258 carburetor adjustment

You are supposed to first make sure you have the computer out of 'limp home' mode or the engine will run like a bag of dirt. To do this you use the 'Nutter' bypass which hooks the ignition module directly to the distributor.

I use 2 new wires and just hook the orange and purple wires directly together at the distributor and module rather than mess inside the wiring harness. Here is a link on it:

Once the timing is set, you start with the idle mix screws 5 or 6 turns out. The engine will run like this, but the idle will need adjusting.

You get it running and start turning both screws in 1/4 turn at a time. Between each turn, you give the gas linkage a shot to rev it up. Continue on, maybe adjusting the carb every time it goes off 50 rpm, until the engine starts to lean stumble. It will be obvious when that last 1/4 turn makes a difference. You then back both screws off 1/4 turn and you are god to go.

mark wrote:

I did the bypass and also have an aftermarket bbd with no wires and a manual choke. The EGR is unhooked and pluged at intake and exhaust manifold. O2 sensor disconnected. I tore apart the carb today hoping to find some dirt in the idle tubes but they are clean (years ago I drilled them out to 0.032) I took off the intake manifold hoping for a cracked gasket but it lookes great but I think I will add an extra gasket anyway. Should the mixture screws be adjusted the same? 1 was out 2.5 turns and the other was out 4.5 turns. Could this be part of the problem? The symtoms feel like it is not running on all cylinders. Plugs, wires, cap and rotor all new. It does seem to idle all right but stalls easily when givin too much throttle.

They need to be the same. Sometimes a spring is weak allowing the one to loosen and sometimes someone loosens one to make up for a plugged idle tube.

2.5 turns is pretty lean. That will cause a rumble at idle in half the engine while the other half is idling rich. Should sound fairly strange....

Mike

mark wrote: