Engine Shudder

Ok I was with a buddy of mine yesturday and he has a 14 year old accord. Its a 5 speed and im pritty sure its got the 4 for the engine.
He shut the car off yesturday and even then it was the only way I can really explain it is that the emginme was still sort of running but really harshly "made the whole car kind of shudder" and it finally stopped after a few seconds. Anyone have some thtoughts as to what would cause this? Also when it idles its like around 750-800 rpm "its a 5 speed".
My guess is maybe the timeing is off??
But don't really know anything about engines so any input would be greatfully apreshiated.
Thanks.

if it still putters after you turn off the car, its the valves. after a while alot of gunk builds up on the valves, and what happens is that all that gunk is heated by all hte combusting in the engine, so when you turn off the car, that gunk is still super heated so it will ignite any gas thats in there. so you get combustion even though the car is turned off, and thats your car sputtering after you turn it off

Thanks,
What can 1 do to remady the problem. I pritty much know what parts are but as to how to fix them im totally clueless.

yes ck the timing first, but the idle sounds right at 800,
if you think it might be the valves as this guy sugjested. they have this really cool new tool that cleans the gunk off the valves without taking the engine apart.
call around and ask for a speed or tune shop that has the right tool it will prob cost 100 or so but well worth it.
also bad/cheap gas can cause that sometimes.