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Discussion Starter · #1 · (Edited)
Subject: 2012 Lexus CT200h Premium Navi
Mileage: 228380 mi
Symptoms: Misfiring (knocking) progressively worsening from cold starts to all starts, misfire clears up after a few seconds of idling or throttle, CEL, coolant consumption of half reservoir per daily commute of 72 mi (but no leaks), and coolant in oil.


Current mileage on the CT200h is 228380 mi. I’ve been driving it for probably 3500 mi longer than I should after the motor began misfiring on every ICE startup, cold or warm, and then clear up after a few seconds. Coupled with the other symptom of coolant level dropping and after 1500 mi (of the 3500 mi), coolant contamination in the crankcase.

I’ve disassembled the top half and probably the most disturbing thing I saw was the amount of oil that accumulated in the intake manifold and back of the throttle plate. If I kept using the car, it probably would have clogged the elbow just under the throttle body altogether.

Enjoy the pics. Consistency is the same as a lightweight grease.







 

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Discussion Starter · #3 ·
PCV port in the intake manifold which ingests crankcase vapour from the PCV valve in the cylinder block. > 50% occlusion in the port and the hose was also significantly clogged.

 

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Discussion Starter · #4 · (Edited)
I cleaned the intake manifold by removing all control hardware then throwing it into a tub full of gasoline first to try to remove the hydrophobic gravy (as another user so aptly named it) and the carbon build up in the PCV and EGR ports. I followed it with a vat of purple power degreaser, then hosed it off making sure to force water out of the each of the 4 small EGR ports that meter the EGR gas into each intake runner.

I plugged the EGR holes of the more proximal runners to get the pressure to the last runner in the chain (corresponding to Cyl #1). It’s quite gratifying to see all the bit of hard carbon shoot out of each one.

Also did the same for the EGR intake tube, EGR port off the valve, and PCV hose. Didn’t get as many pics because it was messy.
 

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Discussion Starter · #5 ·
Pics of cylinder head off and original head gasket pics.

Coolant found in cylinder #1. Perforation through the rubberized layer of the head gasket observed at the cylinder sleeve between cylinders 1 and 2. Perforation on both top and bottom sides of head gasket, but worse on the bottom. Residue left over on the cylinder deck, at the site of perforation.

Deck surfaces of cylinder block and cylinder head were still flat to within 0.002” as-measured longitudinally and diagonally on the decks.









 

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Discussion Starter · #7 · (Edited)
In case anybody is curious,

Materials purchased/cost:
1. 04111-37315, (qty 1) Toyota Overhaul Gasket Kit which has everything from the oil filler cap gasket down to the valve stem seals, and even including the exhaust manifold donut gasket. $192.74
2010-2017 Toyota Overhaul Gasket Set 04111-37315 | Toyota Parts
2. 90910-A2011, (qty 10) Cylinder Head Bolts (no washers) $6.89 x 10 = $68.90
3. 90201-10344, (qty 10) Cylinder Head Bolt Washer $1.24 x 10 = $12.40
4. 90080-10291, (qty 2) Exhaust manifold-cat converter spring bolts $4.11 x 2 = $8.22
5. 13561-37020, (qty 1) Timing Chain Vibration Dampener $66.23
6. 13559-37010, (qty 1) Timing Chain Guide (Slipper) $27.27
7. 13549-37010, (qty 1) Lower Timing Chain Vibration Dampener $9.10
8. 13562-0T020, (qty 1), Timing Chain Upper Vibration Dampener $28.55
9. 13540-37030, (qty 1) Timing Chain Tensioner $24.29
10. 12204-37010, (qty 1) PCV Valve $5.18
11. 234-9112, (qty 1) Nippon Denso Primary UEGO Sensor $123.79
12. 00272-SLLC2, (qty 1) Toyota SLLC 50:50 per-mixed Coolant $20.38 / gal
13. Purified water $0.93 / gal
14. Engine Oil $23
15. 04152-YZZA6, (qty 1) Toyota Engine Oil Filter $3.17
16. 90430-12031, (qty 1) Toyota M12 Oil Drain Plug Crush Washer $0.64

Total: ~$602 + $25 S&H = ~ $627, not including a replacement EGR cooler, spark plugs, timing chain, engine air filter, lost hardware, or any hoses you may cut or replace along the way.
 

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Discussion Starter · #8 · (Edited)
Also needed 1 new spark plug. For some reason the cylinder 4 plug electrode was severely eroded, and I only saw it during re-assembly not during tear down. The plug gap was > 2mm, but it never misfired under load.

 

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Discussion Starter · #9 ·
Day 0 post-rehab: First start was as-hoped, no knock or other abnormal behaviours. Bled the air out of the cooling system. Left the plastic panels off and drove for 44 mi without any incident. Trying not to get too hopeful as some failures don’t always present day of repair.

Day 1 post-rehab: Drove another 50+ miles without incident. Re-installed plastic panels and in the process, broke another M6 fastener into the radiator support that will need to be drilled out. Other than that, seems well.
 

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Discussion Starter · #10 · (Edited)
Picture album if anybody cares to see pics without captions. If you haven’t opened up the motor before, it mostly will not be interesting.


Video of first start will be posted to YouTube after I edit out the parts of me in my pyjamas.
 

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Discussion Starter · #12 · (Edited)
Video of cold start from a couple days prior, with 288602 mi, because I drive a lot of miles.

Video from today of cold start. By this time, it’s been a week and current mileage is 228871 mi. Nothing else to report...other than I haven’t figured out how to rotate the video.
 

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Discussion Starter · #13 ·
Also, because cleaning the EGR was the most intensive part of the process, I’ve purchased a couple of spare EGR coolers that I will clean and test airflow so I can swap them out quickly the next time.

This is a better alternative to buying new at $300 or spending far too long to get it minimally clean when you need the car the next day or can’t have a lot of downtime.

If you’re local and are interested in an exchange feel free to message me.
 
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