Idle Problems

[oldsalt23]

I receently changed my points and cleaned my carb. Now my engine will not idle with the choke open below about 1500 rpms. If I throttle back any further it stalls out. With the choke closed I can get it down to about 1000 rpms. Any Ideas. Please respond to oldsalt23@yahoo.com. Thanks Jim

[jarod]

I just recently had issues with my A4 at idle. I would first pull the plugs to see what they are doing. If they are black (carbon fouled) I would consider the following possibilities:

The needle valve for the float has some crud under it which is affecting its ability to close (hence the overfueling). You can confirm this by pulling off the flame arrestor and running the engine to see if there is fuel pooling in the throat of the carb.

You may also want to disconnect the linkage for the choke to ensure that it is not the choke sticking partially closed...you should be able to confirm this when you pull off the flamer arrestor though (see above).

You could also consider a blockage or a low point in the exhaust line that is causing excessive back pressure (this was my issue) and it was a simple matter of modifying the exhaust outlet hose so that it was at a slight decline to the exhaust outlet.

The issue could also be related to some electrical issue so ensure you have the plug wires hooked up correctly and if there is a variation on the sparkplug colors you would be more inclined to think electrical...for instance if you have one plug that is black but all of the others are a nice light grey or brown.

ALSO DON'T FORGET ABOUT MOYERMARINE.COM AS THIS IS THE PLACE TO GO FOR GOOD INFO ON THIS ENGINE...A GOOD FORUM AND DON MOYER IS ALWAYS THERE TO HELP YOU OUT WITH YOUR QUESTIONS...

[Idiens]

My guess, from what I understand you describe, is that your engine is running too lean. It needs the throttle open far enough to suck enough fuel. If I am right, you may find the plugs are pale after a run to get the engine warm at 1500 rpm, no choke. That suggests that when you cleaned the carb, you changed some setting. What, would depend on the type of carb. It could be a main needle valve, or the tick-over bypass valve. It could be the float height (my first bet - check the yoke orientation). But like jarod suggests, check the plug colours.
If it were electrical, it may be affecting only one or two cylinders, then the plugs would different colours from each other, but your would hear that at low revs. If the CB points are very badly set, it could have too much advance or retard.
You need to provide more infromation.