Update:

Jcyuhn: Symptom is not present at cold startup. I'll have to check, but I think O2 sensor is original. Would you recommend replacement as a matter of preventative maintenance?

Mr. Dalton. Thanks for pointing me in the direction of the purge valve.

I plugged the hose on the intake manifold side of the valve, then drove the car. If anything, the symptom seems to be worse. I removed the valve and found about a half tablespoon of what I assume are charcoal granules in the upstream (canister side) valve connection nipple. I suspect that these came from the evaporation canister located upstream of the purge valve. Does the presence of these granules indicate anything? Could they cause the valve to not function correctly? Could a plugged vent line to the canister change the air flow path through the canister thus drawing granules to the valve?

I’m going to look at the canister this afternoon to see if there are any plugged lines. Also, next time the symptom presents itself, I’m going to remove the gas cap and see if that has any effect. Could it be that idle hiccup/burble is the result of excessive vacuum in the gas tank?

Thanks for the help so far.

Any other ideas?


J. M. van Swaay