Scirocco Register

Thought i'd sorted this, but went on a run over to stoke with jay's big trailer on the other day, and it's still happening.
'92 GTII /Weber. Coming down to junctions, roundabouts etc on quick roads, it tries to tick over at about 200 RPM. blip the throttle or yank the choke out and it rectifies it.
fuel systems all been off/cleaned/replaced. Had it tuned a few months back by a guy who's meant to know what he's doing (before sorting the fuel system, admittedly, but I set it back up to the numbers that he got off his crypton using my CO meter/strobe - so it should be right!) It's had new plugs, recent leads/dizzy cap, I've changed the ignition module, carb's been off/apart/cleaned/back on, air filter's new (fram filter/stock air box, but with vacuum flap removed, so constant hot and cold air pickup) and all pivots etc on the carb have been oiled. Carb mounting's not cracked. Breather pipe's disconnected at the moment, (blanked on airbox, so not sucking un-filtered air) awaiting a day to fit oil catch tank. Vacuum pipes have all been replaced, brake servo's behaving itself.

Only thing I know's wrong is the battery. It's too small, It was practically new on my old polo, so it seemed rude not to pop it on. Starts the car fine though, so I can't see that could be causing issues 100 miles into a run!

Annoying thing is it's running beautifully! Quiet, smooth, OK on fuel, picks up brilliantly... Best it's ever been, in fact!

So why's it being naughty?

has it got an inlet filter on the carb? (big nut underneath the fuel inlet) have you checked it? if these get wet they fill up with white furry stuff, if it has, clean it ut and chuck some wynns dryfuel in the tank

how old is the carb? diaphragm split maybe?

Yep. I took the inlet filter out/cleaned/refitted when I stripped the carb. Looked clean before. Inline fuel filter gets renewed pretty often, so practically no dirt's got through it.
Carb's a bit over 2 years old. No aparent damage to diaphragm.

My Dad keeps telling me to ring Webcon, and check i've got the right jets in the carb. (despite the fact it was bought new for application) But I can't comprehend it could run so well the rest of the time if they were wrong.

Do we know jet sizes?

have you ever had it running right with that carb on?

what state are you ignition components in? (and don't just say "replaced 2 months ago" etc., actually check them!)

Had it running problem free with the carb on. Anticipating all's well with the ignition... Been advised by GTMatt (based on his remarkably similar experience) to change the needle valve in the carb. (Didn't change anyhting when I stripped it - was expecting to see a blocked jet or dirt or something, so it was just a strip to clean.) Going to get a rebuild kit (today, hopefully) and sort it out.

Been having problems with the car for a while (months) and have changed everything on the ignition bar the dizzy itself during this time. Will check later when I'm playing with it though...

Needle valve changed. All seems sorted. Only been out 10 miles at a time as yet though...