Outer Limits 4x4 Board

Hi, I was looking for some advice. I have a 93, hzj75 with a 400,000km's on it. It has developed a misfire when accelerating first thing in the morning (cold) and once it warms up it misfires under load from around 2400rpm and wont rev (under load) much more than 3000rpm due to the misfire. It will freely rev its head off when not under load. It has also devloped an intermittant buzz noise which sounds to come from the motor (left side maybe), but this comes and goes, it is hard to tell whether it buzz's when it is misfiring due to the road noise of the muddies and the other rattles etc that you would expect from a work ute that's had a hard life.

I replaced the injector pump a year or two back, but never got around to replacing the injectors. Filter hasn't been changed for 20,000km, but is due. I'm hoping it's filter or the injectors and not another expensive pump. Your thoughts please people.......

Start with the basics. Air filter, fuel filter, blocked pick up in the fuel tank?
Then injectors, then have fuel pump checked.

My TD42 was doing the same thing, they thought it was air but turned out to be dirt in the injectors.

I discovered if I primed the primer pump the buz noise from the injectors or pump went away. I changed the filter today and put in some injector cleaner, still surging but not as bad, me thinking maybe injectors?????. MIght even be two problems, air getting into the system (buzzing noise) and the surge because of the stuffed injectors. Still trial and error I guess, maybe someone has a crystal ball that tells all.

cheers

Thanks for the repsonse so far, it would appear that 'maverick93' may have been correct. New filter and one tank with injector cleaner and the problem is basically gone, still a little hesitation during acceleration, but can put up with it until I organise a set of injectors. I have regained a bit of faith in those engine additives.

they do that when the injector pump is worn out.usually light throttle about 2000rpm.