Hey guys -
New member here........i have a 1998 Mustang 4.6L converitable. I love it and have owned it for 8 years. I only drive it in the spring and summer. It has 220,000 miles on it. I am having trouble with power. I put some new plugs in it last year and it ran ok for a few months then went back to bogging down again as high speeds, and I would get like a spark knock sound as I was accelerating. The plugs I use are the Split Fire ones. I have read on some forums that its best to put the original Ford spark plugs in it. I don't know if this will work or if you all have tried this and found another spark plug that seems to work best..... let me know.

 

Split fire are crap, use the motor craft. How old are your wires? Are you still on the original fuel pump? Maybe its going weak. Are you getting any codes?

 

Yeah, OEM Motorcraft plugs are a great choice.

 

As they said split fire are garbage, however it is very possible your engine is detonating. With that kind of mileage it is likely you have a lot of carbon on your pistons which is causing hot spots and premature detonation.

 

. Thanks for the info. The wires were also replaced last yr. Yes I still have the same fuel pump, but I did get some codes and my mechanic said it came up on his computer as a bad purge valve in the gas tank...could that be the cause of the power loss??

 

. Thanks for the reply. Is there anything I can do to clean the pistons???

 

not unless you plan on taking your whole motor apart

 

Motorcraft plugs are the way to go. In fact I get Motorcraft for just about anything I replace (plugs, filters, etc).

 

Try a different set of plugs, maybe new wires and coils, a fuel filter, test your fuel pressure, and do a leak down test on the cylinders, thats a good place to start with something with mileage that high.

 

Bogging down at high speeds sound like an intermitent problem. besides, you said it ran fine for a while so i wouldnt blame the motor just yet. A loss of power like that can be caused by loss of fuel, spark or a bad maf. Auto or 5 speed? Some autos will cause bogging problems on their way out the door.