Idle drop

[stonemaster]

idles fine, lights on idle drops to about 600 , bad batt, alt ????/

[FestYboy]

nope, that's normal. loading the alt will pull the engine down. as long as idle remains steady, you're good.

[georgeb]

Turn everything on, including a/c. If it idles it's okay.

[stonemaster]

I never had a vehicle that was OK idling at 600 rpm ????/

[georgeb]

Turn it up some.

[Charlie1717]

nope, that's normal. loading the alt will pull the engine down. as long as idle remains steady, you're good.

What if it isn't steady. Up down up down rpms

[stonemaster]

Ok let me try this again, when the lights are not on it idles fine,(around 1100 rpm) when I turn the lights on it drops to about 550 to 600 rpm and u know that aint good, and thats supposed to be normal ????

[bravekozak]

Ypu should only require an idle up if the A/C compressor clutch is engaged or turning the steering wheel with power steering. Those two things will place a temporary drag on the belts and thus on the crankshaft. Any load on the alternator, over and above what it is rated for will result in the battery discharging to make up the shortfall. The drag on the alternator belt is constant. It should not have any affect the idle speed. Can anyone else correct me if I am wrong?

[Bert]

I have the same problem with one of my cars; low idle with lights and heater on etc, but it's been like that ever since I got it 2 years ago so I've stopped worrying about it.

[Movin]

mine is efi 90 5sp and has very little drop.
Are there any wiring mods or unhooked wires?

[runner406]

Can u actually adjust the idle speed without issues on these cars ? I saw the screw under the throttle lever today but i was under the info that idle should not be adjusted on efi cars ????

[georgeb]

Don't mess with that one. Adjust the one under the black rubber plug. You're supposed to ground the single test plug during the operation.

[runner406]

Can you take a picture of this one under the cap ?? I dont see a blk cap on my ride anywhere lol

[georgeb]

The cap might be missing. It's just right of the intake tube on top of the manifold. It's a large screw in a recess. Turn left to increase.

[angrygocart]

The rpm dropping in half by turning on the headlights is not normal. My 1990 fi Festy didn't have any noticable idle drop while using the headlights or radio. My 1988 carb Festy drops a couple hundred rpm with the A/C on. 1100 rpm idle is about right for cold idle but a little high for normal warm idle. I don't know what could be wrong, I would guess the alternater is putting exessive load on the engine when the headlights are on. You could goto a local parts store that would test your alternator for free.