engine misfire under load

My 1992 4.2ltr petrol shorty patrol misfires under load.
This is most noticeable at 2000 to 2400 RPM in overdrive or whilst accelerating when towing without overdrive and continues right through to 4000 RPM.
The problem can be non evident upon cold start but becomes more apparent as the engine increases in temperature.
Occasionally the engine will back fire on LPG but the misfire problem is constant regardless of fuel type (LPG/Petrol).
The engine has done 180000 K's and the valve clearances are fine.
All advice is welcome.
Regards hillyandco

Have you got a spare pair of leads you could try first to see if thats the problem?

Sounds to me like an ignition fault. Could be spark plugs, leads, distributor cap or rotor button.

Tony

Welcome to the forum mate.

Please introduce yourself here when you get chance.

Like what GQ10 and YNOT said.

I would check your distributer for any corrosion, etc and signs of grey marks on the inside of the distributer cap.

If all thats still good, how old is your fuel filter?

Possibly just change your fuel filter whilst your there. It's cheap and you never know!

Let us know how you go too mate, It's good to hear feedback.

G/day mate & welcome to our band of sickly obsessed Patrol owners otherwise none as NISSANPATROL.com.au forum...lol

Whats your Rig mate Carby or EFI. this info will help.

Cheers
Paul

Hi Guys!

My rig is carby.
The fuel filter has just been replaced to no avail.

Ok this helps. Now tell me do you have a stock rotor button or have already upgraded to the after market extended one?

Cheers
Paul

The rotor button, dizzy cap, points, standard leads were all sourced from Bursons.
The capacitor Fuel filter and resistor were sourced from Nissan.

Ok... This is a common problem in the TB42s engines which is what your running. the course was a very large air gap between the rotor button & the distributor cap which usually results in miss firing. the after market extended rotor button will take care of this & you can get them from.

Extended rotor Button from Performance Ignition Services. 03 98723644
Price is $80, inc GST.

They do changeovers, at $35 plus $45 deposit.
Overnight freight is from $11 if required.


Also keep your dwell angle around 38 to 40 degrease this helps a lot as well.

Cheers
Paul

Thanks for the info mate.
As you might imagine, this misfire has been driving me insane for some time.
I will order the aftermarket rotor button immediately and keep you informed.
Regards John