The car: 2008 Sport, 5-speed Manual Transmission, with 70,000 miles.

The problem: occasional hesitation and misfiring. Not every time. But enough to make me feel a little nervous.

There may be a correlation, or maybe not, but recently, I have experienced the problems when I have used regular gas, and the problems magically disappear (and the car returns to its zippy personality) when I fill up with higher octane gas.

The back story, if you have the time:

I have had the car for only 6 months (bought it used).
I had no problems until about a month ago, when the engine light came on and the car was ran with major hesitation. At that time, a shop replaced the air/fuel ratio sensor. The car seemed fine for a day, and then I started experiencing different problems – the problems listed above. At one point, the engine light even came on again, flickering with a bad coughing fit of misfiring. Things settled down with some Lucas gas treatment and some HEET dry gas, but the problem still lurked occasionally when I'd step on the pedal. Then the problem then magically went completely away when I filled up with 92 octane. When it came time to refill again, I tried regular gas (87 octane, from Hess), and I could feel the problems start again, immediately. Again, I added some Lucas stuff, and the problem decreased, and then today I just added some 89 octane gas and the car feels great.

Any clues to what might be going on?

A dealer mechanic said it could be a coil about to go, and he checked two of them and they seemed fine, but he said he couldn't say for sure until an engine light actually came on! I'd rather not wait for a breakdown to happen if anyone has some clues.

Thanks.

 

Sounds like coil packs to me.... Search the "misfire" or "hesitation" and you'll find a lot of info on it.

Once you've resolved the issue, please post back on here to let us know what it was.

 

Question:
I have seen the discussions about coil problems related to a rough running engine,
but are coil problems ameliorated with higher octane gas or gas treatment?
I wouldn't think so, but I don't don't know too much about cars built after 1972.
I thought the octane clue might help identify the issue.

... and yes, once I have resolved the issue, I will certainly post back to let you all know what it was about!

 

I don't think so BUT I do think the dealer mechanic was correct in saying that it is a coil pack/s on the way out. I think the easiest way to find out would be to ask a Fit Freak member in your area to simply swap coil packs with you just so you can test out and see if, in fact, you have a bad coil/s.

 

It worries me that the mechanics are just replacing parts with out finding out which ones are bad. The 02 should last 100,000 miles at least unless there is a code. The dealer should have hook the car to the brick which is a diagnostic scope gauge. They could see the firing order and voltage to each of the coils.

You can take out each plug and check to see which one looks bad. It sounds like carbon build up but there might be a coil problem but not necessarily a bad coil. Look at the coils for burnt boots. The EGR might be stuck open or the map sensor might not be working right. Check for vacuum leaks and clean the throttle body. Do a ecu reset by removing the positive cable from the battery but dont forget the radio code. The fuel filter might need to be replace too.

Check this thread out https://www.fitfreak.net/forums/fit-...tutter-21.html, The last few posts is probably the main reason to coil problems and most likely affect the knock sensor causing the motor to run rich causing the rough idle and other problems.

I have always used premium and my Fit got great mpg here in Chicago. The mpg was very consistent and the same with the Civic.

 

Thanks for the tips on various things to check and clean.

To address your point about the mechanic (quoted above), when the engine light came on, the first mechanic did run an engine diagnostic test. The code that came up called for replacing the air/fuel ratio sensor. But I have to wonder what might really be going on, since it seems to me to be a strange coincidence that shortly after this "fix", a different kind of problem cropped up.

I apologize if my leaving out this part of the story led to any confusion.

 

No problem, Hope my suggestions help you. I am leaning on carbon build up. Do the ecu rest too. There might be a code that pops up and then you know what to fix. It also rebuilds the random access memory which stores fuel trims and timing and knock under different conditions. Check the tail pipe for sooty black powder. That is a sign its running really rich. There will be some but if its rich your finger tip will be solid black.

I just got rid of my wife's Civic because at 20000 miles it only got 22-25 mpg and the Highway was the same. No power and steering problems too. Premium made it run better but the mpg did not come up like mine. I get upper 30 lower 40s all the time in my Civic. My Fit got a little better in the winter but lower in the summer compared to the Civic. 37 Fit compared to 36 Civic mpg life time.

 

One more suggestion, do a load test on the battery. Low voltage will cause all sorts of problems.

 

After many hours of web searching, your problem comes by far the closest to mine.

My car runs OK when cold, but after about 30 minutes of driving (maybe more, depending on how hard I'm driving it) it will start to misfire, at first only at high revs, then gradually at lower revs until it misfires whenever it's under load, ie. accelerating or going uphill. If I gun it, it will choke and buck. This all started quite recently.

The mechanic said it was a faulty ignition coil, but because the problem doesn't happen when the car is in neutral, he couldn't identify which one. He also said that the battery was weak, which might contribute to the problem.

So anyway, I replaced all 6 coils, and the battery, but the problem was still there, exactly as before, and I was a few hundred bucks poorer!

So a couple of days ago, I went for a longish drive. Sure enough, about 30 minutes into it, the car started to misbehave. As I was low on fuel, I stopped to fill up (and before anyone says anything about low fuel, it happens on a full tank too). Just on a hunch, or in desperation, I filled up with high octane fuel. When I took off, the problem seemed to have gone!

I kept driving for another 20 minutes, over some hilly terrain, and I drove pretty hard. Nothing!

So now what? Like you, I'm hoping that the octane clue might shed some light on the cause, but I have no idea what the connection might be. If I find out before you do, I'll let you know.

I've put a dose of injector cleaner/carbon remover in the fuel tank, and after that I'll try going back to regular fuel.

 

I thought Fits had 4 coils or 8...

The only times I can think of where premium fuel would help is if you are getting pre-ignition, your cylinder temps are getting out of control, or your compression is being raised. Carbon can be a source of pre-ignition. Maybe have your engine scoped through the spark plug hole to see how the cylinder looks. Also some SeaFoam run through the intake might help with the carbon build-up.

Normally premium does not help anything on a regular gas engine. It is harder to burn and has less energy density.

 

Your problem sounds exactly like mine. It gives me solace to know I'm not alone or hallucinating with respect to these issues.

One more month of investigations later (visits to two mechanics), and I will am still turning up without any answers.

I'm sorry you spent the dough w/o any remedy, but perhaps that helps hone in on the issue.

Without the engine light coming on (and there's no history report), both mechanics couldn't identify the problem.

One mechanic suspects it's a fuel issue of some kind (injectors?), rather than an electrical issue (coil), or a mechanical issue (hydraulic ...?), but without the engine light coming on and staying on, but he said he'd need a diagnostic machine that can do an "event freeze."

I did find that sometimes with higher octane gas, the problem immediately "disappeared," but I think even with that, I may have experienced a "return" of the issue after some driving time. I forget. I'll have to pay better attention and track it again.

The gas additives (Lucas and Seafoam) seem to make things quiet down for a bit, but then the problems seem to return. I did not try Seafoam in the intake, nor have I had someone check for carbon in the cylinders.

I will certainly let you all know if and when I find the answer, and will you please do the same?

Thanks!

 

have you checked/replaced spark plugs?

you definitly have a misfire (or multiple misfires) since the check engine light flashes at you. you shoudl have teh ECU codes pulled and hopefully it will tell you what cyclinder has the problem.

being that a different ocatane fuel "fixed" your problem though, im betting on spark plugs as the problem.

 

Thanks for the input.
A dealer mechanic found some misfiring on cylinders #1 and #4, and inspected the plugs and coils on those cylinders, and they seemed fine.

Unfortunately, even though the engine light has flashed on two occasions now, they have not registered in the computer history (!).

Please keep the clues and possible solutions coming ....

 

for the cost of new plugs, just replace them. it takes 10 minutes and will eliminate one problem. at 70k miles they are nearing the end of their life anyway. search around and you can get soem for $35/for 4

 

I agree with NIGHTHAWKSI, new plugs may help. I just changed my second set at 75,000. In my case, the new plugs did the job. Although the plugs are advertised to go 100K, that is probably based on "normal" driving. If you take your revs up like I do, it makes sense that the plugs are going to wear sooner.
When I pulled my IK22s at 75K, the ground electrodes were rounded and eroded to the point that I could not reset the gaps accurately.

Notice the rounded, and misshapen electrode:


Notice the sharp edges, and flat. parallel contact surface of the ground electrode:


From what I've read, the sharper edges are more conducive to a more efficient spark.

 

Ok!

I will replace the plugs sometime this week and tell you all how it goes.

At >70k miles, seems like it's a good thing to do anyway.

I'll keep you all posted ...

 

Engine Misfire Diagnosis

 

Whatever he did to see the misfiring on cylinders 1 & 3, he needs to do it again after swapping those coils with 2 & 4. This is how I was able to narrow down that a coil was the problem. But my coil was nice and after some intermittent problems just up and died.

And I agree with everyone else about changing the plugs just to eliminate any issue there. My car had bad plugs and a bad coil when I bought it (with 130k+). But the plugs would have complicated the issue if they had not been replaced with the correct ones, non-oem ones were installed and they had damaged electrodes!

On a side note, an UltraGauge might make your journey a whole lot easier. Before your engine light starts to flash, the gauge will tell you there is a pending trouble code. You can check it immediately and find out which cylinder is giving you problems. If the detected problem goes away before you can check it, the ECU will eventually decide to get rid of the code. Having the UltraGauge was instrumental in figuring out my problem quickly. Even though I bought it for gas mileage reasons, the pending and stored trouble code ability was priceless.

 

I would check the battery, EGR and plugs first. Not all misfires are coil problems especially if it only happens when the engine is hot. The Ultra gauge is the best add on I ever bought and paid for it self in a few months.

 

Update:

I replaced all spark plugs and the problem has gone away (for the time being - fingers crossed). But not immediately.
That intrigues me.

See details below, and please tell me what you make of them:

What was checked and done:

1. Battery checked OK.
2. Replaced all 4 spark plugs with the best I could buy (Laser ??)
3. Added some dieletric grease on supposedly beneficial spots
4. Did not check EGR valve or Fuel Filter b/c mechanic said they were not easily accessible and required more labor than I wanted to pay for at this time.

1st day:
4 instances of the misfire/hesitation/bogging, but they were not as intense as the instances in the past. This happened over the course of 150 miles of driving, over a 3 hour period that included several stops. Each time the misfire happened, I was in 5th gear, 55-58 mph, at 2,800 rpm, and hitting the gas to accelerate. Sometimes I was going slightly uphill (some load), and sometimes it was on a straight. It only happens when I depress the gas pedal more than just the usual light touch that is required to make her go. These instances didn't seem to correspond to any warmup time.

2nd and 3rd day and counting:
No real discernible problems over 400 miles of driving. Sometimes I'll sense a little hesitation or lack of smoothness, but it could be my imagination.

Halfway through day 2, I refilled with regular gas (Mobil, 87 octane, no additional gas additives). Towards the end of day 3, I refilled again with the same gas.

I am curious why I would continue to have the problems on day one (albeit much less acute and dramatic), and then no problems after that?

Maybe some carbon got burned out with the fresh plugs?
Does the computer do some kind of adjusting or readjusting to conditions?

Thanks.