I have a 1995 Jeep YJ with a 2.5 4-cycled engine. At idle it has a noisy lifter tapping. I am old so in the old days we used to get out the feeler gauges and adjust the valve clearance but now the job is done with a hydraulic lifter. If only one lifter is making noise is there an additive that can correct this? MOA additive has been suggested but thought you might have a better one. The engine does not use any oil between changes and is on synthetic with 187000 miles. It has a manual transmission and runs great. It is not not something I worry about but could it be time to put in new lifters?
I am old so in the old days we used to get out the feeler gauges and adjust the valve clearance but now the job is done with a hydraulic lifter.
Hydraulic lifters have been in use for decades. That Jeep 4-cylinder engine is based on the architecture of AMC's 232 six which debuted in 1964, and hydraulic lifters were employed well before that. (The first car engine to use hydraulic tappets was the 1930 Cadillac V16 and many engines used them by the 1950s.)
It is possible to adjust the preload on the lifters by using the appropriate length pushrods, but that's unlikely to be your problem unless you have one that is slightly bent:
https://www.youtube.com/watch?v=UlizCeJfsus
is there an additive that can correct this?
Not if the lifters are wearing out after 30 years and 187K miles. If just sticking due to carbon buildup you could try the ATS Carbon Clean product that Scotty recommends. There are various snake-oil type "fixes" you could try of course. (Unlike today's engines that old AMC mill is not too picky about what you put into it.) Some say that Marvel Mystery Oil can free up stuck lifters, but I've never tried that myself.
could it be time to put in new lifters?
Quite possibly, no way to tell from here.
It's also worth mentioning that an exhaust manifold leak can sound an awful lot like a valve tap, so you might want to check that.
@chucktobias a mechanics stethoscope would help with that
It is not not something I worry about but could it be time to put in new lifters?
If you intent to keep the vehicle, then it's something to think about . Replacing a camshaft is much worse.
