litte bit of a rough idle when under elec. load

[inthar]

I'm still chasing down my poor mpg issue. I noticed that when I'm at idle and i flip the heat on the engine doesn't idle as smooth, little bit of vibrating in the steering wheel when I'm at a light. It isn't horrible but definitely noticeable. Any thoughts?Thanks.

[llamavan]

When you say "flip on the heat", do you mean moving the temp control from cold to hot, or turning on the blower?

Gwen

[inthar]

the blower motor. It also seems to happen when I turn on the headlights.Thanks

[Burntboot]

Anytime you induce an electrical load on the system the alternator will start cranking out some juice, putting more load on the engine.
Not at all uncommon for a "high draw" system (think headlights, heater, rear defroster) to cause the idle to come down a couple of hundred RPM.

[llamavan]

What he said. :whs:

How old is your battery? IME, an RPM drop in conjunction with blower motor and/or headlights (or a noticeable drop in headlight brightness when the engine drops to idle) can be a tip-off that the alternator is already busy trying to charge a dodgy battery (or charge via dodgy connections). A constantly-busy alternator is no good for mpg.

Gwen