Rough cold and "prefiring" on low.

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Joined
Apr 22, 2006
Threads
5
Messages
14
Location
South Australia
Hi all,

This is my first post here after buying my first LandCruiser. "Hoff" is 1986 fj62 with 330k and gas conversion. Only "major" thing that I had to do to the car was replace the radiator which was badly rusted. Car seemed to do really well for a couple of 2000 km trips.

Then one morning truck started missfiring. Not sure how to really explain the misfiring but I hear a loud bang from the engine and compression vanished for a fraction of a second. Took Hoff to Toyota and they tuned the engine and did compression test and found that 3rd cylinder had low compression (no figures), with possible burnt valve... I was also told of no vacuum to distributor, suspect hole in vacuum advance diaphram and carby needing overhaul. They put oil in #3 cylinder and car seemed to be fine, in fact better than ever before (probably because of being tuned), burning off all similar cruisers. I thought nothing of other stuff as truck worked well.

Then, during third big trip, the waterpump had to be changed. It had hole in it from no doubt the rust that got inside from the rusty radiator. After the waterpump was changed we drove another 500km and engine started similar type missfiring, maybe did it 5 times in total over teh 500km (like back-firing but but loud bang from front, so probably actually prefiring!?). Bangs were so loud that felt like they would do deffo some damage. When I looked under the hood, I could only spot air filter case lid open. Now back at city it has increased the misfiring. Today, when I was taking Hoff back to Toyota it did misfire 3 timer in row like a machinegun. At toyota they guessed that it is the 3rd, but would like to do flood test etc. first to get better idea. It does the firing always between 1000-1500 revs. Also, I dont get the loud bangs when I am on pertol, only on gas. On petrol it simply misses and jerks the car. When I cold start, I need to get it very warm before driving on petrol, less warm with gas. I dont drive on gas any more becaus bangs are very loud and sound damaging. And one more thing, it seems to also miss when I slow down with gear on.

Where do I start? Would like to start with the vacuum advance diaphram? Is that easy chance. How about carby overhaul? can I do that myself easily? Is it necessary? Or can you confirm my nightmare scenario of it definitely being valve problems?? I know many questions, but I would really try fix there problems before taking it back to Toyota...

Thanks for reading
 
I think you need to take Hoff out the desert and shoot him.:D
Seriously with 330 klm , a burnt valve ,malfunctioning distributor advance and a carb rebuild ahead it would be easier to look around for a good used motor or rebuild yours.
The backfiring is probably from the burnt valve allowing fuel vapour to escape and combust in the inlet manifold /exhaust system.This is not good.
Im guessing your in oz,if so a full rebuild starts at around $2250 and you remove/install.If your in WA I got a 3F in the shed with low comp that still runs ok:grinpimp:
Dont throw good money after bad taking it to toyota ,scrap it.
 
Huh, Thanks for you reply :)

So it wont make any difference that problem is on low revs when thaking off from standstill. And that it is only problem when running on LPGas?

Straight to scrap, is it? Even without making vacuums right?

Would anyone happen to know a good lc mechanic with experience of LPGas conversions in Adelaide. I might want second opinion just in case...

Cheers
 
hoffer said:
Huh, Thanks for you reply :)

So it wont make any difference that problem is on low revs when thaking off from standstill. And that it is only problem when running on LPGas?

Straight to scrap, is it? Even without making vacuums right?

Would anyone happen to know a good lc mechanic with experience of LPGas conversions in Adelaide. I might want second opinion just in case...

Cheers
My apologies if I sounded a little pessimistic but if an engine is backfiring and blowing the air filter apart probably because of a bad valve,trying to tune it will not be easy.

I think you need to find a good mechanic and get an honest appraisal if uncertain yourself.

Do you have a Gregorys manual for your landcruiser,they only cost about $29 and will help you with vac problem

I wouldnt want to see you scrap a servicable engine but I dont want to see someone pouring money into a mechanics pocket for an engine that is past it either.
 
No worries,

Its probably partly due not being able to let go in part of myself... Expecially after having been to Sydney and back and Port Lincoln and back (1000km from Adelaide) over the past 3 month without ANY problems... :crybaby:

Anyhow, I Picked up new vacuum advance on ebay for AUD55. I have got the manual and see if changing that will make any difference.

I probably would consider new engine too if the price is right (truck has got no on body). Where can I find a good engine thou? And how much would it cost?

Problem is mainly when its on gas, and given the petrol prices (about 3 times more expensive in Adelaide at the mo), would like to run on gas if possible.. To your knowledge does the engine manifest valve problem first with gas? I believe that the gas doe complicate(?) issues here and would like to maybe get a gas specialist to have a look too. Hello there anyone in Adelaide know a good mechanic with gas conversion experience?

Thanks for your reply
 
Gas doesn't lubricate like petrol, so there is a seperate lubrication system for the head. if that stops doing it's thing, you will end up with head troubles.

Also the timing is different for petrol than gas, so that should be checked.

I'd definately take it to a gas specialist. Toyota don't know s*** about gas. They just tell you not to run it.

Decent 2/3f motors can be found for under a thousand bucks (au) if it comes to that
 
Damn I sold a whole good distributor with leads for $20 last month.
Rove is right gas does cause more problems.
A friend has a 3 litre Patrol on gas/petrol with 400000klms and now it will only run on petrol.
I thought the LPG would have been easier for an engine with bad valves as it expands slower when it combusts.
As Rove says the timing is different ,you can go one way or the other depending on your preferred fuel.
The beauty of engine computers is they can be tuned to run on both perfectly.
Not many South Australians on here,try http://www.outerlimits4x4.com/PHP_Modules/phpBB2/ or http://www.4wdmonthly.com.au/forum/index.php
 
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