looking for a miss

[topwater]

looking for the cause of a slight miss at idle i found that if the PCV valve is plugged the car smooths out. no miss. any ideas why. 88 lx stick

[91_festy_Gl]

Bad plugs, bad wires, bad disty cap, bad rotor?

[topwater]

thanks but ive done the tune-up. failed CO part of emissions test (running rich) so i gave up on finding the problem and sorted it with a little chem101. the 88 lx was a bit drunk for retesting

[ShagFestiva]

bad blowby?

[gorgonheimer]

Oil change. You would be surprised

[topwater]

thanks but i did change the oil. i also thought blowby could be high, so i plugged the PCV valve for the emissions test. i know its a cheap part but how much should the PCV valve vent?

[91_festy_Gl]

Advance the timing so its leans out, then try the emo test.

[gorgonheimer]

A pcv valve is a metered vacuum leak. Pinching it off changes your afr and also changes the combustion chamber chemistry. Fuel vapors and gases from the crankcase are routed into the intake to be burnt.