smoother when I give her some gas in park.

 

I'll be SO devastated if she turns out to have a "bad brain". I ended up having to get rid of my last vehicle due to an electrical issue that became virtually impossible to locate or repair. She was getting up there in age really past her time so, I wasn't terribly heartbroken; however, I think if my fit had some kind of a computer or severe electrical problem at this point it would feel insurmountable.

 

I think that rules out radio interference! My (albeit) limited experience with it has assured me that more revs means more problems. We may well be safe to rule out ignition coils!

Yeah, if you can, definitely post up what your friend, the mechanic, says! I'm admittedly excited to know.

And try not to worry too much, yeah? once there's a diagnosis, then options can be looked into. I really feel like the shop should be helping you out at this point though.

 

I didn't read everything, but cheap coils could cause that problem I guess.

Honda OE coils or Hitachi (I think they are the OE brand for Honda - you can search this forum to make sure) are the way to go to avoid problems.

 

Check if any vacuum lines got disconnected. Check 02 sensor connector/wires. Also check MAF sensor is connected/clean, air filter etc. Lightly spray a little water on the throttle body gasket and around the intake manifold gaskets, just checking to see if there's any vacuum leaks

 

Your problem doesn't sound that difficult. It's either a signal problem or an injector (perhaps injector signal problem). Use an old plug and the old coil to see if the cylinder is firing. Leave the new plug in stalled. Plug the wire to the number three coil to the old coil out of the car. Ground the old plag installed in the old coil and check for spark when running. No spark, then wiring problem to coil three. This assumes that old coil three is good, which is a good bet since no change in three misfire with new coil installed. Best of luck, Clay

 

At this point (because he's a smaller shop without tons of diagnostics equipment), my mechanic thinks I should take it to the dealership for a diagnosis. I like staying in one place so, this doesn't thrill me; however, maybe he's right? I asked him how he is so sure they'll be able to tell me what the cause of the problem is and he said because they have all the advanced tools to decipher. 😔