Hello all,
​ I have a '98 XLT with a 3.0 V6, and recently had power issues. Plugs, wires, and coil are fairly new, and I just punched out the cat yesterday. I'm certain the cat was clogged, causing my problem, but I still have a misfire in Cylinder 5. Could the back pressure from the clogged cat cause any problems internally? Any feedback would be much appreciated.

Bill

 

A clogged cat normally causes obviously a lack of power.

Driving a vehicle for long periods that is running bad and sending too much unburnt fuel could clog the cat over time.

Higher than normal exhaust temperatures from this condition could cause more problems like a burnt exhaust valve.

I would start with a compression test on all the cylinders.

Fairly new plugs does not mean much , one or more could have been damaged during the install the wrong type of plug could have been used or you could have installed one or more plugs that were handled to rough and damaged even before you got them.

A injector not properly providing the right amount fuel to the cylinder could cause a problem.

As mentioned I would start with a compression test, while doing the test inspect each plug and wire. If they all still look good measure the resistance of each plug and wire.

If the above somehow test good then do a fuel pressure test make sure it has good pressure and that it holds the pressure with the engine off.

Let us know what you find and we can advise you from there.