My 2001 Tahoe has a funky idle most of the time but not always. When I have
the
problem, the RPM drops to almost nothing and then goes back up to about 1000
RPM once every second or so. It's always the same, it acts as if  the normal
RPM was near zero but I was stepped on the gas every second to keep it from
stalling (I'm not). It has stalled on me a few times while this was going
on. It doesn't do this if the A/C is off. Since it's got a regular rhythm
and doesn't happen when the A/C is off, my theory is it's not something like
a dirty carb or bad fuel. Maybe something related to an electrical problem
and the A/C uses too much power or maybe a bad battery. Is there something
that somebody with only simple car maintenance skills could check before I
take it to a mechanic? That would be a lot of money for me.
Thank you.