[webber]

Today putting my lights on I noticed the engine went from 1200 rpm to around 1700 rpm when idleing how does the revs
change by switching lights on and off?Sounds weird I know but that's what its doing have no idea what it is,battery is new.

Any advice appreciated cheers

[atari4x4]

voodoo magic



carby has an idle up solenoid to account for the extra load put on the motor by the alternator.

[abclarke]

What cars that? I hope an idle that high isnt normal on a sierra... (otherwise mines out the piss!)

[Bugsta]

Yes, it does sound a bit odd. In short, when you switch on a power user such as lights, it draws current from the battery, the voltage drops and the regulator on the alternator detects this, and makes the alternator supply more current to charge the battery and replace what is being used. This puts load on the alternator, and hence the engine. The engine management (if it has any. Not sure how this works with a pre ECU car) detects the load and increases the revs to compensate. Perhaps not 100% accurate but its my understanding of it.

It should not however, go all the way up to 1700 RPM. It suggests to me that *maybe* the battery voltages are not right. Can you measure and post the battery voltage at stand still, then engine running without, then with lights on.

What lights are we talking about - just stock, or high powered spots?

[webber]

Cheers bugsta I don't have any voltage measuring equipment haha sorry getting onto it soon.

I have small narva spotties but they are not hooked up.
I will let you know when i get it sorted.

Thanks for the reply mate

[Bugsta]

Hey what year is your Zook and does it have engine management?

[Reubs]

atari4x4 wrote:

voodoo magic
carby has an idle up solenoid to account for the extra load put on the motor by the alternator.

Webber, judging by your previous posts, I assume you have a Sierra?

If that is the case then adjust your idle-up solenoid as Mr Atari suggested. Easy to spot - look for a linkage on the front of the carby that moves when you turn the headlights on and off. Adjust the screw stops to a more acceptable level. I have mine set about 1200RPM (although not everyone will prefer that setting).

Depending on model of Sierra, your a/c, heater fan and headlights all increase idle speed. Some people adjust their idle up to act as a crude hand throttle.

[Bugsta]

Ahh interesting. Yeah thats more likely it

[webber]

Reubs mine is also set to 1200rpm idle so really I'm getting worried over nothing I am happy with my idle rpm.
Its the first time I've noticed this sorry just wanted to confirm with you guys if there was a serious problem
Obviously not so that's good news!!

Thanks for the help will post some picks of it when I can work it out etc in my rigs section

[sogone]

Your warm idle should be 800-900rpm. I think that's what the bonnet thing says. In regards to the 1200rpm he is talking about the idle up solenoid on the front of your carbie. Turn your lights on. This will turn the idle up solenoid on. You can adjust this by turning the screw until the idle drops. Set it at about 1200rpm as suggested. The FSM would have the factory spec set rpm.

[webber]

OK then I will have a go at it tom I guess it will save fuel turning it down a bit
Cheers

[sogone]

I'll take a pic when I get home of what needs to be changed. It's a bolt from memory not a screw.

[webber]

Yeh a pic would be sweet thanks mate really enjoying my Suzy atm.Not enjoying the stock engine
But its in good nick and goes well just a little gutless.Just need new exhaust bit more flow and maybe
Carb later but that's it want to keep it simple..
Being driving those AT3 discover cooper tyres its being pissing rain and they feel nice really grippy