P0442 Ford - taurus 1999 3.0 DOHC

Question

idle goes up and down when A/C or defrosters on as well

Answer 1

P0442 Evap control system leak detected (small)

This code is not going to cause the idle to fluctuate.When the idle goes up and down it usually caused by a vacuum leak or unmeter air that gets past the MAF (Mass air flow) this can be from a vacuum hose from the PCV valve or any rupture or disconnected vacuum lines allowing false air to enter the engine system. P0442 are mostly cause by fuel cap seal that are worn or not properly sealing