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Landcruiser Engine Dying While Vehicle is in Motion

Hi, folks! Got a problem that’s just eating at me and I can’t seem to figure out what the source of the problem is…it’s also eating up my wallet too!

I have a high-mileage 1984 Toyota Landcruiser that has the 2F engine, 6-cylinder, carburated. It’s also got a manual 4-speed transmission in it. I currently call him “Satan” thanks to 2 problems that I can’t for the life of me get figured out.

Problem 1: When I’m driving the vehicle down the road and the engine is at temp, it kills on me as soon as I push in the clutch and take the load off the engine. I’ll push in the clutch and start coasting to a stop and I’ll watch the tachometer go from 2500 rpms or so and drop to the idle range (900 rpm or so) and then it will just continue on down to zero as the engine kills. Fun fact: the engine doesn’t do this when it’s cold! Another fun fact: when I first bought the vehicle 6 months ago, it didn’t do this. I had to replace the power-steering pump right away, and in replacing it, my wrench slipped and snapped a vacuum valve. I drove it with no problems with the broken valve for a week or so before this issue started. Once it DID start, I quickly fixed the valve, and the problem has continued to get worse and worse and worse ever since then.

Problem 2: Since this thing lives off an excessively complicated vacuum system, I immediately suspected issues with the vacuum lines/valves. I went over each and every one of them, replacing old, worn, and cracked lines, and 2 bad valves. I also discovered (through my handy Haynes maintenance manual for the vehicle) that I had a HUGE vacuum leak in the form of a long metal vacuum tube that runs along the engine which was rusted completely through on one end. I sealed that up with JB Weld and let it cure…and ever since I sealed up that line, the damn thing won’t hardly run. It’s got NO power, it backfires, coughs, spits, and barely runs.

I had a compression check done and found low-compression in cylinders 3 & 6. I also notice a tiny little bit of coolant (antifreeze) leaking down the side of the engine block from up near the head gasket, and I’ve also noticed lots of steam/water vapor coming out the tailpipe, even when it’s up to temp. I’m beginning to think that I have a bad head-gasket. I’m also suspecting that it could be a bad fuel pump that’s cutting out…but it seems a bit beyond coincidence that it’s doing it every time I take the load off the engine when it’s warm!

I rebuilt the carburator, changed all the filters, did numerous repairs to the vacuum lines/valves, changed the thermostat (since that’s what powers the vacuum system), verified that the fuel pump is working, etc. No luck so far. I bought this thing for $2500 and am now around $4000 in it total…and I still don’t have a running truck. This freaking thing is already beyond what I could ever get for it for resale, so the thought of shelling out another $1000+ dollars for head-gasket or major engine repair/replacement is starting to make me a little sick to my stomach.

Any ideas? Your help would be GREATLY appreciated!

It sounds like that “long metal vacuum tube” might be part of the EGR system. EGR problems can wreak havoc with your idle. Where does it begin and where does it end? Doesn’t your Haynes manual identify what the part is? If “sealing” it caused the truck to have no power, that’s your starting point.
You also need to figure out what that broken valve is.
Can you explain how the thermostat controls the “vacuum system”