Hey just doing a tune up on my old f150 its a 1990 with 351w e4od.
Im ordering the parts online. Cap, rotor and plugs. Question is should i order new wires or is it worth doing a resistance check on them?
They dont look cracked but not sure how old they are.

 

It couldn't hurt

 

Change your wires. I had 2 dead wires within a year from the zone. Better if you can get motorcraft wires. My opinion

 

Ford Racing wires aren't that expensive and even better quality then motorcraft

 

Suggest unless you have access to an unlimited amount of money - first check the resistance, put the parts you already ordered in, then consider changing the wires if the tune-up still seems lacking.

An additional suggestion is to look under the hood in the dark to see whether there is any arcing off the wires, indicating a problem with the wire insulation which a resistance check may not pick up.

As others have indicated - if you do change the wires, don't go cheap. I have also had 'disappointments' with the zone...