LEAN MISFIRE

[1983wagon]

G'day guys
I have recently rebuilt my ea81
I broke a bolt in my manifold so I had to replace that. Ever since I did I had
been misfiring after it was warmed up which was about 5 mins after driving... I
changed the coil and resistor and it seemed to have fixed the problem. For about
45 minutes anyway of driving. It's not doing it anywhere near as bad as before I
changed the coil and it only does it after a good half hour. It's not pinging
lets make that clear... I can pull the choke out a bit and sometimes makes it
stop for a few seconds which leads me to think she is hungry for more fuel. But
why does it start doing it after some time of driving and not right away???

I've put new plugs and leads and all tested fine. I've checked all bolts to
be tightened and vacuum hoses all check out ok. I changed the EGR valve to check
if that was the problem but still no good. It doesn't matter how soft or hard I am driving it will still do it.

It doesn't misfire at all when idling.

Let me know what you guys
think because I may be missing something. Any more info you guys will need to
know I will answer as soon as I can
The carby has been rebuilt.
(Professionally) and am wondering if it needs to be tuned in some sort. The next
step for me will be taking it to the carby shop because I have literally checked
everything !!!

[NorthWet]

Since it started after you diddled with the intake manifold, I would be inclined to start there.  Have you checked for vacuum leaks, such as at the intake gasket or a vacuum hose that has gone askew?  My reasoning here, other than what was last changed, is that supplemental fuel (choke) helps.  The mixture is naturally leaner when the engine is up to running temperature and at cruise power.  When cold, it is getting extra fuel due to the choke, and idle runs richer, too.  A leaner mixture puts more demands on the ignition system, which could explain why changing ignition parts helped a little.

 

My money would be on the intake gaskets at the head.  I understand that with the later EA82 that Dealer gaskets are preferred due to greater thickness making them less leak-prone; not sure about EA81s but would imagine the same.