Lumpy Accelerating

As the title says, when I pull away from either a standing start or just pulling away from a slow corner my engine is is very lumpy. But once it gets up to speed it will happily go through the gears with out a miss fire or problem.

Any ideas what could be causing this? Its just a standard 1600TP and carb. Only differencefrom stock is the airfilter and exhaust.

 

No it seems to idle fine once it gets up to temp. When it cold it needs a slight blip sometimes but once the choke is off its fine.

 

Different setup (Bay with type 4) engineby I tracked my lumpy accelleration and missfire to three problems.

1) Leak in the vacuum pipe from manifold to brake servo
2) Leak in balance pipe between carbs
3) Worn carbs

Replaced carbs, fixed leaks and it went from a misery to drive to super smooth.

My guess is you have an air leak in the induction system somewhere.

 

Cheers I'll trace all the vac hoses and induction. Sounds cheaper then new carbs

 

What he said ^^^ check for air leaks

 

My guess is you're expecting it to accelerate at low revs, but I'd check the timing.

 

I had a similar problem last year and that turned out to be a split in one of the carb balance pipes. 50p for bits and the motor was sweet as a nut after.

 

Thanks everyone, first thing ill be doing is replacing the pipe's. it did have a new engine fitted just over the year ago by the past owner but looking at the vac lines he used the old pipes.

 

Non stock airfilter - Will be letting in cold air where a stock airfilter and preheat would not.
If its shiny chrome and on top of the stock carburettor, expect problems on cold days.

Missing or leaky vacuum pipe will not help ignition advance. Extra points lost for leaving open end which would have gone to thermo valve on stock aircleaner, and on to preheat air flap.

Combine the two, add a possibly worn out carburettor spindle (if extremely worn , you can wiggle the throttle shaft and listen for the hissing changing ... ), and your bus will drive less well than it should..

And I probably ought to add my recently discovered recipe for rough running - having a distributor clamp that lifts the distributor away from the engine block. My original one was dished where someone had overtightened it, and that lifted the distributor about 1 mm. Bought a replacement EMPI chromed clamp from GSF (they had the grace to apologise for the chrome), and this one needed its fixing tag bending down flat because it sprung the distributor away from the engine block by about 2mm. Argh EMPI made In China Cheese Metal parts.