Yet another strange idling problem
 

My 85 GS has a dual personality when it comes it idling. At night when my headlights are on and I come to a stop it idles nicely at around 800rpm. However, during the day when my lights aren't on and I come to a stop it idles at around 1200rpm. If I put a little load on the engine by slipping the clutch it'll drop down to 800. Does anyone have any idea what could be causing this? TIA

Adjust the idle? (a little lower, check the mixture)
Check the emissions crap? (Maybe the ACV)

Could be a few things...

what's the ACV?

Sorry, been on the board to long....

I had this happen a little with my GSL-SE.
I fixed my ACV (Air control valve). If you still have your emissions stuff on, then it is located below on the exhaust side (passenger) just above the exhaust manifold.

Also you might wanna check that you guage isn't sticking. Mine is occasionally doing that now. Most of the time it's bang on and then other times if seems to idle about 200-500rpm high, but it's just the guage sticking cuz when I turn it off it sits at about 300 rpm. A quick nudge on the gauge panel and voila, instant fix...

Good Luck..

on the thing of Tach stick, anyone had them freeze over night, or anything when it gets really cold out??

OK itz an 85 GS with a carb.. go through and make sure that the throttle cable is not under pressure at any points...should be stickin out in the air more or less. When your in the car and it seems to idle up like u mentioned, put your foot under the gas peddle and pull back on it a lil. You will notice it will go back down where you like. But when you hit the gas again it will idle back at 1200. There is resistance on the cable. After you have checked to make sure it is free from kinkz. Look up the gas pedal to where the cable leads out of the car. Spray a lil WD-40 or a lil of some other type of lubercant there... and a lil on the end that connects to the card, try to feed it up in the line if possible. There is also a linkage on the passengerside of the carb, it seems that most people want to flip this down but it should be held in place. I will try to explain this the best I can. Stand on the passenger side of the car and look at the carb. You will see something that looks like a small folk lift on the bottom left of the carb right behind the throttle leakage from the driver side, and right below it you will see a piece with two arms that looks like it would be held there. get a pair of neddle nose plyers and pull it up onto the folk left. You will notice your Gas pedal is a lil more teguss(sensative)seemz to tighten all the linkage to the the trottle. Hope that made since. Hope this helpz.

Mike

Well it seems that the throttle does not in fact shut all the way. This is part of the problem. The cable is fine but the dash pot seemed to be adjusted to close so I backed it out a few turns. This has almost fixed the problem. Now about 50% of the time the car will settle down to an 800 rpm idle.

There is always a loud vacuum sound coming from the Shutter Solenoid Valve opening in the air cleaner when the engine is idling high. I wonder if this is the source of my problem. When it's idling high I can always make it slow down by breaking the vacuum going into this.

Any additional thoughts on this?

Thanks for all your help!

PROPLEM SOLVED! :D

I'm posting this for the benefit of others that may have the same issue. Make sure your carb is clean then use WD-40, WD-40, WD-40, WD-40. Use lots of it on all the carb linkages. I also adjusted the idle mixture and throttle adjustment per the Mazda factory manual.

She runs as good as new now!

Me happy! :)