[mustang34]

I have a 2000 V6 Stang...and I love the car. I bought it from a friend who had it stored for 3 years. I changed the spark plugs, wires, oil/filter, coolant, air filter, tranny fluid. For some odd reason while the car is cold she runs like a raped ape but when the car warms up she runs TERRIBLE. It runs so terrible that I can barely keep it running (the more gas I try to give her to keep her running the worse it gets). I knew when I got it had a 1/4 tank of old gas so I went and filled it up with the highest octane fuel (Im on my 2nd tank), added some booster and also a bottle of the best fuel cleaner there is "sold at Napa" and it still runs terrible. I let the car cool for 2-3 hours and again she runs awesome. Check engine light was on saying P0301, P0303 and P0411 but they have since been cleared when I changed plugs and wires. What could be causing this significant power loss? Any help or tips would be greatly appreciated and I will definitely try anything. I am stuck. Thanks

[2000stallion]

Did you take it to auto zone when it threw the code?

[mustang34]

Yeah they told me what the codes meant and is why it was necessary to change plugs and wires...which i was planning to do anyway. The sputtering and running terrible was happening before the plug/wire change and i thought it was the reason causing my problem. Then I drove home from my friends who lives 2 miles away and boom the problem happened again. UGGH I am so stumped! I have been over and over forums and calling friends. Thanks

[2000stallion]

Its not overheating is it? i dont know why it would run like shit when it got warmed up?

[9986paulk]

It sounds like some sort of closed loop issue...when it's cold it runs in open loop, without some of the input sensors. So maybe bad oxygen sensors/MAF?

[mustang34]

I don't know what MAF is or what it does other then what google told me. The car isn't overheating. Is there a way to test or rule out the MAF?

[v6kid]

It shouldn't be the MAF, even when the car is in open loop the MAF is still used. If it was bad it would also run like poo in open loop.

P0301- cyl 1 misfire----------------------------- effect
P0303- cyl 2 misfire----------------------------- effect
P0411- Secondary air injection incorrect flow----- possible cause

If the air injection flow was wrong it could cause the 02s to read bad and give the incorrect amount of fuel. 02s send info after warm up, not when cold... As a test disconnect your front 02 connectors, and see how it runs cold and how it runs warm with the 02s unhooked. Do not drive it like this.

[mustang34]

The cause of the misfires were holes in the spark plug wires and they were arcing across eachother and the manifold. When I changed the wires and codes went away including P0411. I will try disconnecting the the front 02's but its tough to tell because it idles ok