keltong

Can anyone give me some guidance on my 2002 mustang coupe 6 cyl. Rough Idling at lights or in park... Sounds like its my exhaust when I hit the gas... Has gotten worse, cats are rattling... Runs better and quieter on highway versus on local streets... But when its cool or rainy, runs much more smoother as if no problems... Any suggestions ???

g96v6-250k

if you have a bad gas mileage no matter how you drive, sounds to me like busted up cats/res or maybe injector problems or way too much ethenol. are you sure the cats are rattling? check for heatshield noise or the id plates under the heat shields, they can come loose and make alot of noise. if the shield are pushed in on the cats/resonators that can make noise also. does the engine vibrate alot more than it did in the past? maybe clogged cats from rich fuel trims. these things can be a biatch. good luck

claudermilk

Start with the easy stuff. Plug, wires, air filter.

keltong

Thanks for the guidance claudermilk. Changed the plugs, wires, plugs, and cleaned the cold air intake... Think I should replace the Coil next? She still handles smooth and fast, just loud at idle or acceleration...

keltong

Good Gas Mileage... Cleaned the fuel injectors. Yes engine vibrating slightly more when coming off the clutch than when I first got her not to long ago. Think you might be right about it just being the heat shields vs. cats. How can I pinpoint easily? If clogged, should I just pay to clean or do myself if possible; or should i just replace the whole cat component?

g96v6-250k

good mileage like 25-30mpg without racing around? did you get injectors ultra-sonic cleaned and flow measured, if not theres no guarantee they work right.
if cats are clogged its possible going wot for a long time might open them up but thats risky with these faster cars as you can be at 120 in no time. did you ever smell sulfur-rotten eggs smell from the exhaust when you get aggressive on the throttle. im pretty certain the rain or cold dense air making it smoother means you are having a rich-trim and eventually plugging cats if you try to stretch out your fuel mileage. my cars love to breath fog and cold air, it vibrates less and has more power with less throttle. i think this is because it runs too rich. maybe have eec/ecu data looked at "fuel trims and engine temps.