Won't Idle below 1000

Your last statement makes me think it'd be a carb issue. But I'm no mechanic either!

well I can barely get it under 1000. So should I set it to 10 at 1000? Where are the mixture screws and how do I know they are set to max vacuum? Turn left for max vacuum?

1000 degrees? Do you mean 10?

How come I read 6 degrees BDC on the valve cover, yet I should set it to 10? Which one?

WhiteLakeSkier wrote: It also idles in a way that makes it rev up and then back down again in the range of a few hundred rpms. Any Ideas?

Have you checked for vacuum leaks?

The engine was apart. Intake manifold, carb, spacer. Would the idle that wanders up and down be caused by a vacuum leak? I can't set the idle much since it will not stay steady. I turned both screws in all the way and then adjusted 1/4 turn out until the low part of the wandering was at 650/700. However, it won't stay like this for more than a minute or so, the wandering will eventually bring it too low and it stalls.

I am shocked you are having problems.

WhiteLakeSkier wrote: I may not have the degree, but I can easily do what the mechanic does.

I found that the erratic idle is because of a leak in the manifold, maybe even carburetor. I sprayed some starter fluid around the seals of the manifold and the engine would pick right up. Accurate? I also noticed when I took the manifold and carb off that there was two gaskets on top of the spacer, might be the source of some of my troubles eh?

When I put it back together, I know the hose from the spacer goes rear, however is it designed so that one side goes to the carb, one goes to the manifold? What do the correct gaskets look like for the manifold/spacer seam and the spacer/carb seam. I want to make sure it is all correct so I'm not doing this again.

Now the intake manifold gaskets, any specifc kind? I got them from pep boys last time for a 1984 ford 302 mustang car. All the ports matched up on the gasket and head. Do I use any sealant with the gasket? I used it last time just to hold it in place, and I applied a little more with the cork end pieces.

Other than carb, or vacuum leak issues, you may also have a worn timing chain. I put a new timing chain on when I rebuilt my engine, and it made a big difference....as well as following all the advice above. Before I did all those things, my engine (351) would also not idle below 1000 rpm.   

I took the manifold/carb off and replaced the gaskets again. All works great now. The idle is smooth and does not jump. However, I have the idle adjustment screw backed all the way out and It will only idle at 650/700. Shouldn't I be able to back it all the way out until it stalls? I have no wiggle room now, should it ever go higher, I can't adjust it lower. The gaskets are not leaking, as I have sprayed starting fluid around them all and no engine response from it. I took the PCV valve hose out of the cover and held my finger over it, didn't go any lower. Adjusting lean or rich has not helped either. Could it be the timing? The mark is not erratic at all. I had it set to 10 degrees advance, however the idle was even higher than. So I put it back to valve cover spec of 6 degrees and 650/700 is where I am at now. It just seems like I should be able to adjust it low enough to stall.

Alright, so is the accelerator pump idle screw separate from the screw that adjusts the throttle on the carb?

Luchog wrote: once you get to the 750rpms mark again, start tuning the iddle mixture screws again. If you close them all the way and engine does not stumble, you iddle passages could be clogged.

If it doesn't stall then your not on the idle circut to start with and need to disconnect the throttle cable at the carb and adjust the carb and timing then adjust the throttle cable properly.


if you have been making these adjustments with the throttle cable attached to the carb disconnect it and see if the rpms drop I bet they do since the screw is all of the way out and the engine isn't dieing then the carb's throttle plate is being held open by the throttle cables adjustment.

The cable has not been attached at all, and I check the timing as I'm adjusting things. When I adjust the mixture screws equally the engine runs at the same rpm. Regardless of where they are set lean/rich.

I actually have the idle speed screw completely taken out, so that is not affecting the lever at all. I notice that the lever is not touching where the idle adjustment screw screws into. It is almost as if the carb has bottomed out internally.

Hmmm, How can I tell if it is reverse rotation? The motor spins counterclockwise when looking at the flywheel. I still need to get a vacuum gauge, do I just hook into the PCV line? It just troubles me that I cannot adjust the idle to stall. Something is not right and I don't know what else to adjust!

Yes, set at 10 degrees