I have a 1999 Mustang
35th aniversary v6. It has 138000 miles. Just three weeks ago, I had the same problem you had.
I bought a code reader and it said 6th cylinder misfire. I had purchased the car only one week before.
The gas was low when I bought it, so I filled up the first full tank with premium gas. I thought that would help the engine. Wrong, it actually caused the car to run very rough. I put injection cleaner in the tank, no improvement.
Next, I took it to the mechanic and had all plugs replaced, all plug wires replaced.
I had the oil flushed and replaced with synthetic oil.
I put another tank of premium gas in and the car continued to run rough even though the 6th cylinder error code was gone. It was not as rough, but still noticeable.
I had the fuel filter replaced and it was full of brown rust particles. Obviously the tank rust had plugged the fuel filter. Either the top of the tank was rusted, or, there was a collection of debris in the bottom of the tank, since I let it run completely out of gas and filled totally full.
Next tank of gas, I put regular gas in the tank with injection cleaner. It is now running really good. I guess the computer was smarter than I was, it just didn't like the higher octane.
hope some of this helps.
Originally Posted by tvsr
So i have a 99' v6 mustang with about 130000miles on it. a few months ago it started giving me some problems, put the computer and said i got a 6th cylinder misfire. Ok so i put new spark plugs, new MSD conductor spark plug wires, transmission and oil change, new fuel filter, injectors cleaned, I even put a new intake and masterflow muffler. while the car symtoms ( shaking, hesitation, lack of power, poor acceleration) have kind have gone away i no sooner or later running on 5 cylinders is going to ruin my car. the engine was reconstructed at 100000 miles before i ever got the car, i thought that it might be the problem but it happened months after i bought it. No vaccumm leak, i've tried everything i can think of and the mechanics are hella robbing my money and never fix it right. Any suggestions or solutions? Should I open the engine and check it out for myself? thanks for the help and time