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Dikt8r

Hi there, asking this question on my friend's behalf.

she has a 2001 honda Fit done 130k. drives really well no issues but lately has had rough idle at cold start.

RPM stays at about 1200 but when you put your gear into D and in hold position - it keeps dropping to below 500rpm appears to stop but picks up again to 1200ish rpm and keeps doing that till warm.

Last weekend this car was driven to Taupo and after that trip it has been behaving ok but might come back. Wondering what the reason could be? Throttle body? Carbon deposition? plugs or coils? What would be the best way to fix it?

Many thanks

ABayliss

It's impossible to say without doing any diagnosis and the reality is that any of your suggestions could be possible causes. Obviously, make sure basic things such as spark plugs (which you've mentioned), air filter and air intake system are in good order. Also, the valve clearances are adjustable on this model.
If it's only occuring when cold, it sounds possible that it's running too lean by sucking in air when the mixture needs to be rich from cold.
Some other suggestions could be the crankcase breather valve, EGR valve or even the crank angle sensor. Unfortunately, the "guess" list goes on and on, so I'd suggest having a mechanic take a look.