I'm looking for advice on the next step for my stuttering problem. (No, I don't need a speech therapist.)

2008 Honda Fit Sport automatic, 93,000 miles.

Symptoms:
1. Stutter at idle (and occasionally while running, but not often)
2. No check engine light comes on, ever. No pending or current computer codes.
3. One time the car actually died

The problem started a few thousand miles ago. It was mild at first and gradually got worse. Here's what has been done so far:

1. Cleaned throttle body (no help)
2. Replaced spark plugs (no help). New plugs are laser iridium (don't know brand)
3. Replaced air filter (no help)
4. While the car was running, I removed each ignition coil connector one at a time. As expected, the car continued running with one connector removed at a time, but the stutter didn't occur. RPM dropped 10-20%. It should be noted that this RPM reduction is NOT what happens during misfires (at least not on a sustained or noticeable basis).
5. I wiggled the coil connectors and wires around with the car running to try to induce the problem (testing for bad connector at that point). No change.
6. I bought one new ignition coil on the optimistic hope that only one might be bad. I replaced them one at a time (left to right while facing the front of the car). After each replacement, I started the car, heard a misfire, and concluded that the replaced coil wasn't the problem. On the 4th (rightmost) one, it didn't misfire immediately after replacement. Although it does run much better, it still misfires a bit on every trip. (After a couple of days I took out the new coil and put the old one back in for a day, just to confirm that I didn't imagine the improvement with the new coil. This confirmed the old #4 really was bad.)
7. I tested the resistance between pins 1 and 2 on each ignition coil and found the following:

1. New coil: 1894
2. Old coil #1: 1841
3. Old coil #2: 1803
4. Old coil #3: 1822
5. Old coil #4: 1799

8. A mechanic monitored the fuel trims while running, and they were good.

I find it interesting that although the resistance measurements of the four coils are similar, the clearly bad #4 coil has the least resistance, and the new coil has the most resistance. The three remaining old coils have resistance values closer to the bad one than the new one. I don't know if that means anything.

Here's what I've learned from this experience so far:
1. Ignition coils do not necessarily go bad all at once. Otherwise, the car would perform the same with the old #4 coil as it does with the #4 coil removed altogether.
2. The old coil #4, although partially functional, is bad enough to contribute significantly to the problem.
3. Something else is wrong in addition to the replaced coil #4.

In searching forums here and elsewhere, it seems that this problem is usually attributed to bad ignition coils or bad valve clearances.

So it seems that my next steps are:

1. Give up on my hope of only having to buy only one ignition coil, and go ahead and replace the remaining three. (Cost: US$141 and 15 minutes labor)
2. Do a valve job (Cost: $21 for feeler gage and head cover gasket, and probably most of a Saturday since I've never done it before--but it looks easy enough based on )

I'm inclined to replace the coils first even though they cost more, because it's super easy and they'll probably go bad soon if they aren't already. (And while I'm buying the 3 coils I'll go ahead and buy the valve job supplies since that should probably be done soon anyway--it hasn't ever been done before I don't think--and a Haynes repair guide.)

Any of you guys with more experience than me think I'm on the wrong track?

 

Most likely one or more of the coils causing it, pretty common on this car

 

Did you remove the battery cable or clear codes even if there is none to erase the learned timing and fuel control? The ecu will relearn in a few days and if there is a problem that it cant codes will appear. You can look under Idle relearn procedure but its not really a idle relearn. The fuel trims go to zero and the timing goes back to -15 and relearns all conditions that you operate at. The long term fuel trims wont start to move for about 20 minutes. It also erases learned knock control which wont go back zero unless you reset the ecu again. I do it in all time in my Honda and Acura cars with zero issues except a better running engine and better mpg.

I would adjust the valves and clear the ecu and see what happens. When was the last trans service too? I would do that too. All these are required around this time. The ecu reset should have been done when the throttle body was cleaned. Was there burnt contacts on the coils primary and secondary which is the plug boot to plug and coils?

 

Regarding erasing learned timing and fuel control: I have no idea. I've never removed the battery or cleared the codes. (I don't have the equipment to clear codes.) I'm certain mechanics never removed the battery cable, because I've never gotten my car back from them with all my radio presets etc. screwed up. Are you saying that after doing the valve job I should disconnect and reconnect the battery cable to reset the ECU?

Transmission service was within the last 20k miles. There was no damage to the coils of any kind, including no signs of burning or gas escape.

 

Get the valve adjustment done honestly, you'll love the car when it's done.

 

On my car coil #4 started failing to fire (once per day) giving car significant jolt under load (idling in drive); coil #3 did it as well once per week. I replaced all of the coils (the remaining coils were eroded badly. While I saw one car on the junk yard with Bosch iridium plugs I suggest using original brand plugs for Fit.
The "fuel trim " is affected only if there is a constant misfire

 

No significant difference but more torque when cold in a cold weather

 

Yeah... don't be cheap or lazy.

Replace ALL the coils, adjust the valve clearances.

 

To echo what others have said, adjust your valves and see where you end up. You may find they're out of tolerance enough to keep some from fully closing/opening. I did my first adjustment last month at 190,000km's (yep, should have done it 3 times already, *ding ding* "Shame") and found the exhaust were slightly tight, and intake were slightly loose. It runs much smoother now and seems a little more responsive. I have not replaced a coil yet at 195,000 kms, and it runs like a sewing machine. (For what it's worth).

It's a really easy job to do. I wouldn't suggest you get a valve job done until you've adjusted your valves, and tested the compression to make sure you even need it 👍 No sense doing all that work/spending a ton of money for nothing. Do a compression test before deeming your valves "bad" would be my recommendation 👍You'll likely be able to see if anything looks off when you pop off the rocker cover, mine looked brand new (which ended my dreams of swapping a k20 in....for now...)

 

First +1000 on adjusting the valves.

A compression test is just a first indicator, anybody that uses one to decide on a valve job is cheating themselves, a LEAKDOWN test is the only way to really know whats going on short of pulling the head.

The FIT motor needs regular valve adjustments no matter what Honda says.
Its easy and makes the engine run like a watch..

A leakdown can be done with a compressor and a leak-down gauge set which costs usually <100 bucks(Unless your a snap-on junkie) .


This one is 67 bucks.

its best to use 100PSI because then the math on the percentage of leakage is easy in your head. Ideally any healthy motor should not be over about 10%, less is better. Your rings are not seated at 100 PSI so there will always be some leakage.

Good luck.

 

Bingo. Good call. But a leak down tester isn't necessarily needed if he's just checking to make sure his valves are seating correctly. I do completely agree with you though

 

 

 

i wonder if i have a misfire issue now that its common for the engine to do so without codes or CEL.

Even the stealership was like "nah you do'nt need a valve adjustment!" even though i wanted to get it done under preventative maintenance lol