So my 85 fast idle is too high 1800 RPM'S and someone told me to lower it by turning the idle adjustment screw (which is the upper right screw) and I turned it 3 turns to get the fast idle down to 1200 but now it stalls when I stop. What next? If I were to play with the lower left screw would it mess up my emmisions?

 

when you say it idle's at 1800rpm is that when the engine is cold or at normal operating temp? The screw to the lower left is the fast idle control, whenever your lights/AC are on it controlls the idle. To adjust the base idle you have to unplug the harness connector to the idle up solenoid. Then once you adjust the base idle to 700-800rpm (note you have to do this when the engine is at normal operating temp with no load on it, like the lights/radio/AC), reconnect the harness. Your base idle should be correct now.

 

Note: If it's cold where you live and you have a problem with your thermostat, you may never get to a proper operating temp and you'll have a fast idle. Also if the small air bleed holes in the throttle body are clogged this will mess up the idle. A bad throttle position switch will also effect idle.

 

The fast idle problem is only when it is cold. It will start up and idle at 1800 rpm for about 3 min. I want it to idle at about 1200. It will idle properly at about 800 when it warms up. I think it is hard on the engine to run at 1800 when it is stone cold. Sometimes it makes a ticking sound for a while when it is cold. This is an engine with 250,000 miles.

 

Hmm if it idles perfectly when warm I don't think there is anything you can do about the cold idle. Most of the problems we have is when the car won't idle when its cold. Maybe you should switch to 5W30 oil, as for the ticking that could be the lifters. As long as it goes away once the engine warms up its fine.

 

Ticking sounds, after first starting, is due to lack of oil in the top end. If your oil filter doesn't have a back flow valve to prevent the oil from draing back into the pan you get the noise. Nissan filters have the valve (so do Purolators and most good ones, Frams do not).

 

I will stop using Frams and will start using 5-30 synthetic oil. I guess that I will just live with the 1800 start up revs. Thanks for all the good advice.