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08 Honda Civic running rough on startup

I have a 2008 Honda Civic with 65K miles. It’s started idling rough and vibrating just on startup when it’s been sitting overnight. This continues until I start driving up the road at which time it stops. I ran a fuel cleaner through it and changed the air filter, which was slightly dirty but not too bad. No effect. Then I took it to my Honda mechanic and he said there was nothing wrong with it. Any ideas?

Did you buy the car new or know its operating and maintenance history? Auto trans? Rough idle in P or D? I’d guess sparkplugs, but I think you have 100K iridiums in it. Edit: Not so easy to change.

I bought it new and it’s never had any issues whatsoever. Automatic transmission. It’s idling rough when I start it (in P obviously) and put it in reverse to back out of my driveway. Once I put it in drive and gun it up the road it goes away.

I did mention sparkplugs to the mechanic but he said the plugs I had wouldn’t need changing until a tuneup at 105K.

Tomorrow morning, start it 20 minutes early and let it idle. See if and when the shake goes away or the check engine light goes on.