Being a new owner of an older truck, I was thinking of doing a tune up first and then go from there.
oil and oil filter and air filter already done.
The issue is the idle going low and then high by itself
any ideas
Thank you all
smitty

That sounds like a leak in a vacuum line or worse it could be a leak in the intake manifold. Check all the vacuum lines and make sure nothing is cracked. Once that is sorted if it still idles oddly what I do is this: get starting fluid and spray small amounts around the intake manifold while it’s running, if it idles up then there is a bad gasket seal there.