1991 Honda Accord Engine revs up and down when warming up

Hi there,

Ask your mechanic to inspect for vacuum leaks, and check the idle air by pass system for faults. Start here.

Mark (mhpautos)

Without taking it to a mechanic or first, check the coolant level in the overflow and radiator. Make sure it is full of coolant. When the coolant gets low and air gets in the system this allows air to set on sensors and causes faulty readings and confuses the computer causing it to over compensate with more fuel then less fuel. Purge the system of air. Then as you have been told check the system for pressure and the ability to maintain the proper pressure the system requires.