Found out that RockAuto sold fake iridium plugs a while ago and I need to get mine changed out just in case I have those in my engine, which happens to be a 3.6L and has 133K miles and has some very minor stumbling. I am considering changing the factory ignition coils because of the mileage and the lifters because the intake doesn't get taken off too often and they are fairly cheap. My question is do you guys think replacing the lifters, even though they are inexpensive, is a waste of money, or is it even safe to the engine? As in, will the cam tolerate new lifters? The engine only gets full synthetic, changed every 3k-3.5k, city driving.

 

Rock Auto had sold some counterfeit NGK plugs after receiving a bad order and that was about 3 or 4 years ago as soon they realized they weren't original NGK they stop shipping them. If you have some counterfeit NGK contact them and take a picture of the plug and they will replace them for free with original NGK plugs plus a discount for your next order. Ignition coils are pretty well made and rugged as long as you keep up with maintenance on your plugs right gap and change interval they should last for quite a long time. Lifters if they're not ticking I wouldn't bother if you're using a good quality brand oil and proper change interval I think it's a waste or money.

 

The lifters on these engines are not like typical, flat bottom or roller type lifters that ride directly against the cam lobes. Although they do provide a small amount of lift to take up slack, they’re actually more like a pivot point for the rocker arm, with the rocker arm roller being what rides on the cam lobe. In theory you could replace just the lifters without worry of damaging the cam.

That said, unless you’re having valve train problems related to the lifters, there’s no reason to replace them.

If you suspect problems with the lifters, I’d suggest just starting with an inspection. Pull the valve covers and inspect the lifters, rockers and cams for damage or excessive wear. With all the spark plugs out, the engine can be rotated by hand easily using the crank pulley bolt (clockwise only). Rotate until the lobe is opposite the lifter when pressure is at its lowest - you won’t be able to see much, but you can check for excess play.