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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 · #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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Discussion Starter · #14 ·
Currently at 230345 mi, with not much to report.

I had only one cold start, I thought I heard it knock for < 1 sec and then it idled normally. Nothing serious this far so it will continue to be monitored.
 

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Currently at 230345 mi, with not much to report.

I had only one cold start, I thought I heard it knock for < 1 sec and then it idled normally. Nothing serious this far so it will continue to be monitored.
Was the egr cooler clogged? Could you see light thru the one you pulled from your car?
 

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Discussion Starter · #16 ·
Yes, no visibility as-found. I poured liquid into the intake manifold end (exhaust side down) and it would only drain from one side.

It was extremely difficult to clean. After 3-4 days of soaking it in purple power degreaser, which was efficacious on the EGR intake manifold inlet tube, I could only get it 25% cleaned. It didn’t work as well for this component because there was no way to physically agitate.
 

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Discussion Starter · #17 ·
Current mileage: 238074 mi
Update: Still no major symptoms to be concerned about. There may be another issue with the symptom of misfire while the under light throttle transition from ICE on to electric as if the engine can’t decide whether it wants to be on or off, or maybe the engine keeps running longer than it should but in a half arsed way.
 

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I appreciate that you keep coming back to update. This thread is a great resource [that I bookmarked a while back] and keep coming back to, as I go through all my preventative maintenance tasks. Fortunately, I'm not yet at the point where I need to start thinking about a pre-emptive HG replacement, but I am at the time frame where I'm replacing a lot of the assemblies that can fail with age, potentially leading to such a failure (~115k mi). I did the EGR stuff back at 108k, including the throttle body and intake manifold, along with the plugs, the trans fluid, the PCV replacement, and the install of a catch can . Next on my list is addressing the coolants, the thermostat, and water pumps, to which I just sprung for the OEM / Aisin replacements, along with some new Denso coils. I'll probably replace the intake at some point with the newer model as well, but I'm gonna see if I can get Lexus to give it to me first, since the early design was so terrible.

I checked back in to the thread today, as I've been building out a part number and DIY resource document for the vehicle as I go through my to-do list, so your list of parts was quite valuable in saving me a bunch of time for the HG section.

I'm familiar with head bolt removal/torquing procedures and I've replaced timing belts in the past that required near full teardowns, so I'm not too worried about tackling the HG job myself eventually, but is there any particualr step that you found especially difficult or would caution others about, before they get to it?
 

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Discussion Starter · #19 ·
Cowl does not have to be removed.

Leave the exhaust manifold attached to the cylinder head. Disconnect the two spring bolts and replace the exhaust donut gasket. It’s easier and less risky. Manifold also serves as a handle to pull the cylinder head off the block.

1/2” drive electric impact gun should be able to remove the crankshaft pulley bolt. I also had to impact it back on because I didn’t have the pulley holder tool at the time. I would recommend buying the holder tool if you have enough room to swing it because tightening fasteners with an impact tends to not be tight enough for high torque applications, but I never went back with the tool and it has 242400 miles now (18k miles since).

I left the lower EGR cooler stud/nut offwhen reinstalling. It took me 30 mins to remove that one bolt and I saved myself the trouble the next time.
 
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