1HDT Rough Idle

[AZlc44]

Hello Diesel Gurus, I’ve been on and off working on my HDJ80 Landcruiser trying to solve a rough idle issue. The truck has 260K miles on it. This spring I replaced the Injection pump and the injectors, along with the oil cooler, water pump, t belt and valve adjustment. I had the rough idle before all the work and still have it after, although the truck runs much smoother and gets much better mpg. No issues under load, no power issues, no mpg issues. White smoke that smells like diesel especially when it’s cold, and misfires much worse when cold. It seems like I’ve been able to narrow it down to cylinders 1 and 4 by cracking injector lines. Already did a compression test, numbers looked good and all within a reasonable amount of each other, did a combustion gas test on my radiator to rule out headgasket, reverified my IP timing (slightly advanced) also rechecked my valve clearances which look good. The shaking at idle is driving me crazy! Any help would be greatly appreciated. Thanks!

 

[Eurasiaoverland]

Have you checked the timing?

 

[Squash]

When it's a cold start issue most likely glow plugs.
Try at least two glow cycles before starting to see if it helps.
Otherwise test the glow plugs.
My HZJ75 loves 2 cycles, same kind of set up as the 1hdt.

 

[AZlc44]

When it's a cold start issue most likely glow plugs.
Try at least two glow cycles before starting to see if it helps.
Otherwise test the glow plugs.
My HZJ75 loves 2 cycles, same kind of set up as the 1hdt.

Actually my glow plugs aren’t functioning at all right now, I need a new timer. I was under the assumption the glow plugs weren’t triggered unless the temps were below 40F. Also, my issue continues even after the truck has warmed up, it’s just much more subtle. Do your glow plugs turn on even when temps are above 40F?

 

[AZlc44]

Have you checked the timing?

Yes, but I’m waiting on the Toyota SST. I timed it with an aftermarket tool, I will compare once it arrives, hopefully in the next few days. I am a bit far advanced though, and I also tried tuning it while running to see if I could get it to smooth out.

 

[OTBT]

Sounds like there might be a little bit of air in the lines, see if re-bleeding works - especially on the cylinders giving you problems.

 

[AZlc44]

Sounds like there might be a little bit of air in the lines, see if re-bleeding works - especially on the cylinders giving you problems.

Would the truck still idle rough even after driving around 100 miles? I’ve heard of air lock but I assumed that the air would be dislodged once the engine started running.

 

[duece71]

Have you tried the black hand pump on top of the fuel filter assembly? Does it move up and down or is it solid and doesn’t move?

 

[AZlc44]

Have you tried the black hand pump on top of the fuel filter assembly? Does it move up and down or is it solid and doesn’t move?

Was under the impression that it should be able to move when the truck is cold and not when the engines running. I’ll give it a shot and report back.

 

[AZlc44]

Updating this thread to help those in the future. Got my hands on the right adapter for my cooling system pressure tester. Cooling system holds 15 PSI no problem on a stone cold engine, but when starting the engine and idling it pressurizes to 15 psi in less than 5 minutes. Looks like the head gasket is blown even though it passed the combustion gas coolant test.

 

[Eurasiaoverland]

Hopefully you can get away with skimming the head and a new head gasket, though be prepared to need a new head.

 

[AZlc44]

Hopefully you can get away with skimming the head and a new head gasket, though be prepared to need a new head.

At this point, the engine has almost 500K Kms on it. It was a bit tired even before the HG let go. When I pull the head I also want someone to check the block with a straight edge, but that opens up a bunch of “while you’re in there” situations. If I can find one I may end up trying to source a short block and head and assembling from there.

 

[duece71]

Maybe worth a rebuild, 500,000 KMs is awesome.

 

[AZlc44]

Confirmed with boroscope head gasket is blown at cylinder 4. Cooling system holds pressure but the piston and cylinder are definitely steam cleaned. At least I got some cool pictures of my piston! Once again, never trust a combustion gas test.

 

[PBcuiser]

Were you noticing any coolant loss over time?

 

[AZlc44]

Were you noticing any coolant loss over time?

I did have coolant loss, but not a concerning amount, maybe an inch or two down in the overflow tank over time. At the time I had some leaks from the turbo coolant line so I chalked it up to that. I might’ve topped it up once in 2K miles. Compression test was also perfect, and radiator chemical test was negative as well. I would’ve never known without the boroscope. One of my intake valve clearances was way off, basically zero mm of clearance so I was sure that a shim would fix the misfire. When it didn’t I immediately knew something was wrong.

 

[PBcuiser]

I did have coolant loss, but not a concerning amount, maybe an inch or two down in the overflow tank over time. At the time I had some leaks from the turbo coolant line so I chalked it up to that. I might’ve topped it up once in 2K miles. Compression test was also perfect, and radiator chemical test was negative as well. I would’ve never known without the boroscope. One of my intake valve clearances was way off, basically zero mm of clearance so I was sure that a shim would fix the misfire. When it didn’t I immediately knew something was wrong.

Thanks super helpful to know some new things to watch for

 

[AZlc44]

Thanks super helpful to know some new things to watch for

One more thing, the radiator was always under pressure. Even when stone cold, after a week of sitting it still had pressure in the cooling system. Maybe not 15 psi, but at least 5 psi.