My '89 RS has a 305 TBI that recently started to miss while under load at low RPM(<2000). Three years ago I put a Crane multiple spark module on it (HI-8, I think its called?), and its run fine until about a week ago. It now seems to drop a cylinder going uphill, or when trying to accelerate too quickly, occasionaly backfiring through the intake. It idles fine, and above 2000RPMs the engine accelerates smoothly, but for a couple of hundred RPM it shakes and stutters. I've replaced the spark plugs, the cap and rotor, and the ignition module on the distributor, but the problem hasn't gone away. Twice in the past week it has refused to start, it would turn over but not fire, and when I let off of the ignition it would stop and then give one last spark after about a second of dead time. After a couple of minutes it would start, but ran rough for a few seconds before the idle smoothed out.

I'm not sure what the problem is. I thought it was in the ignition side of things, but now I'm not so certain. I suppose it could be the ignition box, or maybe the computer itself, or I could be completly wrong. If anybody has any ideas, I'd sure like to hear them.

 

sounds like it could be your fuel. check the pressure in the line.

 

Wouldn't it run roughly at idle if the fuel pressure was low?

 

Not necessarily.

 

you replaced plugs, cap and rotor already, why not the plug wires?

I agree though, it sounds like a fuel problem. Check your fuel filter before you go out getting a new fuel pump

 

The distributor hold down bolts had come loose. Timing was 12* advanced. Backed it back to 4* and it seems to run fine now.

 

That'll do it.