Honda Car Forum

A friend has an 86 Accord LX automatic. He says on level ground and
at constant speed, the tach fluctuates back and forth by about 200
rpm.

Well, I think that has to be the transmission going into and out of
lockup. But what would cause it to go back and forth like that?

After a past change of coolant, my 94 wouldn't go into lockup at
all. But when they finally got all the air out, it worked fine.
Could it be something like that? I asked him, and he said if
anything his engine temp runs a bit high.

Any suggestions to things to check?