It isn't causing the problem, so, solve that first, then start going after other stuff that really should be done. Or, you can just do it now.... Doesn't really matter. NTK or Denso sensor though, don't bother with Bosch, our trucks tend to not like them.

 

OK. Going to look at cap, rotor and get coil tested today. Probably should have done that when I put new plugs and wires in her a couple months ago. Any suggestions on a coil if bad?

 

Have you seen the spark plug wire TSB?

 

Cap, rotor and PCV valve replaced. Idled real smooth and drive down the road. When it warmed up it started idling rough and shimmying at 45 mph. Could it be the CAT? I looked at TSB on spark plug wires and they are all routed accordingly. Thanks for the input. Any other ideas?

 

Try the O2 sensor trick again.

Does the shimmy get better/worse if you turn off O/D?

have you fixed your plenum???

 

I did turn overdrive off and the problem didn't go away. I have done nothing with the plenum. I'm not sure if previous owner did or not. I am hearing a knock that sounds like it's coming from the lower end when it's warmed up.

 

check for pending codes.