Asked in Toyota Echo
Toyota Echo

What causes rough idle when air condition compressor turns on on a 2000 Toyota Echo?

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Wiki User
04/28/2010

When was the last time you had a tune up? When the a/c pump is engaged it causes parasitic loss of horse power and rpm. The computer sees this loss and adjusts accordingly. From what you state, the vehicle rpm is dropping to low causing the vehicle to idle roughly. Give the vehicle a tune up and this should fix the problem.