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bug missfire
booge - July 29th, 2012 at 10:19 AM

Hi everyone I have a 67 bug almost finished resto had it booked in for blue slip yesterday only the motor wont run properly I have changed plugs and leads rebuilt carby ajusted timing and points new condensor but sill no joy she idles a bit rough bit under load verry unhappy miss fires no power any ideas?

TorxKiwi - July 29th, 2012 at 05:41 PM

Are you sure you have the firing order correct?

http://www.vw-resource.com/misfiring.html 

Bob down - July 29th, 2012 at 06:06 PM

also maybe useful to work out which cylinder shes not firing on?

greedy53 - July 29th, 2012 at 06:44 PM

are you using a new dissy cap and condenser and leads i chased a misfire for blody weeks turned out to be a dicke lead
good luck

booge - July 29th, 2012 at 06:57 PM

Firing order looks ok have pulled a lead off each plug and runs worse each time so all leads work and plugs ok should I look at valve clearances or bite the bullet and take it to a mechanic

Sides - July 29th, 2012 at 07:33 PM

Hmm... could also be a result of "rebuilt carby"... when you put it back together did you set the mixture screw set correctly ???

Also are you sure the coil is good ???

IMHO tappet adjustment would have to be SEVERELY out to cause it to break down under load like you're talking about....

66deluxe - July 29th, 2012 at 07:35 PM

The worst misfire i ever had was due to a dud rotor button.

booge - July 29th, 2012 at 07:52 PM

Coil was my next move I also noticed when I pulled the tube off the Carby for the vac advance there was no real difference I have seen video of the motor changing quite a bit could there be a problem there ?

bajachris88 - July 29th, 2012 at 08:06 PM

have a read of this Misfire article from vw-resource.com. It may be of assistance.

http://www.vw-resource.com/wires_plugs.html#misfire 

booge - July 29th, 2012 at 08:29 PM

thanks i will look to see if i have the right plugs tomorrow its so frustrating to be so close after a 3 year build to be stumped by this

68AutoBug - July 29th, 2012 at 08:45 PM

Quote:
Originally posted by booge
Hi everyone I have a 67 bug almost finished resto had it booked in for blue slip yesterday only the motor wont run properly I have changed plugs and leads rebuilt carby ajusted timing and points new condensor but sill no joy she idles a bit rough bit under load verry unhappy miss fires no power any ideas?


When You say no power...
Can it be driven? I could never drive Mine when restoring it, but it started and idled perfectly... the accelerator pump on the carby was block by old fuel... [it still is, in the shed]
but Mine idled perfectly..
what about the distributor cap? wipe inside with petrol or metho or WD40 etc..
also check the rotor inside the dizzy cap..
they have a resistor in them to stop radio interference and they can burn out... not common but does happen..
also wipe it all over with petrol etc too..
make sure the coil is connected + to POWER
- to distributor as an engine may go even connected wrong way around...
All spark plug coil leads should be checked with an ohm meter
unless they are the original wire type..
as silicone etc can open circuit easily...
My new lead to the coil broke inside the lead first time I pulled it off the coil... sounds like a coil or dizzy problem..
is the engine earthed??? there should be a lead on the gearbox, other wise the power has to find its own way thru the gearbox etc.. engine & gearbox are on rubber mounts..

Better to try everything Yourself... unless You have a good VW air cooled mechanic nearby...
stay away from any other mechanics unless they are old and retired.. lol

cheers

LEE

68AutoBug - July 29th, 2012 at 08:51 PM

Quote:
Originally posted by booge
Coil was my next move I also noticed when I pulled the tube off the Carby for the vac advance there was no real difference I have seen video of the motor changing quite a bit could there be a problem there ?


mine doesn't do anything with any vacuum hoses off..
apart from stop the carby from advancing...
what engine and carby and dizzy are we talking about..

You have fuel [not old fuel] air, and need a good spark..
compression should be good...
tappets been double checked?
points correct? 1432 timing cylinders.
timing light at revs?
Dizzy 009?? or vacuum & mechanical [SVDA]
if its real bad idle, You haven't replaced the dizzy cap with one from another dizzy as the caps can be different and the rotor is the correct one for that distributor..?

LEE

booge - July 29th, 2012 at 09:04 PM

I know of a mechanic in Sydney not far from me you might have heard of him Andrew in north rocks Rd push come to shove will tow to him
thanks to all for your help will let you know how we get on

ian.mezz - July 30th, 2012 at 07:04 PM

did you put a fresh tank of petrol in him.
It may help to hold the revs up a bit to get any old petrol out of the system.

booge - July 31st, 2012 at 04:52 PM

she is booked in for Thursday week at Andrew Dodds for repair I am dying to know what he finds once again many thanks to all for your advice I will let you know the result

psimitar - August 2nd, 2012 at 10:27 PM

Sounds like an air leak. best thing to do is use some 180 grit wet n dry on a flat pane of glass and some wd40 to sand the manifold flanges flat and also the underside of the carb.

Go to a motor factors and buy a roll of oil resistant gasket material. Should be 1-1.5mm thick stuff. Cut all gaskets from this and this will ensure that everything seals well on re-assembly. The metal inlet gaskets only work well once and only with perfectly flat mating surfaces.