perseuss69

There were quite a few leaks on both sides, interestingly. European salty winters make quick work of Japanese cars it seems. But they should be fixed for now and both O2 sensors read 0,9V at idle. I was hoping it would have some effect on the long term fuel trims as well, but no luck. I guess it's just due to weak compression or a mix of things.

Thanks! I'll be taking the car to a shop tomorrow and see if they spot anything.

Hi About a week ago I got a P0430 - Catalyst System Efficiency Below Threshold (Bank 2) code, that I cleared and hasn't come back. From what I understand that could be caused by: bad O2 sensor/s, cat failure, exhaust leak, and perhaps even from short trips during cold weather. Now, today, after some driving I had the car idling at operating temp and decided to take a look at the OBD2 readings, since it was idling a bit too high. I saw that one O2 was at 0,8V and the other at 0,1V. That seems odd. I've added a short video of the car idling and applying light throttle for a second. Any thoughts on what could cause this? Exhaust leak? Bad sensor/s? Also as a side note: the car is and has been for a long time, running quite rich. LTFT1 at -20% and LTFT2 at -10%. Thanks. Screen_Recording_20240109_180453_Torque.mp4

Removed the air inlet pipe just to try it, and the car sounds way better at higher revs. So now I'm wondering, are there any downsides to removing it? It's all before the air filter and MAF, so shouldn't affect much. Only thing I can possibly think of is sucking in hotter air since the intake hole is now nearer to the engine? Also thought I heard a strange windy noise when it wasn't really that windy outside. Not a constant sucking per se but intermittent blowing. I'm referring to part number 7 in the picture.

Yeah, I can't get that either. Matter of fact, I can't get anything that people normally use for that process, so I'm going to be using a 50/50 mix of acetone and ATF.

Bit of a halt of plans currently. Turns out that you cannot ship aerosol sprays out of the UK. Not sure what a good substitute would be that I could get my hands on. Don't think there are many.

In the first post in this thread I mentioned that I replaced the spark plugs and did a compression test, so I am aware of the process :). That's a good point to do two oil changes. I'll think about it. Will cost a bit more but it would be better.

Thanks for the advice. I am going to use the soaking method, to have any potential effect on the rings at all. That means removing the spark plugs, spraying/pouring some amount of Sea foam into the cylinder and letting it soak. I read on their site that you should let it soak for 2-3 days while adding a bit more each day and cranking the engine. Since it is indeed advised to change the oil after the procedure, I'm thinking of using Liqui Moly's engine flush as well. Or would that be too much?

@Mr Vlad @Linas.P What do you think, should I only soak cylinder 3 (lowest compression) with Sea foam or all of them?

Could you post an Amazon link for it? I can't find any Seafoam products on amazon.co.uk.

Actually, I might. Is Seafoam available in the UK?

I think I tried looking for it, but did not want to order it from the US and didn't find it in the EU. I cleaned my valves using K2 carb/intake cleaner. Seems like the way to go would be to let the pistons soak with Seafoam, but in that case I'd only do it with Seafoam, not some other brands. Other than that I'd use Liqui Moly's engine flush with my next oil change. I'm in Estonia.

I was looking for Seafoam, but it seems that you can only order it from the US, which is very expensive. The shipping alone was about $50 USD. I didn't find any European vendors for it.

Why'd you have the cleaning done?

It's a 2008 that I bought at 162k kilometers. That is not high mileage. The page I linked above says to make sure that the engine rpm should be above 250 to conduct the compression test. I'm fairly certain mine did not rev that high. So that might explain the lower compression readings overall, but it is still clear that one cylinder is way lower than the rest. Might try doing an engine flush with my next oil change. Perhaps I'll try getting a borescope to take a look at the cylinder walls. I use 98-octane fuel from a decent brand. At first glance it seems that Terraclean is a UK-based service? I'm from Eastern Europe.

I was checking live data one day, and something seemed strange to me. With the engine idling at operating temperature, bank 1 long term fuel trim stayed constant at about -4,8% and bank 2 at +7%.Why is one bank negative and the other positive? So far I've seen people talk about a leaking injector on one side, injector harnesses being swapped and AFR and 02 sensors connectors being swapped. Or just a bad O2 sensor. By being swapped I mean sensor 1 connected as sensor 2 for example. AFR sensor video (I create a vacuum leak at one point): Screen_Recording_20230914_101518_Torque.mp4 Fuel trim readings: Screen_Recording_20230914_143148_Torque.mp4

Which brand and which products did you use for the flush?

Coolant level is fine and has not moved whatsoever. Changed engine oil yesterday and it looked fine. Didn't see any glitter or water. The dry dipstick comment was made at 107k. It burns about a liter of oil per 3000km or so I think.

Fair enough. Car has 168k km right now. I've had it since 162k. Should have been a bigger red flag when at one point in the service history, there was a comment about the oil dipstick being completely dry. Might have to take a look with a borescope at some point.

Replaced spark plugs today on my IS250. Thought I may as well do a compression test. Turns out the compression is in a very bad state. According to this: https://workshop-manuals.com/lexus/is_250_awd/v6-2.5l_(4gr-fse)/engine_cooling_and_exhaust/engine/tune-up_and_engine_performance_checks/compression_check/system_information/specifications/page_3035/?expand_article=1 , the compression should be 14 bar or more, with a minimum of 10 bar. None of my cylinders got near that. cyl dry 8,5 wet 10 cyl dry 8,7 wet 9,8 cyl dry 7 wet 9 cyl dry 8,5 wet 9,7 cyl dry 8,5 wet 9,5 cyl dry 9,2 wet 10 Cylinder 3 is the worst, but none are good. Does anyone have any experience with something like seafoam? Don't think the car is valuable enough to replace piston rings. Also, not sure if this is relevant or not, but I checked fuel trims today while idling and engine at operating temperature. Bank 1 long term was at 7% and bank 2 long term was at -4,7%. Is this an issue? Could the two issues be related?

I did something dubbed as a "throttle body relearn procedure" today. Will see if or how long it lasts. Thanks for your input. I appreciate it.

Interesting. Thanks for the info!

Fair enough. The whole theory was that a sensor or something else might be a bit off but still in spec, so that there's no codes but still not working ideally.

I had diagnostics done and nothing seemed out of the ordinary. Only thing that stood out was that the suction control valve position did not change when the engine was revved in park. Not sure if that's how it's supposed to work? Another thing that maybe you could answer: when I put on cruise control at 100kph and the transmission shifts from 5th to 6th, the revs drop to 2k after the shift and then visibly drop to about 1900. What's that about?

The shop I took it to is extremely busy and well-regarded. I can't remember if they replaced the filter. I doubt they opened it up so probably just changed the trans oil. There haven't been any codes related to anything.