problem : Hesitation/missfire at low RPM particularly when pulling away.
This seems like a common problem, I read through as many posts as I could find , here, Brickwerks, Golf and Polo forums...
lots of problems can be caused by vacuum leaks , so I replaced my vacuum pipes, checked for air leaks around the base gasket, the inlet manifold to head gaskets , I checked the operation of the pull down unit, and the vacuum unit for the second choke... all seemed to check out... I had already rebuilt the carb 2 years ago with a kit from BW so thought that they should be okay, It still hesitated.
The exhaust was blowing, so I removed it and replaced all the snapped and sheared studs ( sounds easy when written in a single sentence , but oh how I laughed whilst doing this job
) I know that poor back pressure can cause issues, but still it hesitated, I replaced the thermostat and housing ( dont even ask about that job ) as it was stuck open so it took an age for the temp to come up, I thought this may have an effect ( possibly carb icing ) still no joy.So last night I took the carb back off, split open and went through every jet, removed and cleaned .To be honest everything looked fine, then I took a look at the accelerator jet.... this is operated by a cam mechanism with a vernier gauge so there is obviously room for adjustment, I took the diaphragm out to make sure that it was intact and no splits, all good.
on reassembly I rotated the mechanism so that the pump gives the squirt earlier as you open the throttle. I think what was happening is that there was a delay when the venturi flap was opening... causing an imbalance in the fuel air mixture, causing it to lean out too much and splutter.
I refitted this AM and took for a drive, it seems so much better, no more needing to give the engine a rev before trying to pull away, no coughing and spluttering . So fingers crossed , this has been annoying me for years so I hope it is all fixed.
This may be of help to others with a similar issue.
I still need to borrow a timing light to get that spot on, and the idle speed is done by ear , but I am happier that I think one more problem is now sorted.
