Hi Im new to aircool (4 weeks to be exact) so please be gentle !! I have 1973 Automatic Type 4 engine (all recently serviced by vw specialist) with weber single prog carb The van starts first time and idles no problem - great Drives great when warm........ BUT When starting from cold the van starts and idles perfectly BUT when I put it into Drive or Reverse (automatic) van revs drop slightly ....... still ok ........ as soon as I put my foot on the accelerator the revs drop more, stutters and the van stalls. I have to do this several times just to get out off my driveway. Eventually I get on my way after 5 mins. During the first 10-15 min of driving every time I stop the van idles no problem UNTIL I put my foot on the gas and it stalls. The only way I have found round this issue is to gently pump (tickle) the accelerator pedal quickly before I set off !!! Any ideas Thanks
Sounds like the choke is acting up to me. If it has an electric choke un plug the wire to it and see if it acts the same, if so the choke needs attention.
Could be carb iceing up,check when cold, you can see ice on carb and top of manifold, clears when engine warms through. Usualy worse with after market carbs and air filters.( is your bus a yellow aussie import?)
Has the carburettor been recently fitted to replace fuel injection ? The progressive carburettor 'out of the box' is supposedly jetted for 'a standard engine'. It isn't ! Nowhere do they say what that engine is - as the same carburettor can be used on a lot of different engines, the settings will be wrong or more wrong. There are several possible problems - I have this carburettor but with 1600 engine and a manual transmission so not all these may apply but : One possible problem will be that the choke plus standard jetting (??60 idle, 140 main) makes the mixture extremely rich when it is all working properly, so the spark plugs foul up and you lose power. I see lower than 10:1 AFR (I have a wideband O2 sensor/display) while the choke is on, even with 'lean' jetting on the primary barrel. Once the choke comes off the plugs clean up a bit and the engine runs better (SGS Aircooled suggested this was going on) . This one drove me mad, I thought there was something badly wrong, until I got the wideband system fitted and started re-jetting the carburettor. I currently have 45 idle , 125 main. Another possible (opposite) problem (giving flat spots) is that you will need warm air feed to the carburettor from the cylinder head while warming up. If you dont have an original air cleaner setup with a warm air feed from below the tinware, some petrol stays as pools of petrol rather than vapour in the manifold. This means the engine will run leaner than it should . And when you open the throttle, the reduction in vacuum caused by the carburettor venturi effectively getting larger with the same airflow total as the second carburettor barrel comes on line means that the engine runs lean causing yet another flat spot. (it blips past 15:1 when I press firmly on the accelerator). To partly fix that I have 70 idle and 160 main jet on the secondary barrel, and 160 primary and 180 secondary air correctors. And the throttle positioner for an automatic is probably not set up right for the progressive carburettor. Some of these things will appear on the rolling road and can be tuned out but some of the flat spots may persist as they involve combinations of engine load, speed and speed of stamping on the accelerator. Good luck.
