missfire gq 4.2 petrol

The problem I am having is that whenever I am driving, it has a random misfire! As it misfires the Tacho meter fluctuates, the needle quickly drops and returns as if the power is being cut and turned back on very quickly. this causes a back fire sometimes and makes it quite hard to drive. It can happen when the engine is hot or cold, under load/no load but seems the worst when I am coasting like slowing down for an intersection, that's when it flicks constantly!

SORRY I TOOK THIS FROM AN OTHER SITE as this is happening to my patrol

Hi mate, are you running LPG?

no just petrol

Ignition/injection problem on one of the cylinders?? Not much else I can offer - have you swapped out the plugs and leads??

Ok, could be a few things. what have you checked and can tick off as being ok?

Just throwing some ideas out there...

Hopefully someone else can throw some other things to check

• Check fuel filter to make sure It's not blocked
• Check spark, replace spark and if no success just keep spare spark anyway
• Timing?
• Check the points
• Check the coil

Just some basic checkovers but out of that list there's a good chance you'll find something there.

Yell out if you need help checking those or clarification, etc and let us know how you go.

check conections around balist and coil ensure the coil bracket on the coil is earthed properly and tight check for cracks in dizy cap

Hi,
As said above check all ignition and fuel, my GQ does the same thing about every 10,000-15,000klm, mine is running LPG, but normally easy to fix, quick change of points, sometimes only just need a quick rub with fine wet/dry sand paper. Reset timing and problem useually fixed. One of the things on my wish list is to replace cra*py points with petronics or some type of electronic ignition system. Hope you find the problem.

Mine was doing the same changed every thing (coil, leads, plugs, points,) and it still had the problem it ended up being the small earth wire inside the dizzy so I made up a new one and problem solved. hope this helps.

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Originally Posted by WHITEGQ

Hi,
As said above check all ignition and fuel, my GQ does the same thing about every 10,000-15,000klm, mine is running LPG, but normally easy to fix, quick change of points, sometimes only just need a quick rub with fine wet/dry sand paper. Reset timing and problem useually fixed. One of the things on my wish list is to replace cra*py points with petronics or some type of electronic ignition system. Hope you find the problem.

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I Have the Pertronix ignition and sometimes i wish it was points purely because there is no sure way of checking the module for problems a set of pionts you can turn the motor over and see the points are sparking no such luck with a module makes aa big differance in the bush between driving home and being towed home !!

If it still running a breaker point system? thats the first thing to be checked & it is also the cheapest at around $10.... Not hard to fit & im tipping its where the problem lie anyway.

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Originally Posted by sambar308

The problem I am having is that whenever I am driving, it has a random misfire! As it misfires the Tacho meter fluctuates, the needle quickly drops and returns as if the power is being cut and turned back on very quickly. this causes a back fire sometimes and makes it quite hard to drive. It can happen when the engine is hot or cold, under load/no load but seems the worst when I am coasting like slowing down for an intersection, that's when it flicks constantly!

SORRY I TOOK THIS FROM AN OTHER SITE as this is happening to my patrol

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Hey! I have an '88 Troll and you have just described to the letter the exact same problem problem I am having. Tested the leads yesterday and they came back well under the acceptable resistance, so ordered som new ones - they get here in the morning. I am trying to find out more info on setting point gap, as although they look brand new I want to be sure. Will let y'all know how I go...

Hey guy's a couple of other things to try if you have checked all the above and had no joy.

Try disconnecting the tacho wire at the negative side of the coil, (should be a yellow with black trace wire) also if the radio condenser (capacitor) is still connected to the coil try disconnecting this as well.

Hey everyone
I have read many probs todo with the TB42 miss firing, I myself have had the same prob.
I have changed from points to the petronix electronic ignition, I always had a small miss fire starting off from an intersection or lights etc, It got worse, so I changed everything from the leads to the coil to even the old Gas vaccum switch to a more modern electric shut off valve, still had the damn miss fire. I read somewhere on here to check the dissy shaft for sideways movement but all good in this department, BUT BUT I checked the movement of the electronic sensor in the distributor, and there be hold was a movement of about 3mm, the rivets that hold the sensor to the mounting base were not peened over that well, so I took out the sensor, peened over the rivets to give a more solid join and guess what?? NO MORE MISS FIRE!!! This was the only thing that I changed at this time, so my elimination process worked!
Has anyone else had this problem??
Hope this may help for future miss fires with electronic ignition...... It did for me

cheers
AJ

this is late I know, but having just purchsed a Pertronix I was amazed to find the rivets holding the black box loose on the base plate. I tightened before install. I told the supplier in Aus and they did not even acknowledge my email. Seems this is a common manufacturing faults based on other reports, and US made too!!

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Originally Posted by sambar308

The problem I am having is that whenever I am driving, it has a random misfire! As it misfires the Tacho meter fluctuates, the needle quickly drops and returns as if the power is being cut and turned back on very quickly. this causes a back fire sometimes and makes it quite hard to drive. It can happen when the engine is hot or cold, under load/no load but seems the worst when I am coasting like slowing down for an intersection, that's when it flicks constantly!

SORRY I TOOK THIS FROM AN OTHER SITE as this is happening to my patrol

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Hi Sambar Did you end up finding the fault as i have exactly the same problem and symptons thanks

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Originally Posted by minihall

Hi Sambar Did you end up finding the fault as i have exactly the same problem and symptons thanks

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Hi there minihall,

Welcome 2 the forum.

When you get a chance post up an intro about yourself and ur rig in the intro thread

Cheers

Todd

One part that everyone over looks is the condenser.
I have had the same problem with my 89 gq changed the
1 plugs
2 rotor button
3 points
4 condenser
Had no back fireing for 3 months now it is doing it under load.
Will be changeing leads & distribitor cap in the next few days.

Sounds like injection/sparkplug error leading to misfire on cylinder causing imbalance to me... try removing each plug individually and checking its function.

Hi mate.
Is it efi?.
If so have a look at " TPS" , throttle position sensor,
could be faulty and or bad earth some where in system.
If it's computer efi, then if like other nissans (car) you may be able to check dash light codes !.
If so, get a manual as don't have time to fully explain this on here.

Hope this helps

Hey mate I had the same problem with my GQ I found the wires from the dizzy jamed in my engine mount it would run good then the problem you are having would happen try checking all the wiring to your coil and dizzy hope this can help you.

I had a similar issue in my gq when it's was 4.2 carby .
It was the points not opening , cleaned them with emery paper , which fixed it .

Well the others have covered most of it all add on more, their is a covered spring atached to the carby at the back near the top whitch is your lean/ rich mixture lossen the three scrws and rotate the plastic cover. also might have water in the carby (hope not) strip down and clean...

well i hope you find the answer good luck

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Originally Posted by GQ88

Well the others have covered most of it all add on more, their is a covered spring atached to the carby at the back near the top whitch is your lean/ rich mixture lossen the three scrws and rotate the plastic cover. also might have water in the carby (hope not) strip down and clean...

well i hope you find the answer good luck

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hi GQ88,

im pretty sure hes sorted the problem out after 2 years haha.

just somthing we ask of our members on here mate. could you please head over to the introduction section and introduce yourself.

cheers mate

rusty