I've been recently having a weird rough idle upon both doing a cold start and a start when the engine was only recently shut off. It's only a slight one, however, and it goes away after 5-10 seconds usually. It's also been happening (rarely) while idling at stop lights, for example.

I took it to an auto store where they scanned for codes and nothing came up. No indicator lights are on, either, so I'm at a complete loss. I had a maintenance inspection run on the car only a few days prior to when it started and they said everything came up fine. The car has around 106,000 miles on it.

Any ideas? I read that many people are having somewhat similar issues and have found success by replacing coil packs and adjusting valves. Hopefully this is all I need; the last time I ran into this rough idle issue, my 2001 Nissan Sentra had a blown head gasket...

Thank you all!

 

I had the exact same issue around 94-103k miles. Do the valves first, they're due anyway. That should solve it.

Now my car's around 150k miles and it's starting again. It needs periodic valve adjustments. I think Honda's recommendation was @ 100k miles and every 30k after that. Earlier if there's noise or symptoms.

 

Let your engine run for at least fifteen minutes, then shut it off. Take off the oil cap and look for foam or bubbles on the inside of the cap. If it's all good, check the gasket seal around the engine head and block. If there are no leaks or cracks in the gasket, you're good to go on that.

Definitely get the valve adjustment. If the clearances are off, in a cold start the tapping can be quite loud and cause a rough sounding idle, but it levels out as the engine warms and oil is pressurized in the engine. You'll want to do the adjustment first before paying for new coil packs, I can't imagine you'd need new packs at that mileage but if the valve adjustment doesn't work, ask your mechanic to check the packs to make sure they don't need replacing.

Worse comes to worse, it may be an idle air control valve which I had a problem with in a Honda Civic, it causes a rough idle at startup but smooths after warming up.

If your mechanic is any good, he should be able to figure it out pretty simply. A rough idle isn't a hard diagnosis. Good luck!

 

I gotta agree with Dr. Doom and Christian. I had been noticing pretty much the same symptoms you are describing. I bought a used fit with 110k miles on it and figured the previous owner never got around to that valve adjustment. I did the adjustment over the weekend and immediately noticed the rough idle, along with a few other concerns, were no longer there. It turned out my exhaust valves were craaaaazy tight.

 

There is NO idle air control valve on Fit! Throttle plate does it all. Rough idle at start (like running on 3 cylinders) most likely caused by ignition misfire

 

I'm having the same idling issue on cold starts once it warms up seems better but my situation add alittle more headache. Cel came on misfire cylinder 3. I changed all 4 coil packs and spark plugs with the recommended brands. Reset the cel 2 days later cel returned, same code for cylinder 3 and the cold start idle still bad.