1967S starts great, runs great, popping on light throttle only

[jim schrager]

67S SRW Targa, starts and runs great, pulls hard, idles well, no popping on over-run, but pops randomly on light throttle at about 4K RPM. All idle jets and main jets are clear. Completely stock. Survivor with mostly original paint and 150K miles. Has Permatune, stock carbs, and stock distributor. Does not eat plugs. Looking for ideas. Thanks, Jim Schrager

[Orval_F]

You may have air leakage around the throttle shafts.

[edmayo]

Which carbs? IDS with high speed enrichment, or IDA with an 'S' stamp without high speed enrichment? and what is current jetting? Have you tried a one size up idle jet just to see if that helps. Do you have access to a A/F ratio meter so you can see exactly what the mixture is?

[jim schrager]

Which carbs? IDS with high speed enrichment, or IDA with an 'S' stamp without high speed enrichment? and what is current jetting? Have you tried a one size up idle jet just to see if that helps. Do you have access to a A/F ratio meter so you can see exactly what the mixture is?

Thanks Ed. Stock Weber IDS carbs. Car did not do this a year ago, and I have not changed the jets. I can pull to look at them, but my sense is they are the ones that came in the car, as it is dead stock. I do not have access to an A/F meter but do have extra jets so may move one step up on the idles. This is a car I have had for many years and it has never had this symptom before. Thanks, Jim S.

[edmayo]

Jim, If I remember correctly, you posted earlier that this car doesn't get driven regularly, so even though nothing has really changed to cause this, time and dirt may be your enemy. When cars sit a lot small particles can solidify out of the gas, like sugar in the bottom of a coffee cup. It doesn't take much of a particle to partially clog an idle passage. I'd suggest removing the idle jets, and the idle mixture screws. Use a aerosol can of carb cleaner with the long plastic nozzle, spray it in the carb where the idle jet came out from. Flush it real good and blow out with compressed air. See if that cures the miss.