Electrical problem needs solving b4 car goes bang again

Hi every one ,I have a 91 Gq ,manual 3.0 rb30 on petrol/gas.
My car every 50 to 100- ish km will miss on petrol or gas for a second and ignite raw fuel that i presume has been shot straight into the exhaust, then run fine,and generally a few minutes later will do it again then not for another 50 or 100 kms. In between this she seems perfectly in tune and does not miss a beat.This would not worry me so much if it had not blown the exhaust completely apart a week ago scaring the pants off me driving home from work. I asked a few people their advice which steers 2wards being electrical and have done a few things to the car but the problem is still there.
I have only had the beast a couple of months and dont know the history of it but here's what i have done so far...
New lpg converter and relay and solenoid
I had the exhaust replaced and new gaskets in exhaust pipe to manifold.
New leads
New gas plugs
Rotor looks good
New dizzy cap
Tune up
I have followed wiring away from back of coil plug and has a join in it so cut and rejoined and has made no difference.
I have not replaced electric points or coil as advice given to me had been that if they were the problem they should fail more often or pack up completely.
I want to fix this b4 i possibly blow the new exhaust , just don't want to give the car and a blank cheque to a sparky ,with the car only missing infrequently not sure of my chances of getting it fixed.
Any advice from you blokes would be a god send cause i dont really know what to do next :furious:
Cheers guys
Baz

Hi mate, have you tested the leads? one might be on its way out and shorting every once in a while......

Has anyone removed the distributor and checked for play on the shaft ?

I have put brand new leads on 2 weeks ago but cheers

o40ff i will remove dizzy and check for play in the shaft this arvo then .This has not been done.So there should be zero play in the shaft??

my old petrol puslux did that a few times. Turned out the wiring at the coil was a bit loose and would cause the ignition to sometimes turn off then on and make loud bangs. It was kinda funny cause we used to do this on purpose when i was a bit younger cause it sounded like a gun going off and used to scare the crap out of people. But yeah, check the ignition wiring around the coil.

Could be a sticking valve. Try some top end lube mixed with the oil.

I just found that my RB30 (carby) motor had an issue with the carby, the screws that hold the carby butter fly assembly to the body of the carby had worked loose. This resulted in the truck running rough and back firing. Idle was out on gas as well.

Im assuming you have a carby

To test pull your air cleaner off and grub the top of the carby and wriggle the carby - there should be no movement.

To fix, remove the four botten 12 mm bolts on the carby.

List the carby and tighten the screws.

While you have the carby off - do the heater mode - it wll give you more power.

Are you running a voltmeter watch for changes when it happens.
Intermittent electrical faults can be one of the worst things to find.
If it runs a resistored coil the resistors can fail.
I'd replace the condensor and disconnect the noise suppressor .
Check you don't have an overcharging alternator.
Check the ignition switch itself they can wear out and cause issues.
Personally i would fit a relay to the coil for a more reliable source puts less load on the switch.
Check all earths etc


also some lpg systems run an earth pulse saftey cut off to the negative side of the coil check that isn't shorting or faulty.
and keep an eye on the tacho if their is a negative side short the tacho will drop off as well.
I have even seen hidden cutout switches in cab connected to the tacho feed before .
and alarm systems with dodgy clip on connectors on the ignition wiring .