Hey Guys,

I recently changed the spark plugs and wires on my '94 F150 4.9 L E4OD. I now notice that the truck seems to idle a little rough and, to be honest, it seems as though it's missing. I can notice the miss even when driving the truck and I am quite sure that there is a loss of power, as well.

When I replaced the wires, I did it one by one. In other words, I pulled one old wire off of the plug and the distributor and replaced it with a new one before going on to the next wire. Therefore, I am pretty sure that I didn't misplace any of the wires while installing them. If I did, I am absolutely baffled as to how it could have happened.

I am wondering if any of the following factors could be the cause of the symptoms:

1. Not replacing cap and rotor when replacing plugs and wires.

2. Over gapping of new spark plugs.

3. Poor quality wires.

4. A vaccum leak.

I mention the vaccum leak because after I shut the engine off, I can hear a hissing that lasts for a good 15 seconds.

I am at a loss. I bought this truck very recently and it ran GREAT. I thought I was doing the truck some good by replacing the plugs and wires, but it seems that I have done no good at all.

Any help or advice would be most appreciated.

Thanks guys,
Garry Baker