electrical issue - miss in spark

[mahse]

Hi all,
First off great site, have seen some really good feedback from here.
I have just aquired a 89 gq 4.2l carb/petrol only lwb.
It idled at 2g when I got it, new plugs, clean dizzy, leads not tracing and now idles at 900, I'm happy with that also had 4kg of oil pressure at idle but dropped to almost nothing at revs, changed oil and filter and now idles at almost nothing but rises in revs, also tappet noise is now evident.
(Valvoline xld 20w50).

After all that now its got a Huge miss, on and off load, even on idle,

I've tried new balast, new coil, new points, different leads(200k old) and no change, tacho goes all over the shop,
Sprayed wd40 over manifold gasket, no change. I have a fairly decent exhaust gasket leak and a crack in manifold.. how exhaust sensitive are they?

Carb is fine on it, it use to cold start on the first revolution but now ya gotta flog the loud pedal to get it to happen, Iknow that makes it sound like fuel issue but next time it starts fine.
Hot or cold doesn't seem to affect it, more how its feeling atm.

It always had a intermittent miss but now its huge.

That's for hearing me out.
Cheers
Mike

[threedogs]

Hi Mate and welcome to the forum, have you fitted the extended rotor button yet,
from the sounds of it looks like it needs a decent service,
Some of the GQ boys will be along soon to assist
How old are the leads??

[mahse]

SCheers mate,
Yeah all serviced now except for leads, there top gun and look fairly old,
Upon installing new points she now just starts but any attempt to rev it and it dies, I used same method as always, ( set it on a lobe insert feeler guage, tighten screws, )
I've seen a bit about theextended rotor but struggle to undersrand y factory oem is no good. Also with the dizzy caps does the contact point from the cap to button move on a spring like every other dizzy cap I've even seen, coz this one is fixed position and with a dop of oil test doesn't seem to b making cintact
Cheers

[threedogs]

check all the vacuum lines they may be all perished.
Might want to pop over to the intros and say hello and tell us a bit about yourself and your Patrol.
just something the forum asks of us all

[GQ TANK]

The gap with stand points is too wide - the extended rotar button helps.

I would consider a carby kit, you could have some blocked jets -

Also set the tappets they should be a little bit noisy

[mahse]

Cheers but what about dizzy cap contact point to rotor?

[warner01]

me and my father inlaw added some more to my exsisting rotor button by welding to the end then shaping it after. worked really well. also i had an intermit miss that took me a while to locate plus tacho was all over the shop. that turned out to be the guy i bought it off had used the wrong nut on the negitive side of the coil and it didnt actually tighten on the wires properly. after fixing this it worked perfect. also it sounds like you did your points correctly so your on the right track.

[rustbucket89]

With the tachometer jumping all over the place I would suggest it's more to do with the condenser. It sits under you points, comes out through a rubber bung in the side of the dizzy. It's (I think) $10 genuine from Nissan. Definitely go genuine, I've tried the aftermarket one, it didn't fix my idle issue, then after changing almost the entire ignition system and rebuilding carby, put the genuine condenser in and that fixed it.


Sent from my iPhone using Motorculture mobile app

[mahse]

Well here's an update,,
New condenser, new points, new plugs (all genuine nis) points set to .5
Now coil and ballast get red hot after 5 min driving, stall and won't start,
I put a cold wet rag over coil for 10 min and she off again, hopefully all the way home....
Does the non- extended rotor really do this or is it wirung to ballast?
Also new ballast, tried a few different coils, at wits end..

[mudnut]

G'day mahse. I have looked at the wiring diagram. If it is a 12 volt system, the red wire on the coil should have 12 volts on start up and should be reduced to run through a resistor when the engine is running. The resistor has a red wire and White/black wire, (I'm guessing that it is the ballast resistor, but I could be wrong). I have been told the resistor is fitted to stop the coil from overheating. With the ignition on, (engine not running) there should be about 10.5 volts across the points. With ignition off, remove the two wires from the coil and the high voltage lead. Using a multimeter set to OHMS the resistance between the terminals should be 1.08 ohms to 1.32 ohms. The resistance between the High tension lead and the positive terminal should be 9000 ohms to 13400 ohms. Point gap is .45 to .55mm. Dwell angle 34 to 40 degrees. The condenser is just a capacitor. I used to check them (ignition off) by disconnecting the lead and touch it to earth momentarily (discharge it). With the multimeter set to Ohms and the test leads across the lead and earth it should read infinite ohms. I would then set the meter to milliamps and touch the test leads across the earth and the terminal. You should get a tiny surge of milliamps. This test works better with a moving coil or anologue meter.

[ctaylor58]

Maybe try a better type of fluid over vacuum lines and inlet manifold to find vacuum leak if there is one present. Good luck