78 G60 developed a miss

[G60michael]

Hi there everyone,

The other Week the old girl Developed a misfire, I diagnosed it to #4 Spark Plug, so I chucked in a spare Plug I found lying in the shed, and it temporarily fixed the issue. Then Last Friday I Was going over the road to help the lady pull out some, I had to go retrieve some cable from the paddocks, it became missing again and on the way up the paddocks, when I got back to the house, I pulled out #4 Spark Plug and chucked in another one, it made it better but not 100% perfect.

Its not getting any better, it is quiet a miss fire somewhere in the system, I have swapped out the Leads for some I got from a Wreck (Yes they may be dicky, though they may Still be ok)

A Couple of other points as well
- It has relatively new spark plugs in it
- It having some wiring faults at the moment, maybe some part of the issue
- It used to start first go even on Really cold mornings with a fraction of choke, and a couple of pumps of the throttle, and it fired up and purred like a kitten, Until Its been misfiring its never started first go

Things I think may be worth doing
- New Plug leads
- Check Coil
- Check Dizzy Cap and rotor button

I don't want to spend money if I don't have to, its a basher but it needs to be reliable, overall its been awesome so far, few little issue but nothing has stopped her.

Any ideas or Suggestions will be awesome as, thanks in Advance

[RiverPatrol]

What did the spark plug look like when you pulled it out? Was it oil soaked? Was it burnt? When was the last time you adjusted the valves?

[G60michael]

What did the spark plug look like when you pulled it out? Was it oil soaked? Was it burnt? When was the last time you adjusted the valves?

Leslie I did them a While Back, wouldn't be even 12 months ago I don't reckon, There is a Pop out the exhaust occasionally, I assume its a Stuck Exhaust Valve, I do think its #4 or #5 Cylinder as I know when I went to adjust it wouldn't go its been like that for years and its 4 years of owning it now

[G60michael]

It wasn't oil soaked the other day, but if it helps ill pull all 6 Plugs out this arvo and Grab a photo.

[Johnny Roadkill]

Just going through what you've said so far on this one - if you're seeing an improvement after replacing just one plug then it seems likely you've correctly diagnosed #4 cylinder as the ugly one.

To me, that narrows it down to
a) something about cylinder #4 ( compression problem, valve seal leaking oil or valve being "held up" off its seat ), or
b) whole ignition system is slowly losing the battle and #4 is the weakest link - possibly because of the above problems but a less severe case thereof - and plug #4 gives up firing first as the HT voltage drops.

Without spending any cash, you could try
1) replacing the coil with a known good one, and eliminate that possibility straight up,
2) hotwire the coil +ve from the battery temporarily to rule in/out bad wiring in the ignition circuit,
3) compression test, which will show up bad rings or sticky valves,
4) if nothing improves or reveals itself after that...call an exorcist !

cheers,
D

[G60michael]

Wel today I Drove it out the shed, Started straight away with some choke, and ran like a Clock Drove it around for a while, Ran beautifully

Whats the old girls Caper

[Johnny Roadkill]

...call an exorcist !

starting to look more and more like your solution
cheers,
D

[Swerve]

Question Mike, are you doing the Mechanic Apprenticeship ?

[G60michael]

Was Steve, done a year of it, then the owner employed another full Qualified mechanic