2002 Honda Fit Acceleration issues when warm



Hi everyone,
I’ve got a JDM 2002 Honda Fit in New Zealand. The car runs perfectly when it is cold, but shortly after the cold engine light goes out, the engine starts misbehaving… sputtering, etc. under load when I try to accelerate.

I recently replaced all 8 coil packs a few months back to fix a previous engine misfire (and just recently replaced all spark plugs). Now, it seems I’m having issues while accelerating. The engine seems to be down on power until about 50km/h or so and then you can feel the car take off (at least relative to what that little engine can do…). Along the way you can feel periods of a slight shudder, or grinding? or rough running when accelerating from a stop, then again from around 20-30km/h, then again around 40-45km/h or something along those lines. The roughness kind of comes and goes as you accelerate, though it is always lacking power until it seems to “break free” somewhere between 50 and 60km/h.

Shortly after the coil packs were replaced, I noticed this slight shudder for a second or two when accelerating from a stop, but it was very slight and only from when stopped. Now it seems to have gotten significantly worse all of a sudden (as described above).

Probably unrelated, I had to jumpstart the car a couple weeks ago. It had been running fine after that until now. I have already done the ECU/PCM reset procedure and it didn’t seem to make a difference.

I’ve tried to clean out the EGR valve as best I could, and that doesn’t seem to have made a difference.

I’ve got a couple theories, but am keen to hear what everyone here thinks. Thanks in advance for your help!


Have you ever had the valves adjusted?


Got codes? What are they?
There are a lot of possibilities, including but not limited to the temp sensor (which would, if I had to make a truly wild guess, be my guess), but the codes can point you in the right direction.

It’s always wise… and cheaper… to do some diagnosis before you start changing parts. “Shotgun” maintenance sometimes works, but usually only after changing half the engine.


I bought the car at ~154000km and it has ~169000km on it now. In that time I never had the valves adjusted. Not sure what the previous owners did, but I’d guess they didn’t either.

Unfortunately when I tried to pull fault codes from the OBD sensor, nothing came up…


So, getting them adjusted would be a good idea in any case…


another update…
I reduced the spark plug gap to about 0.032" - 0.035" as recommended in some other posts, and that seems to have smoothed out the ride (for now…)

I imagine this ‘fix’ will only be temporary. What should I be looking at to fix it more long term? New coil packs? adjust the valves??


What’s Honda’s recommendation for the spark gap? What was it before you reduced the gap to 035?

I doubt the actual problem is the spark gap. Reducing the gap can be helpful if the mixture or engine operating temperature is incorrect. There definitely is a change in the engine computer programmable function when the engine coolant and the o2 sensors reach certain temperatures. One important one is the o2 sensors come on line. Before they heat up they are ignored. I’m thinking you have some kind of fuel/air mixture problem. The more likely possibilities are – beyond basic routine maintenance stuff being deferred: faulty o2 sensor(s), engine or exhaust system air leak, incorrect fuel pressure, faulty fuel injectors.


Thanks for the thoughts!

Honda’s recommendation is larger. I’m sure the spark gap isn’t the root cause, but it’s a quick and cheap temporary fix for the moment instead of throwing money at a 15 year old car.

Wouldn’t a faulty O2 sensor throw up a fault code? So far I haven’t been able to get any with the OBDII reader.

If by reducing the spark gap (and making the spark weaker?) it makes operation smoother, wouldn’t that mean if anything, I’m getting too much fuel as opposed to too little? Would this reduce the likelihood that the issue is faulty fuel injectors?

Is there an easy way to check for an engine/exhaust air leak?


To test your OBD II reader, you could try just disconnecting the upstream o2 sensor. That should throw a code once the engine warms up. Disconnecting the engine coolant sensor should throw a code too. On my Corolla that throws code immediately after starting the engine. If you get no codes during those tests, there’s likely a problem with the equipment you are using to read the codes. If you have codes but can’t tell, that puts you at a big disadvantage towards a diagnoses.

My first guess would be a problem with the ignition module or coils if reducing the spark gap helps the engine run better. Beyond that, hard to say if it would point to too rich, or too lean.

Honda’s scan tool might be able to do that. Diy’ers would listen for a ffft ffft ffft sound as the engine idles.

That your symptom seems to clear up at higher speeds is unusual. That must be an important clue. A crank position sensor could act like that I suppose. Work better at higher rpms. Or somehow cause the engine timing to go from incorrect to correct at higher speeds. Likewise a cam position sensor. If you had a coil or ignition module problem, higher rpms would normally make it worse, not better.

If you presented your car to a shop and they found no ecm codes, they’d probably put it on their ignition analyzer equipment as a first test. They’d probably also look at the o2 sensor waveforms, check fuel trims, fuel pressure as the effect happens, etc.

Edit: One more idea, the MAF might behave that way, work better at higher rpms and higher engine loads. And a significan engine air leak could cause it, since the air leak would probably diminish with higher engine rpms and loads since the intake manifold vacuum would be reduced, plus the fuel flow rate would be increased, which would tend to mask unmetered air sneaking into the cylinders bypassing the MAF.


The OBDII reader of mine is working fine, so that’s not the issue.

I’ll have a look into those things you’re suggesting.

One more confusing anecdote. It may just be in my head, but it seems the car runs more smoothly in the mornings and evenings than in the middle of the day. Also, yesterday I took the car out for about a 20 minute drive a little before sunset. It wasn’t performing so smoothly. It was parked for about 20-30 minutes. In that time, there was a short and sudden heavy rainfall. The storm passed and we drove back for another 20 minute drive. By this time the sun had set and it was ‘dusk’. On the drive back though, the car behaved noticeably better. Could the humidity in the air have anything to do with it? Or did the rain somehow get anywhere? Colder air temperatures? I’m in a fairly humid environment (humidity levels increase significanly when the sun is down) and at the moment temperatures during a day will range from 9C to 16C.
It all seems far fetched to me though…


When engine performance degrades or improves noticeably with temperature or weather/rain/humidity changes, it is often due to an air/fuel mixture problem. If the air/fuel mixture is correct, the weather won’t affect engine performance very much if at all. Ignition timing, spark, and compression can also be involved when weather changes affect performance.

Just curious, how can you be certain your OBD II scanner is working correctly? Above you say it has never shown a diagnostic error code.


Thanks for that. The OBDII scanner picked up when I unplugged the TPS and gave a fault code. It also gives me a dial indicater of throttle position, etc.


I’m using the Torque Lite app on my phone with the OBDII. There’s some graphs it says I can pick up like “O2 Sensor1 Equivalence Ratio”, “O2 Volts Bank 1 sensor 1” (and 4 sensors with bank1 and 4 sensors with bank 2), and “mass air flow rate”. It also has something called a “Fuel / Air status widget”. Is there something I can look out for with these outputs that may be an indicator of O2 sensors or Mass Flow sensors operating incorrectly but not bad enough to throw a fault code? Thanks again!


a couple other things I’ve tried to take a look at so far with my OBDII reader (using the Torque Light app)…
tried to watch the readings for the O2 sensor, and they seem alright. The graph display shows the reading fluctuating between -0.1 to 0.7V or so, but the dial indicator shows it between 0.1V - 0.8V. I imagine the graph reading negative might be a problem with the app?? Also, when the engine is being revved, the frequency of the signal wave seems correct. At idle it is quite slow, but I assume that’s not an issue.

Those readings were on O2 sensor 1 bank 1. All other O2 sensors/banks were not giving any signal. I was a little surprised because I thought there would be an O2 sensor after the catalytic converter, but the OBDII wasn’t picking it up. I had a very quick look under the car to see if I could see the sensor, but I couldn’t find one… do early JDM fits only have the one O2 sensor? Admittedly my search for the 2nd one was pretty brief.

I checked the vacuum readings the OBDII was giving back, and everything checked out normal as per these references:

any suggestions on what to investigate or pursue next??? Car runs pretty well when the sun is down, but when the sun is up it give some hesitation/stutter issues.

Thanks again for all the help so far!


Not sure what that means.

Bank 1 refers to exhaust manifold. V-configured engines have two exhaust banks, one on each side each with its own o2 sensor, but your Fit only has one exhaust bank, and one o2 sensor.

Does it offer up a parameter called “fuel trim”? If so, that would be the most useful.

Probably an app measurement problem. The pre-cat o2 sensor spec’s I’ve seen are voltages ranging from 0.1 to 0.8. 0.1 means there’s a lot of o2 in the exhaust (meaning lean), 0.8 means there isn’t much o2 at all (meaning rich). In closed loop mode , the computer constantly adjusts the fuel flow so the o2 sensor bounces back and forth between the two. It has to do it that way b/c it doesn’t know directly the concentration of unburned gasoline (HC) in the exhaust. It’s goal is to get the exhaust to contain almost no o2, but more o2 than none at all. I agree that yours seems to be working. At least mostly working.

Sensor 1, bank 1 is the pre-cat o2 sensor. The o2 sensor after the cat would be sensor 2, bank 1.

Check the intake ambient air temperature sensor, and the engine coolant temperature sensor readings.

It sounds like it is running lean. If you can get a measurement of the fuel trim, that would be helpful. Weak spark could cause this symptom too. As could PCV system and EGR system problems. If I had that problem myself I’d do a complete vacuum system check up. That means to use hand-held vacuum pump to make sure everything that is supposed to be holding vacuum is in fact holding vacuum. With modern engines there tends to be a lot of stuff hooked up to the intake manifold vacuum system, so how to do it depends on the exact engine you are testing. One place to start is testing the brake booster, and the map sensor (if your car uses one). They should both hold vacuum to 20 inches of hg. Ignition system problems could be a cause too. Ignition module, crank position sensor, coil packs. Another idea, fuel pressure problem.


I had a quick look at the fuel trim numbers a couple days ago. They were always in the negative. I can’t remember the exact numbers and trends anymore, but it never spiked higher than 0, and I think it went as low as -20 or -25 at times? I’ll probably have another look at it soon.

also, I couldn’t find one of those newer MAF sensors to clean. Just a simple IAT probe. Perhaps my car is too old for the MAF?


My early 90’s Corolla uses an MAP, but most of the newer cars use the MAF. 2002, I guess that’s right on the border, so it might use only an MAP. MAP’s can’t be cleaned. But when in question they should be tested with a hand held vacuum pump to prove they hold vacuum to 20 in Hg. That’s usually a pretty simple test.

-25 % fuel trim indicates an air/fuel mixture problem. If it is holding that range for any length of time anyway. Short term fuel trim could transiently, briefly, move into the -20% to -25% range during rapid changes in engine rpm and load and still be normal I presume. You should be able to measure both long term and short term fuel trims. What does the long term fuel trim say?

The way the engine computer software works, fuel delivery rate is determined roughly using all the sensors except the O2 sensor, the MAF/TPS etc, then fine tuned using the O2 sensor. -25% fuel trim means the engine computer is having to reduce fuel delivery by 25% beyond what the MAF/TPS sensors are saying, b/c the O2 sensor seeing the rough estimate mixture as way too rich. Fuel delivery rate should match up within +/- 10% by either method; i.e. fuel trims beyond +/- 10% usually indicate a problem. Long term fuel trims beyond -20% will usually throw a rich code.

Edit: Misfires caused by weak or no spark can cause a rich lean exhaust condition b/c the intake air and O2 just pass right through the cylinder and into the exhaust manifold, where the O2 sensor senses the O2 and says “lean”. That’s not consistent with a -25% fuel trim, so the problem must lie elsewhere.