Possible vacuum leak 2000 Rx300
07-18-21 | 03:04 PM
#16
Pit Crew
Joined: May 2018
Posts: 146
Likes: 5
From: OKLAHOMA
Everything I know specifically under the hood of an RX came from this forum. I’m a chemical engineer, which means I can design an engine but suck at fixing them. Keep that in mind 😝
Ok is this correct?
- You aren’t getting a code for lean air:fuel mixture, so there may be another vacuum leak but the car seems to be able to adjust, because the leak is small and/or the car is compensating by keeping the injectors open longer to add more fuel. more on that in a minute. btw this (air leak and p0440 code w/ lean mixture code p0174) is the problem I am currently trying to correct.
- You have knocking but are only getting a KS sensor code on one bank.
- Higher octane at least partly alleviates the knock.
- The car struggles under load.
Follow up Q - what mileage are you getting? Any other codes been thrown since this started?
An educated guess is that only one bank is actively adjusting ignition timing, while the other is in some fixed/limp mode. One bank is knocking, the other isn’t, and the two banks are fighting each other. Perhaps also, due to the vac leak you’re already at the top end of fuel delivery per stroke, so the car can’t get enough fuel under load which combined with partial knocking the engine boggs down. If that guess is correct it still comes back to the knock sensor needing replaced.
Ok is this correct?
- You aren’t getting a code for lean air:fuel mixture, so there may be another vacuum leak but the car seems to be able to adjust, because the leak is small and/or the car is compensating by keeping the injectors open longer to add more fuel. more on that in a minute. btw this (air leak and p0440 code w/ lean mixture code p0174) is the problem I am currently trying to correct.
- You have knocking but are only getting a KS sensor code on one bank.
- Higher octane at least partly alleviates the knock.
- The car struggles under load.
Follow up Q - what mileage are you getting? Any other codes been thrown since this started?
An educated guess is that only one bank is actively adjusting ignition timing, while the other is in some fixed/limp mode. One bank is knocking, the other isn’t, and the two banks are fighting each other. Perhaps also, due to the vac leak you’re already at the top end of fuel delivery per stroke, so the car can’t get enough fuel under load which combined with partial knocking the engine boggs down. If that guess is correct it still comes back to the knock sensor needing replaced.
07-18-21 | 03:07 PM
#17
Pit Crew
Joined: May 2018
Posts: 146
Likes: 5
From: OKLAHOMA
Posted the above then thought of the VVT solenoids, I wonder if a faulty VVT solenoid on one bank could cause knocking, since those solenoids impact valve timing which also impacts compression ratio Checking this is relatively easy by swapping the vvt solenoids and see if the codes switch with it, and vvt solenoids are cheaper and easier than a knock sensor.
I wonder that too, maybe all the seafoam i have done has got something lodged in one, i guess i could pull just that bank and take a look, but i did replace them when i first got he vehicle with denos's.
07-18-21 | 05:33 PM
#18
Pit Crew
Joined: May 2018
Posts: 146
Likes: 5
From: OKLAHOMA
SO, just took out bank 2 VVT and fliter, both looked brand new almost, cleaned em anyway with carb cleaner, put back togeather, snapped bolt that holds in VVT selenoid, gonna have to drill it out, looks like a zip tie will do for now lol.
Would anyone happen to know the size of this bolt? thread and all that?
Would anyone happen to know the size of this bolt? thread and all that?
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Androman (07-19-21)
07-19-21 | 02:13 PM
#20
Pit Crew
Joined: Jul 2016
Posts: 199
Likes: 43
From: IN
Originally Posted by Androman;[url=tel:11089336
11089336[/url]]SO, just took out bank 2 VVT and fliter, both looked brand new almost, cleaned em anyway with carb cleaner, put back togeather, snapped bolt that holds in VVT selenoid, gonna have to drill it out, looks like a zip tie will do for now lol.
Would anyone happen to know the size of this bolt? thread and all that?
Would anyone happen to know the size of this bolt? thread and all that?
07-19-21 | 02:48 PM
#21
Pit Crew
Joined: Jul 2016
Posts: 199
Likes: 43
From: IN
Knocking causes
If you truly do have knocking, to the best of my knowledge each of the following can cause/contribute to knocking:
- Low octane fuel
- More air added per stroke eg by faulty VVT solenoids
- Reduced volume per stroke eg by carbon deposits taking up piston volume
- Poor fuel atomization eg from clogged injectors
- Elevated engine temperature eg from a busted thermostat
Others may have a different list, but that’s what comes to mind.
Engine temp is easy with a temperature gun. I check by shooting the oil pan and it usually reads 200-210 or so. You can also check thermostat performance by removing it and dropping it in a pot of water on the stove. The thermostat should open just before the water boils.
Fuel injectors can be removed and shot with cleaner. There are videos.
Measuring stroke volune is not something I am familiar with but it should be possible by displacement if not direct measurement. Maybe there are vids or someone here knows of a method.
And I’m out of ideas.
- Low octane fuel
- More air added per stroke eg by faulty VVT solenoids
- Reduced volume per stroke eg by carbon deposits taking up piston volume
- Poor fuel atomization eg from clogged injectors
- Elevated engine temperature eg from a busted thermostat
Others may have a different list, but that’s what comes to mind.
Engine temp is easy with a temperature gun. I check by shooting the oil pan and it usually reads 200-210 or so. You can also check thermostat performance by removing it and dropping it in a pot of water on the stove. The thermostat should open just before the water boils.
Fuel injectors can be removed and shot with cleaner. There are videos.
Measuring stroke volune is not something I am familiar with but it should be possible by displacement if not direct measurement. Maybe there are vids or someone here knows of a method.
And I’m out of ideas.
Last edited by bordenj66; 07-19-21 at 02:52 PM.
02-04-24 | 06:12 AM
#22
2nd gear
Joined: Feb 2024
Posts: 2
Likes: 0
From: AZ
My 2000 Rx300..... Sounds like a vacuum leak, rear drivers side. My fiancé took the seat out in the back and pulled the liner up and you can hear it but we can see a vacuum line or anything... it doesn’t like to take gas, I have to put it in really slow. Anyone know????
Did you ever figure this out I’m having the exact same issue with my Lexus RX 300 leak in the back and knock sensor code replaced sensors and oil control valve but I still hear a leak and codes are still kicking
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