A compression test will tell you which cylinder(s) have low compression (if any). There's a test called cylinder leakage, which is like a compression test with a PhD. It uses regulated air pressure on the cylinder to find where the compression is leaking to (rings, valves, cracks, head gasket).

Neither of the above will tell you if it's the valve guide seals.

There's a test for combustion products in the coolant, which is fairly cheap and easy to do, which will tell you if it's a head gasket or cracked head/block. You can buy the kit anywhere they sell Lisle tools. IIRC, it's about $50 or so for the kit, which is good for several tests.

My $ is still on the valve stem seals.

Agree with Fasteddie...I got 2 cents on it

Justice
Any good montero shop in So Cal?

TyTy,

Not that I'm aware of. I do all my own work, for better or worse. If I dont know how to fix it I learn and dive in. But thats just me. If you find a shop that knows DOHC Mitsu heads (ie 3000GT) you should be good.

valve stem seals i have the seals/vc gaskets and the tool to change them

mxmikie did you want to sell?

more smoke under load/acceleration is more than likely rings

more smoke at deceleration/coasting is more than likely valve stem seals

I think I disagree. Mine with bad rings smoked most under high vac. like on decel in gear from speed, but it smoked all the time. My leaking valve stem seals smoke most after prolonged idleing.

Bad rings will smell like burnt oil. Bad exhaust valve seals will smell like vaporized oil, like an oil spill on a hot exhaust manifold, since the oil doesn't enter the combustion chamber.

Under heavy accel, you won't see much smoke from leaking valve seals since the exhaust back pressure pushes against the leak. Alternating pressure pulses in the exhaust under idleing seems to pull the oil into the exhaust stream.

sorry to hijack this thread. but i have the same symptoms.
is your engine idling very rough? like it has a shot engine mount or misfiring horribly? so, far i have traced mine to a gummed up spark plug and maybe bad gas from prolonged storage.
so far no luck, i replaced the gas and spark plug. the truck still smoke (whitish). good luck to you.

tyty,

Is yours SOHC or DOHC? DOHC more labor intensive ($$$ shop repair) to fix, because more 'stuff' in the way to get to the valve stem seals.

Try:
Rally Sport Engineering, Costa Mea, CA (949) 548-0978
Owner: Paul Ludgate
He owns a Montero himself.
Former crew chief for various Suburau rally racing teams.
Website: http://www.mitsubishirepair.net/

Good luck !!!