Hi there,

I am having the same problem with my 2007 Fit Sport AT with 80k miles. It hasn't had a valve adjustment in the 40k miles that we've owned it, so maybe I should take it in and have that done. As far as I know, the service manual doesn't say it should be necessary yet.

When stopped at idle it feels like it is going to stall, but only sometimes this happens. At maybe 50-75% of the stop lights the engine struggles and nearly stalls then it recovers briefly and then often nearly stalls again. I'm assuming the computer is detecting the low RPM and compensating the idle?

I just drove it around for 15 minutes tonight and also noticed what feels like slipping and/or "sluggish acceleration" in 1st gear after being stopped. The Fit is usually pretty zippy in 1st (due to its low gearing?), but today it felt like it was struggling and lurching to accelerate from a stop. From 2nd gear upwards there are no issues and the car drives normally.

I already checked the coolant and oil and they seemed low but not excessively low: I added some of each to get closer to mid-range in the min/max markers. The transmission fluid level seems fine (and probably wouldn't cause the idle problems), but its dipstick is hard to read accurately and of course varies with temperature.

I'm not that knowledgeable about cars so don't construe any of this as advice. But my next though would be to (1) do some Googling on the airflow sensors that someone else mentioned and (2) check the easily-replaceable electrical stuff like the battery and spark plugs. We have run down the battery twice in the past year through user-error, and since it has just started to get cold in Northern California, maybe that is the culprit.

If I figure out a solution, I will post it here.

-Paul

 

sounds like spark plugs if its not constantly crappy

 

Following up on my previous post with the solution.

TL;DR: It turns out that the 2007-2008 Fit ignition coils tend to go bad around 80k-100k miles, according to numerous online reports (such as the customer reviews of the ignition coils on Amazon). Replacing them solved the problem on our 2007 Fit Sport AT with 80k miles. Total cost for 4 new coils is about $200 and 1 hour of your time. I am reporting this after driving the repaired car for 1 week with no lingering issues.

Note: some people call the ignition coils "coil packs" but the manufacturer calls them each a "Direct Ignition Coil", part number 178-8374.

Recap of the symptoms:
The problem was an intermittent rough idle, worse when the AC is on, as well as stuttering and hesitation during acceleration. Under higher load (meaning faster acceleration and/or more people in the car), we started to get more of this rough engine behavior, and eventually some misfire codes (any combination of P0300, P0301, P0302, P0303, P0304 I believe). The check engine light flashes when a misfire condition is actively occurring, and stays lit thereafter. The car is drivable but should be repaired ASAP, and it tends to lack power on the highway and when accelerating.

Solution:
I initially replaced only the spark plugs to see if that fixed the problem. They cost about $11/each on Amazon and I used the relatively high-end spark plug socket below, which worked amazingly well. The combination of removing and reinstalling the distributor coils made the problem worse (and I probably used too much dielectric grease), so I then ordered 4 new ignition coils and replaced them, which solved the problem. The name brand version of ignition coils sold by Amazon cost about $48/each as of right now and you need 4 of them. Before you install them, you should watch a video that shows how little dielectric grease should be used: it is just to lubricate and seal the ceramic part of the spark plug and shouldn't be used on any of the electrical connections.

In my case only the ignition coils were necessary! You might save money if you replace the ignition coils first instead of trying to replace the less-expensive spark plugs first. The spark plugs I removed from the car actually looked fine and probably didn't need to be replaced yet. Having said this, you will have access to the spark plugs when you remove the ignition coils, so if you're ok spending the extra $40-$50 and replacing the spark plugs, it is convenient to do so at the same time.

The installation process is fairly easy and I will summarize it below. It will take you only about 1 hour, including collecting all the necessary tools and parts.

1) Disconnect the negative battery terminal (10mm).
2) Disconnect the connectorized wiring harness from the ignition coils. There is also one small electrical connector on the top right of the harness which you can disconnect to aid in bending the wiring harness out of the way of your tools and hands during this process.
3) Remove one screw on the left-side (12mm) and two on the top of the engine cover (10mm) which hold down the wiring harness. This will allow you to bend it out of the way of the coils and access their retaining bolts with a socket wrench.
4) Remove one retaining bolt and its washer that holds a corrugated hose to the firewall (10mm). This is only necessary if you need to do so to give your socket wrench clearance on the rightmost ignition coil.
5) Unbolt each of the 4 ignition coils and remove them (10mm). Work left-to-right since the left one is easiest and you'll get a feel for it as you go.
6) Optionally replace the spark plugs (5/8"). (See other webpages for instructions). Don't over-torque them! Nothing is required to be applied to the plugs: the NGK spark plug threads should not be greased in any way.
7) Put a tiny dab of dielectric grease on the inside of the red or blue cup of the new ignition coils, spread with a Q-tip, and reinstall them on the spark plugs.
8) Reinstall all the bolts you removed and reconnect all electrical connectors. Be careful not to wedge the ignition coil connectors between the ignition coils and the engine head, if you haven't yet connected them to the new coils.

Other comments:
The electrical / magnetic "head" of the ignition coils is completely sealed in plastic so you won't be able to open it and find the problem. Inside the "tube" part is a ~1.8kOhm ceramic resistor and a spring. The problem with the ignition coils is possibly the oxidation of the spring and its two electrical connections to the "head" and the spark plug. You are unlikely to be able to fix a coil pack yourself, so just buy 4 new ones for ~ $200. No-name variants are available for less money but seem to have a short lifespan, according to some negative Amazon reviews.

Links to Amazon parts are below.





Link to dielectric-grease usage on spark plugs:

I hope these instructions are of use to someone. Check out the Amazon customer reviews of the parts: there are many people with similar problems that were solved by replacing the ignition coils.

 

Speaking of valve jobs, I should probably do mine soon 😩