ivan129
BlownZX
Stuck Valve / Sticky Valve.
Hi 1UZer's. I thought that I would post this piece, as this is something that’s happened to me, and others I know with 1UZ’s.
The problem titled above, is common to many 1UZ engines after a few thousand miles.
The symptom is a misfire / loss of power, a pop / bang through the exhaust due to running lean on the affected cylinder/s
This has happened to me twice. The first time No.7, very back (LHS) exhaust valve was so badly seized in the valve guide that I had to remove the head to drive out the seized valve.
Second time, again, No. 7 back exhaust valve, was just slightly held open and the symptom were popping through the exhaust when driving. Thankfully I was able to free the valve by pouring some light grade oil into No.7 leaving the plug out and starting the engine with a rag held over the plug hole to catch oil being sprayed out. Oh, good idea to disable the spark from the affected cyl’s, while running too.
I would assume that this can also happen to other valves as well.
How to check for the problem? The easiest way is to do a comp test. Low comp on a cylinder is usually a sign of a valve seating problem. Generally, you’ll find that affected cylinders will be the rears and generally on the left (odd) bank.
Why does this Happen? 1UZ’s use metal valve guides and as they wear the clearance increases opening a window for corrosion to build up on the inner (Valve stem side) of the valve guide. Coupled with condensation that also tends to build up usually more on the odd bank (left side) of the engine always corrosion to form on metal parts under the cam covers. I have some old guides I pulled from heads sitting amongst bits in my junk draws where it’s evident to see the discoloration from rust inside the guide.
How can you avoid this from happening? Maybe! Engines that have not been run for a long period of time can often exhibit this problem, so regular starting will help provided the engine is brought up to operating temperature and best to drive the car. Regular oil changes with quality oil helps. When starting the engine always allow it to get up to operating temperature and drive it. Short starts and runs won’t allow the condensation to evaporate off and will start to contribute to causing this problem. Regular inspection and servicing of the PCV, removal and cleaning the cam covers may also help to reduce this problem from happening.
Can it be totally avoided? Yes, by fitting bronze or phosphor bronze valve guides to the heads, using quality, regular oil changes and ensuring you bring the engine up to operating temperate each time you start the engine.
Note: - All valves will build up carbon deposits on the valve head and stems under the guides. Those cylinders running rich or have an oiling problem due ring seal are always worse however my experience is that this usually doesn’t cause a valve to seize.
I hope other find this of use.
If you have experienced this sort of thing, please post your story.
Hi 1UZer's. I thought that I would post this piece, as this is something that’s happened to me, and others I know with 1UZ’s.
The problem titled above, is common to many 1UZ engines after a few thousand miles.
The symptom is a misfire / loss of power, a pop / bang through the exhaust due to running lean on the affected cylinder/s
This has happened to me twice. The first time No.7, very back (LHS) exhaust valve was so badly seized in the valve guide that I had to remove the head to drive out the seized valve.
Second time, again, No. 7 back exhaust valve, was just slightly held open and the symptom were popping through the exhaust when driving. Thankfully I was able to free the valve by pouring some light grade oil into No.7 leaving the plug out and starting the engine with a rag held over the plug hole to catch oil being sprayed out. Oh, good idea to disable the spark from the affected cyl’s, while running too.
I would assume that this can also happen to other valves as well.
How to check for the problem? The easiest way is to do a comp test. Low comp on a cylinder is usually a sign of a valve seating problem. Generally, you’ll find that affected cylinders will be the rears and generally on the left (odd) bank.
Why does this Happen? 1UZ’s use metal valve guides and as they wear the clearance increases opening a window for corrosion to build up on the inner (Valve stem side) of the valve guide. Coupled with condensation that also tends to build up usually more on the odd bank (left side) of the engine always corrosion to form on metal parts under the cam covers. I have some old guides I pulled from heads sitting amongst bits in my junk draws where it’s evident to see the discoloration from rust inside the guide.
How can you avoid this from happening? Maybe! Engines that have not been run for a long period of time can often exhibit this problem, so regular starting will help provided the engine is brought up to operating temperature and best to drive the car. Regular oil changes with quality oil helps. When starting the engine always allow it to get up to operating temperature and drive it. Short starts and runs won’t allow the condensation to evaporate off and will start to contribute to causing this problem. Regular inspection and servicing of the PCV, removal and cleaning the cam covers may also help to reduce this problem from happening.
Can it be totally avoided? Yes, by fitting bronze or phosphor bronze valve guides to the heads, using quality, regular oil changes and ensuring you bring the engine up to operating temperate each time you start the engine.
Note: - All valves will build up carbon deposits on the valve head and stems under the guides. Those cylinders running rich or have an oiling problem due ring seal are always worse however my experience is that this usually doesn’t cause a valve to seize.
I hope other find this of use.
If you have experienced this sort of thing, please post your story.
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