Okay, going back a ways I've had a 401 code for about a year. Last week the car started bucking real bad. Not all the time though (seemed like just whenever the AC was on). Then pulled a 420 code (Bad Catalyst)

I went and did a complete manifold clean job. Put it all back together and still got the bucking. Got a CEL, now just says a 320 code.

Installed new plugs and wires, reset everything, another CEL, another 320 code.

The 320 code is the ignition/distributor engine speed input circuit I believe. A few questions...

1. Why didn't the 320 show up whenever it started to buck the first time?

2. What's up with the mysterious 420 code?

Don't want to throw parts at it if I can help it. The help so far has been great. I can't seem to find any thing on this new code though.

Thanks