Rough idle and loss of power and gas mileage

First thing, fix leaking exhaust, this can cause erratic idling...second thing, remove and clean IAC valve and MAF sensor..dry and replace, also try putting some SeaFoam in the petrol, engine oil and air intake, let sit for 10 minutes then go for 10-15 min drive...suggest you change engine oil shortly after driving about 5000kms, if the oil is old..

Did you get any codes on the misfire? If you did not, test ignition coils, test vacuum, test fuel injectors, verify correct plugs..That's right, anything from a fouled spark-plugs to burned cylinder head valves can cause a misfire. Whatever the root cause of the misfire, the bottom line is that one or more cylinders are not contributing to total engine power output. This leads to power loss, rough idle, unstable RPM and bad gas mileage...cheers

Fuel filter air cleaner filter plugged or need a tune up or air sensor in intake line put on computer will tell you right away if you want

if the car is loud/noisy there is a hole in the exhaust system and this will cause a rough idle because of a loss of back pressure and the vales will not open and close properly resulting in the rough idle it also will make the engine run hotter and this will cause your spark plug gaps to increase and the spark will be less than needed to ignite the fuel in the cylinder for proper combustion which will result in poor gas mileage and lack of power is the check engine light on?

I would first be sure that you have spark to that cyllinder. Pull the wire off and stick an extra spark plug in the wire. Lay it on the engine block somewhere and atart the car to see if it's sparking. If it is, you have a valve or cam problem. If it isn't check the plug, the wire, distributer, coil pack etc.

yea sounds like a belt or Chane but dose not jump going down the road much most of the time will do it when u start the car..

hi.
go to this link might help you get it sorted.
Honda Accord Rough idle right after starting Google Search

i would suggest doing a full tune up and engine flush, if this does not correct the problem then there is something else wrong and needs to be checked on a code machine

http://groups.yahoo.com/group/villagerquest/

I have changed plugs using the platinum plugs and the problem don't go away. These plugs can make a car run worse in some cases. I have found it best to use the OEM or a step above on 4 cylin and 6 cylin engines. The Plats work fine in 8 cylin engines. You could also have a bad plug wire. The plug wire could be jumping spark. At night, open the hood, start the car with lights off. Look around the plug wires for sparks jumping. If a wire is bad, the spark is leaving the wire and grounding itself to the nearest metal causing rough engine idle and misfire.

try having fuel injectors cleaned out those get clogged up and cause pinging rough idling loss of power and gas mileage good luck