I have an hidromatic 4 speed with overdrive Honda Fit second gen with a 1.4 liter petrol engine. When I'm cruising around 100km/h with very very light throttle, and I very gently press the accelerator pedal over a hill, the car "hiccups" like it wants to downshift but it doesnt, and its really specific. Sometimes very rarely it happens when Im in drive with the AC waiting for a traffic light to open, it just "hiccups". It has beeing like that for over 2 years, I change the fluid and filters every 40.000kms and the car has over 180.000kms. Other than that it shifts and drives absolutely fine. The revs doesnt seem fo be affected when it happens, or its just too fast for the panel to show.

 

Would you describe these hiccups as a lag between pressing the throttle and the car responding?
have you ever overheated it?
past two cars i worked on had that lag symptom and it turned out to be the timing chain guide/tensioner. Plastic got brittle on the guide and started to flake off. This allowed for slack in said chain. So, the engines turning, but theres slack in the chain. That starts a very mild whipping motion when you go from no throttle to... some. Keeps whipping for years, breaking off more and more of the guide til the plastics gone, and stretchin/stressin that chain. Eventually it gives. Didnt catch it til it was too late. Bent valves.

Now, I dont mean to put bad thoughts in yer head. do *you* think that might be whats up?

 

I don't think it might be it...I can't describe it as lag, it's more like really a very mild hiccup...it's like you're going over a small bump on the road. The car drives and runs absolutely fantastic, I did a compression test at 166.000kms and the engine is absolutely perfect. Im thinking it might not be a transmission issue, but maybe bad injectors or a coil pack going. I noticed when I'm using regular gas, it tends to happen more, when in on premium it doesn't happen. And have in mind, here in my country premium gas is just regular gas with addictives.

 

It may be fuel quality then, instead of a mechanical/electrical failure. To test that theory all you'd need do is pull and inspect all four spark plugs. Annoying as hell, but worth it. You're welcome to post up some pictures of them too! Oh and be sure to keep them matched to their respective cylinders for diagnostic purposes, of course.
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I also noticed when the AC compressor kicks in, it really mess up with the idle when in D pressing on the breakes. The car just "jumps" when the AC compressor kicks in, when i'm in the highway, the AC also makes the car act up a lot worse, with the hiccups happening more frequently. I think it might be the culprit. I took out the spark plugs and they look fine, I dont see any irregular burn.

 

Glad to hear the plugs are showing right. If we're moving on to thinking its the compressor, theres some more stuff to test! I imagine the A/C compressor clutch could be a possibility. Perhaps when it kicks on? We could get some ideas if you could have a friend sit in the car and turn the ac on while you watch and listen to the compressor. If i recall correctly its on the vehicle front right side at the bottom. Kinda standard location. Try it with the car warmed up, cold, and have em press on the throttle while you watch that pulley wheel. I've got the service manual for the car so I'll check it out a little later and see what info I can pass on in regards to the system

 

Theres the troubleshooting procedures for the compressor clutch itself. I've got the whole book, so let me know if you want to pursue a specific direction from here.

 

2nd gen 5 speed automatics (4 plus overdrive?), at least in the US market (I think this would be the same for Brazil) have torque-converter lockup in all gears.

It feels like something is disengaging when enough throttle is applied before it actually shifts. You'll also notice a change in RPM. This might be the "hiccup" you feel.

The torque-converter takes the place of a clutch in these cars and allows the engine to turn at a different RPM than the main-shaft of the transmission. This is necessary to keep the engine from stalling when you stop, and also allows variable torque to get the car moving. This mechanism uses fluid through 2 sets of vanes (turbines). It's necessary but wastes energy at constant speeds. The lockup creates a solid connection between the engine and transmission making it more efficient.

All automatic transmissions (not CVTs) since the 1980s have torque-converter lockup, but in older cars this mechanism only engaged in the highest gear at highway speeds.

If your transmission had a major issue, one or more indicator lights would alert you to a problem.

 

First off, big thanks to the gent above, solid info there.
Brought somethin else to mind. This likely wont help much, but I and my dealer found it interesting. My 12 fit had trouble with it's A/C system a year or two back (long forgotten.) The only symptom was the air not cooling despite the charge being good and the system untampered with. Followed honda's troubleshooting procedures and found no faults til checking ohms on the field coil. Came in at 4 instead of the recommended 3.something shown in the post above, last image. I popped the bad boy out n found it had a little hole melted into its face.
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Stopped troubleshooting and got a new coil, which also ohmed in at 4, so that didn't fix it. A rat chewed through a wire hidden by the front right headlight. At any rate, if you or anyone find yourself testing the coil while going through the above procedure, expect mildly out of spec ohms from P/N 6LJ25L, and feel free to continue troubleshooting beyond it.

Here's the aforementioned coil, now a keepsake.
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to the OP, be sure to let us know if you get this solved!