TheSamba.com :: View topic - 78 Bus

Tue Jul 22, 2014 7:05 pm

I'm working through my 78 Bus and it's getting a bit better each bit I do.. Cold starts are now fine - reconnected a vacuum line to the auxiliary air valve and it works great.

My issue I'm now focused on is rough starts from warm-ish temps.. warmer than where the AAR kicks in, but fully warmed up - like if you shut the bus off for an hour. It will start really well, but then within a few to several seconds the idle gets very very low and rough, almost stalling (sometimes does.) I can restart and give it a bit of gas for about 30 seconds and then it's OK. When it warms up fully it's fine.

I have been all over the vacuum hoses - replaced a few. The S-boot is like new. Interestingly the PO, or his mechanic, had the idle mixture turned fully rich. Carb cleaner sprayed around the throttle valve seems to raise the RPMs interestingly, though everything seems tight there.

Any oddball stuff I should be checking? I've been all over Bently's and this site.

I need to get away from this tonight.

Tue Jul 22, 2014 10:10 pm

You might try a new TSII sensor. The Vanagon Bentley gives a chart which shows what the resistance is supposed to be over a wide range of temperatures, while the Bay Bentley only give the resistance at one temp IIRC. Corroded wiring to the TSII sensor and resistance between the sensor and the head will affect how the engine runs. Using never seize on the sensor threads is a good idea.

Wed Jul 23, 2014 9:45 am

TSII made a big difference for me.

If your rpm's go up when you spray the throttle it means there is a leak, have you take it off to inspect the area? There is a gasket that goes in between the TB and the intake plenum.

One big leak that took me ages to track down was the cold start valve, so make sure to check absolutely everything that connects to the intake.