Rough running motor

[Schultzy]

Heya all,

Have been having some issues latley with the NA.....

When the car is warmed up and idling, the revs drop when i push the brakes or have headlights on.

For eg, if i sit at traffic lights, clutch in brakes and lights on, revs will drop and motor starts running quite rough like its struggling to turn over....then goes back to normal when i take my foot off the brake...the power windows also have the same effect too......would this be an alternator problem or something a little more major? I cant quite work it out as its only started happening recently. Feels like something is draining power badly

Cheers
Schultzy

[JBT]

It would be best to get it checked by an auto electrician. You may have some mystery short circuit happening there.

[Babalouie]

Sounds like an earth problem.

Check your terminals, and the earth strap from engine to chassis.

[fattima]

Is the idle set correctly in the first place?
My NA had a similar problem when I got it, the idle was not set correctly and the first time I used the lights the engine wanted to stall. See link about setting idle.
http://www.miata.net/garage/KnowYourCar/S7_Idle.html

If this already OK I would get an auto elec to check out.