12ht HJ61 Missing at 60k's

Hi Zilla
It could be alot of different things...i would start a cruisade yourself (which is only your time and some perseverance) and start with the basics and do a fuel filter change,(and cut open the cartridge to see whats in it...if there is green sludge, you have an algai problem and need to run some good fuel treatment.) air cleaner service, etc....the fact that it is doing this at part throttle suggests to me one of your injecters is partially blocked, giving a bad spray pattern and at part throttle, there is not enough fuel at the cylinder to burn like the rest.
Clean the fuel tank cap out of any dirt (2 screws pull it appart) and start using fuel treatment if you havnt already.
Be wary where you get your fuel from, pick a new servo with new tanks, where you see truckies filling up.... and stick to it.
Andrew

Zilla.
Its not your filter, it may be tapets or a broken top ring. Its unlikely to be the injector pump, it may be an injector. You can test the individual cylinders by loosening of the injector lines one at a time and note if the drop in peformance is the same for all.
Eric.

I've got a similar vehicle. Does it the problem persist at different loads on the same revs? Bad or dirty fuel can cause a lot of grief, as can water in the system - I have a water seperator fitted as well. If it is an import there can be problems with the way the japs adjust things - their fuel is worse than ours. A good dose of fuel cleaner doesn't hurt either. I use Redline additives to help keep the system clean. There are a lot of 'ifs' and 'maybes' here. All you can do is eliminate as much as possible before you have to take it in to a specialist.

An import eh? I'd be doing a compresion check as most have had 000's km wound off the speedo probably has cracked rings. sorry but worth checking.
Tour Boy

Hi Zilla,

I've got one of these two. Mine had done 90k when I bought it, now up around 105k.

Mine is not experiencing so much of a miss under load - in fact it pulls evenly, but when I put my hand near the exhaust pipe there is a miss that I would associate with valve problems if it were a petrol engine. Given everyone raves that these 12HT motors are 'the best Toyota ever made' the fact that several of us on this topic seem to have a similar problem, I'm thinking/hoping the rings/valve seats are probably okay on mine, and will probably try the injector route when I get brave enough to ask for an opinion.

Does it occur when you are at 1400rpm in any gear, or just 5th?

If it only occurs when the engine is hot, could it be a dreaded leaky head gasket? Any bubbles in radiator? Hard to start, losing fluid without apparent leaks? Petrol engines can be checked for leaky heads by a mechanic adding some magic indicating liquid into a test sample of the coolant. Apparently it tests for CO in the coolant, and it will pick up a trace without noticing any bubbles. I bought some magic copper based liquid sealant for my Ford 4l and it sealed it up. At around $15, it was worth a try and worked. Not sure if it would suit a diesel with the higher compression ratio.

I'm puzzled as to why you've got a gut feeling it's the governor in the pump. From a position of ignorance of diesels, I thought that would simply control the fuel flow to all cylinders. Not looking for your explanation, simply trying to be helpful with a different view.

Love to hear when you have a solution.

Regards,
Tim

These imports aren't a lot different to any other in that they need routine maintenance. That includes valve clearances, injector break pressures, fuel pumps, governors, compensators .... need I go on. If exhaust smoke isn't excessive, fuel consumption is OK and the engine runs smooth everywhere else then it points to fuel delivery problems. Finding someone you can trust to do it is the hard part. Owners automaticly assume diesel repairs = $$$$$$.
You can buy recon nozzles and get them fitted by any half decent mechanic ...... just make sure you get the correct nozzles. This is probably the next step before you got having fuel pumps pulled down.
Mine's just rolled 150K's. 9.5K/L highway 7K/L around town but smokes like a truck. Power is excellent, turbo well with in specs. For the sake of smoke I'm not prepared to pull the pump down, but I have had valve clearances adjusted.
There's lots of good info and opinions here on this topic. You just have to pick what's best for your bus.
All the best. Keep us posted.