Bus owner: Might be a broad question, but what is the main cause of a rough and sputtering idle with a cold start. 1978 Westy Fuel Injected. the bus really sputters and struggles for the first 1 minute or so. Thanks!
Intelligent Tinkering: Poor idle on cold start is typically mixture too weak, whether EFI or carbs. The gas has to vaporize correctly for the motor to settle down. If it fires up right away and then runs rough, the cold start valve is probably working (and so the thermo-time switch is too), so I would suspect fuel pressure or some other aspect of fuel delivery after the cold start sequence. If it doesn't fire up right away I'd suspect cold start. You would have to rule out weak compression and bouncy timing issues to be certain. Thin rings or a worn distributor driveshaft wouldn't help matters either. But everything is relative. How rough is it? A lot of VWs are like this. I have a 75 with twin carbs that fires up right away and then likes at least thirty-forty seconds to settle down before you can goose the throttle. A second too soon and it will cut out. It then proceeds to run like a top all day. You could take the Zen route and use those few seconds for something else. The "How to Keep your VW Alive" author, John Muir, suggested rolling a hand-rolled cigarette while waiting for the engine to settle. I suppose these days we would all check our phones.
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