Joyrider564

Well, my friends 99 Mustang started to develop a misfire. He took it to jiffy lube, and they replaced the fuel filter. Also, car has a little exhaust leak from the passenger side header to the off road x pipe. It started misfiring horribly, hardly can get out of it's own way. So we took it to autozone, and they said cylinder misfire on 1 and 5. From my experience, I figured it was a coil pack, so, we replaced them, and the spark plugs. Unfortunately, this didn't solve our problem. I tested the car to see if it was getting spark by pull the plug and the coil pack out of the cylinder, and turning it over (i also disconnected the injectors at the same time), and it appears to be getting a spark. my next step is to check the injectors as well.

I also cleaned out the mass air sensor, and the ol' battery disconnect and reconnect. But neither work. The car at idle sounds like it is loping like it has a cam, but unfortunately does not, and when I rev it with it standing still in neutral, it just won't go above 4k rpm. Any thoughts? The guy needs to drive to pittburgh in a couple of weeks, so needs to be fixed quickly. Thanks! I appreciate your help.

white07

Have you tried new plug wires? I know on my old 96 GT when my wires went bad my whole motor was shaking. Also check the holes where the plugs go for moisture b/c with the mod cars they get moisture down in them b/c the hole is on top.

01stalliongt

i had sort of the same prob about a month ago changed the fuel filter and had everything checked and it still done it but i put an octane booster in it then about 3 tanks later it just kinda quit doin it running good now just some input

jst854

The same thing happend to make a couple of weeks ago. I replaced the plugs and wires and that fixed it. Try disconnectingthe wires from the coil packs while the car is idling and see if it gets worse or stays the same, if it stays the same for any cylinders and you already replaced the coils and plugs you are gonna need new wires.

Joyrider564

99+ doesn't have spark plug wires, and I have taken harnesses off of each coil, and ignition isn't the problem...

I think they put in the fuel filter wrong, because the cylinders that are out are the 1 and 5, which is farthest from the gas tank/ fuel filter, so not getting enough fuel. I'm gonna have him take it back to jiffy lube to see if they can fix it.