missfire gq 4.2 petrol

[Matrix]

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

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...

[Yendor]

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.

[AJNIVIUK]

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

[inter674]

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!!

[minihall]

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

[NissanGQ4.2]

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

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

[popup]

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.

[cycd]

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

[Robo]

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

[Dave1980]

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.