Ok, I have a '99 f150 with 4.6. It runs great, idles fine. But under moderate to heavy acceleration , it will hit a weak spot in the power band. But once it gets past the week spot it will continue to speed up like it should. Any tips or suggestions? Thanks.

 

Dead spot? Do you mean like a misfire?

Have you checked for any pending codes?

 

No, no misfire, when it hits a certain rpm its looses power and when it gets past that point it gets power back.

 

...and no sel.

 

"Service engine soon"

 

Having any exhaust problems, like clogged cats or anything? My truck kicks in like it has V-Tec, I chalk it up to my factory cats being clogged.

 

Maybe clogged cats...how do I check?

 

A muffler shop like Midas can check it for you. I had one checked several years ago and they drilled a hole in the exhaust in front of the cat and used the hole to check the pressure while revving the engine. Mine was okay.

 

In my case, I could hear the internal workings of the driver side (by the door/fender area) cat rattling around a little. After starting it up on a cool morning, I got under it and could see water dripping out of it (it being the catalytic converter), which meant it had already rusted a small hole in itself from trapping that moisture in.

 

Well, the cats don't appear to be rusted, not dripping water, no rattling sounds and no funny smelling exhaust.