i got a 1992* honda accord ex, back in the winter my accord started to have a surge in the idle while it was in gear or not, btw its a manual transmission, when the idle gets down to 1000 rpms it will jolt back up to 2500 rpms then fall back down and just keep doing it over and over.
however when i start the engine cold it doesn't have this problem, but as i start to drive it the problem will arise.
the most recent work ive done on it is just putting a new fuel filter. and put a new clutch pedal in.
any ideas?

 

First thing you do is check the coolant level.....if low you will need to "purge" the air from the system, there is a bleeder on the t-stat housing.

 

Yes, having air in the coolant system can cause this.

Vaccum leak would be my guess. I would check for that too. IACV's and FITV's malfunctioning are also a type of vaccum leak.

 

Likely the fitv needs to be tightened down.