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Engine miss when hot

Posted: Sun Sep 30, 2018 2:32 pm
by John Alves
Hi all
I have a new addition to the family, a 1968 1500sp beetle which I am slowly sorting out.
The latest issue is a slight engine miss when cold, after the motor is warmed up, she runs like a bomb,
Any ideas on trouble shooting this?

Re: Engine missing when cold

Posted: Mon Oct 01, 2018 2:53 pm
by 73type2
Perhaps electric choke is not set correctly?

Re: Engine missing when cold

Posted: Mon Oct 01, 2018 3:29 pm
by fig
Check your manifold heat risers. They are probably blocked.

Re: Engine missing when cold

Posted: Mon Oct 01, 2018 3:39 pm
by Tony Z
fig wrote: Mon Oct 01, 2018 3:29 pm Check your manifold heat risers. They are probably blocked.
aftermarket exhausts sometimes have ports for the heat risers, but they are usually designed wrong and dont allow flow, so they block with carbon

also, check for vacuum leaks

Re: Engine missing when cold

Posted: Tue Oct 02, 2018 11:50 am
by John Alves
choke is working, heat risers are blocked off, my other two air cooled cars don't have heat risers and have no issue ????
I have checked for vacuum leaks, will check again
did all the usual when I bought the car, points gap, valve gaps new plugs, set timing, replaced dizzy cap with one I had lying about.

could it be a sticking valve which loosens up with heat?

Re: Engine missing when cold

Posted: Tue Oct 02, 2018 11:59 am
by Tony Z
try advancing your timing 2-3 degrees

Re: Engine missing when cold

Posted: Fri Oct 05, 2018 6:37 pm
by John Alves
thanks Tony that did the trick

Re: Engine missing when cold

Posted: Mon Oct 29, 2018 9:44 am
by John Alves
Worked for a while and them came back with vengeance, I replaced the dizzy and coil from my other ride and all is 100% now.
Could it be a faulty Chinese condenser? I don't have a spare condenser as all my other rides have been converted to electronic pick up

Re: Engine missing when cold

Posted: Mon Oct 29, 2018 9:47 am
by retrovan
Bash the sides of the condenser with the flat side of a spanner, and it will work again,

Till you can get a Bosch condenser from Diesel Electric.

Herman

Re: Engine missing when cold

Posted: Sun Nov 18, 2018 4:17 pm
by John Alves
The saga continues, I now have a minor miss when cold, runs ok for about 20min and then miss comes back when engine is warm, It feels like a total loss of power but for such a short time and not steady, I connected a multi meter to the coil positive and ground and as the miss happens so the voltage drops to about 10v then back up again,
Is this an indication of a intermittent short on the coil power wire or could the voltage drop also be caused by something else?

Re: Engine missing when cold

Posted: Sun Nov 18, 2018 4:54 pm
by retrovan
Still sounds like a condenser.

Or bash the bottom of the condenser with the round edge of a 19 spanner to dent it.

But to be sure, fit a blue Bosch coil

Herman

Re: Engine missing when cold

Posted: Sun Nov 18, 2018 5:12 pm
by John Alves
not using a condensor I switched to a working dizzy with igniter system

Re: Engine missing when cold

Posted: Sun Nov 18, 2018 7:02 pm
by Tony Z
ignitor system isnt reliable

Re: Engine missing when cold

Posted: Sun Nov 18, 2018 7:28 pm
by John Alves
I know, but this one was taken from my ghia and is working

Re: Engine missing when cold

Posted: Mon Nov 19, 2018 9:34 am
by retrovan
May be incorrect coil for the ignition, try moving the coil from the Ghia with the unit and try again.

Herman