Poor running at low revs, cuts out

[walkinginperu]

Hi guys,
My 1.6GT manual on a weber carb has started messing me about. It starts and drives, but at low revs and idle there's a vibration from the engine - feels like it's missing. If you give it a bootful it seems to smooth itself out, and on the road it's ok as long as your going at full chat. But obviosuly this isn't great in the ice and snow as I don't won't to crash and die . I've cleaned out the carb, checked the plugs, changed the fuel filter and air filter and ht leads, and even sworn at it loudly in front of the neighbours. Anyone have any ideas before I take it to the garage round the corner/hit it with a tree branch in the style of Basil Fawlty?

[MikeH]

The vibration is probably just due to the low idle speed. If you've checked the basics (sounds like you have) then timing is next, and maybe the carb setup. If the timing is a little retarded, a car will tend to tick over slower, and not pull well at low revs. You could mark the position of the dizzy and try adjusting it by ear a little. If I don't have a timing light to hand, I advance the ignition till it ticks over smoothest and quickest, then back it off a smidge. Take it for a test drive and re-adjust if it's pinking. Mark the position before you start though.

[walkinginperu]

Thanks for the reply mike. It's not a vibration due ot low idle speed, the vibration is present all the way up to about 3500rpm at part throttle. I'll check the timing but I'm fairly sure it's on the money.

[markh]

It could be down to an air leak from the carb gaskett, inlet manifold gaskett or split vacuum pipe.

[walkinginperu]

Took it to the garage in the end, they diagnosed failed inlet manifold gasket as markh suggested. They've replaced it, now it idles at 1500rpm so i need to sort the carb settings out.

[walkinginperu]

Quick update for anyone who's interested. Car was idling at about 1800rpm by the end of the week so opened the bonnet this weekend to sort the problem. Found the the airbox hadn't been reattached to the carb properly, which was disappointing from a garage. This had been contributing to the dodgy idle speed, but garage man had tried to adjust the CO to match the wrongly attached airbox = VERY rich. Fiddled with the carb a bit to reduce idle speed, discovered the misfire was still there and the high idle had been covering it up. Checked dizzy cap (garage said they'd done it) to find it was, in technical terms, ffffffd. Got a new one from gsf and swapped it over, misfire gone. Idle still rubbish.

[christhemann]

Hi mate,
I almost feel your frustration! Very annoying.
So it looks like the garage were wrong about the inlet manifold gasket, and judging by them messing
up putting the air filter back on i'd be tempted to leave them along in the future!
Have you tried spraying some carb cleaner or wd40 around the carb gasket as well? The rubber joint between carb and inlet manifold are apparently a common cause.
Did you already reset the mixture screw on the carb? To do this, first make sure the timing is set correctly and get it idling around 850rpm. Then turn the screw in slowly until the idle drops considerably, back it out slowly to get the highest idle speed possible (stop once you reach this). Then give it another 1/4 turn clockwise to finish off.

Otherwise, sounds like you checked the obvious ignition components already...
Is the alternator and battery charging properly? Best check the voltage is over 13v at idle.

Can't think of much else right now, good luck