How and when do you know if servicable parts like, spark plugs, and HT leads are due for renewal? Is there a hard and fast rule that people swear by or is it just a hunch you get that things need a good service.
I ask cause when I first got my car, 18 months ago now, I gave it quite a service, spark plugs, dissy cap, rotor arm, air filter, oil, oil filter, 10K boost. After a slight problem at the pod (where 0ddball and co came to the rescue) one of my saprk plugs had come loose and was blowing the HT lead off the plug, the lead rubber got slightly damaged. I had the plug out and the tip looked as it should, and I went on to get very good 1/4 mile times. So after 12,000 miles and 18 months of use, should I change plugs, even leads, or should I stick to the philosophy "if it ain't broke don't fix it"?
If there is no misfire, no obvious problems, leave as is. I think now and then that I should change mine. Not even sure what's in there and I have had the car 6 months. Still there are no signs of them failing.. so they stay for now.
I would change the spark plugs every 5 or 6000 miles, thats when the gap needs adjustment, and I wouldn't bother correcting the gap because correcting the gap on four spark plugs, you can always guarantee the gaps are slightly differenat, the difference can be minute, but it does make a difference and don't put them back dry, I always use copper grease, it stops the spark from waring out the thread in the engine block. With regards the HT leads, I would change them every 12 or 15000 miles, once a year.