Uneven Idle

Post by **David53** » Wed Nov 11, 2009 4:36 am

My engine is still running unevenly at idle. Distributor is fully rebuilt, including new Vac Advance unit. I have set the timing at around 12 TDBC but will perhaps try advancing it a little more bit by bit.

Is there anything else I should be checking? Mixture seems about right, plugs are light brown. No noise from valves, compressions are OK (125 across the board, low but that's normal for an 803).

Car runs well under power but idle is uneven and a little "jerky". Any thoughts welcome

Post by **kennatt** » Wed Nov 11, 2009 8:09 am

inlet manifold leak maybe

Post by **beechford** » Wed Nov 11, 2009 10:47 am

give it a chance to settle .youve done a lot of work to it now relax let it settle.

Post by **Kevin** » Wed Nov 11, 2009 3:48 pm

You have set the choke correctly I suppose.

Post by **mike.perry** » Wed Nov 11, 2009 4:10 pm

See my reply to your PM

Post by **bmcecosse** » Wed Nov 11, 2009 8:07 pm

12 degrees advance is far too much - something wrong there! Are you measuring that 'advance' while the engine is running - and if so - is the vacuum advance connected ? Needless to say - it should be dis-connected! Did you come back with the stamped figure for mechanical advance in the dizzy - I can't remember now! ??

Post by **David53** » Thu Nov 12, 2009 4:43 am

The only number on the weights was "9", not sure what that related to.

Petrol here is 93 Octane Unleaded which is why the spark is so far advanced. And yes, choke is fully off when idling, and as far as I can see it is fully released at the carb. Speaking of choke I need it to start the car from cold but once running I need to push it in almost immediately or the engine will run too rich and stall. She warms up after a few minutes and idles with no choke but till then need to keep the accel down a little.

Will have a further fiddle this weekend (with vac disconnected

)

Post by **bmcecosse** » Thu Nov 12, 2009 2:01 pm

93 unleaded should mean somewhat retarded ignition - not advanced! You need to screw down the choke idle screw - so you get more revs with the choke out - to stop it stalling. you should always need a some choke to start -about half in summer, maybe ALL in winter. Then almost immediately should be able to ease it back in slightly - just leaving a 'fast idle' for a minute or two - and then completely in.

Post by **PSL184** » Thu Nov 12, 2009 4:55 pm

It may just be running slightly rich at idle. Could be float level not correct and flooding over the needle. It will be fine when running at speed as the extra fuel will be burnt but it can give a slight stumble at idle....