crwys

I know replacing the knock sensors seems like a lot of work, but that is most likely your problem. I had the same symptoms., code only appeared after 2500 rpms.
I bought a 2 densos on ebay for cheap. Replacing the harness and the coolant bypass hose cause its cheap, at the bare minimum. There a few other things you can replace while doing this job too.

dajain

Haha, getting to the knock sensors doesn't look like a bad job at all. I'm not intimidated about tearing into the motor to replace a part that is needed to be replaced.

I have seen that the knock sensors are a pretty common fail on these cars thru a lot of research and what people have said. But on the other token, the same research has also pointed to the VVT solenoids also being a common failing part on these cars. Also the shift console, coolant temp sensor and many other parts that "could" be the issue with this shifting problem.

BUT, (there is always a but) in all my research, I have yet to find a diagnostic troubleshooting sequence for a person to find out what has failed and what hasn't. All I have heard (from several places, not just here) is change this part, change that part, this is what fixed my car, my buddy did this, etc. and no one has offered a troubleshooting sequence. As I said, there are several parts that can cause this issue with the shifting.

So, what I am hearing (from several places) is that people just throw parts at these Lexus's until they get the correct one changed to fix their problem or they just reset the computer by disconnecting the battery, knowing the code is going to show up again. No one has offered ANY diagnostic procedure to pin point the root cause of the issue. Just a lot of "most likely's", "probably's" and "maybe's" in the suggestions on how to fix the car. No "here is the troubleshooting sequence for that code" scenario.

I have no doubt this forum has a lot of knowledge about these cars, but apparently I am asking for too much. Again, I am not going to start throwing parts at this car. It's not a real valuable Lexus but that doesn't mean I wouldn't mind getting it fixed.

I really do appreciate the responses and input. Thank you guys again! I'm not angry, upset or anything like that and I'm not putting anyone down at all. I've been on enough forums and know how things can be taken the wrong way and conversations can get out of hand. Just looking for a real troubleshooting sequence to get to the root cause of the problem without spending $100's more than I need to get it running right. If that can't happen, then I will part the car out and call it a day.

crwys

lexus2000 gave you a pretty good explanation for testing the knock sensors but like he said, the car's computer does this for you. If it throws a code specifying the knock sensor, it most likely is.
you say you dont want to throw parts at the car but you are replacing the oil control valves correct? Most people try to replace other things first because they are easier or cheaper than the knock sensors which is why I mention it.
Yes the oil control valves are a common problem when these cars get into higher mileage. But they arent known for throwing a knock sensor code. It's a random misfire, misfire on 1, 3, 5 code or misfire on 2, 4, 6 code. Sometimes they will also throw a code directly pointing at the oil control valve.
The shift problem is a certain group of fault codes found by the computer that may cause harm to the engine. So for example if you get a catalytic converter code, evap system code or system too lean code, ect. You will still shift fine. But if you are getting a confirmed misfire code, transmission code, knock sensor codes, ect. You will not shift past 3rd to protect the engine.

dajain

And of you look at the other responses and from what I have heard from several other forums and people is that when it is the knock sensor, most time it is intermittent. Reset the codes and drive until the light comes on again is what I have been told on many instances. And yes, Lexus2000 did give a good description on testing the knock sensors but, unlike what was said about them being expensive, they are only $140 for the pair of Denso's. So, the time to fix and the price of the parts is not a disconcerting factor either.

With the car, I reset the codes and it immediately comes back after being run. Resetting the codes and waiting for the light to come back on does not work in this case. When you do drive the car, the power is lacking under hard acceleration, up hills, and even off a stand still. A faulty knock sensor would not cause a lack of power under these circumstances. In fact, faulty timing advance would and in turn would cause a knock in the engine which would also cause the knock sensor code. Another thing the car does is decels pretty hard, even at a lower rpm such as 2500. This could also be a timing issue also but it may be just the computer controlling the engine in limp mode. But, yes, it should be throwing a code for the solenoids but it isn't. The car is doing several things that are a common symptoms of incorrect timing. I am not just throwing parts at it, I am working off my experience and what the car is acting like.

Ironic thing about all this is no one has asked if the car is acting wrong or even asked how it drives. No one has even asked how many miles it has on it. It was even said that these VVT's are a common problem with the higher mileage vehicles, but no one has asked how many miles are on it. haha. I do know (which I said earlier) that maintenance was probably neglected by the previous owner. These solenoids require clean oil to operate properly. Yes, they are easier than the knock sensors to change, but that is not why I'm doing them first. The car is acting in such a manner that has me convinced the timing is having issues.

So, my next step is to change the oil (full synthetic 5w30) & filter (Denso), install the new VVT solenoids (Denso), and go from there. I already have the parts here and should be able to get to it in the next day or 2. Thanks for the replies guys!

crwys

Hmmm well the only thing I can mention is when i was having problems with my knock sensors, sometimes the car would get stuck in 3rd or 4th gear causing acceleration problems and lack of power. So a faulty knock sensor can cause the symptoms you described. Also if you do and up replacing your knock sensors, make sure you replace the wiring harness, coolant bypass hose, and use Denso knock sensors only and consider replacing your fuel injectors, bank one coils, spark plugs and intake gasket. The price of them really depends where you buy them from like anything else, if you buy the real deal Denso knock sensors, you are looking at $180 for one of them.
I do think if you are new to these cars you should be taking the advice we are giving you with a little more thought.
and also like I said when I had this problem my code would immediately come up again and it was indeed the knock sensors.
when you say several other forums? You must be referring to non lexus forums? I would limit you research to Lexus forums only.
hope you get it figured out soon

dajain

No disrespect at all by saying this so please don't take it wrong. But, again, the knock sensor was an intermittent issue with your car. You say "sometimes" it would happen. That is not the case with this car. There is a real problem with the car as it throws the code with every drive. Is it that hard to believe that the knock sensor circuit could actually be working properly and there is something else wrong?

We will see once I get the solenoids in and the oil changed.

crwys

no as I have said twice now, it was not intermittent. I would clear the code as I was driving, once I came to a stop and got up to 2500 rpms again. The code would appear immediately.

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dajain

^^^^^ "Sometime" and I quote. ^^^^^^ But anyways.

crwys

.... lol. I'm sorry I'm typing on my phone but maybe that sentence didn't make sense?

Hmmm well the only thing I can mention is when i was having problems with my knock sensors, sometimes the car would get stuck in 3rd or 4th gear causing acceleration (Theres a comma after sensors, sometimes is referring to the car would get suck in 3rd of 4th gear )
SOMETIMES, the car would get stuck in 3rd of 4th gear.
Not "sometimes, my knock sensor code will pop up"
Not "I was having problems with my knock sensors sometimes"

My knock sensor code was always there. Not sure where the confusion is here.


Again just trying to help you by telling you, I had the same exact symptoms you are describing it sounds like and it was indeed my knock sensors.

dajain

The Knock sensor on this car only pops up at hwy speeds. The car never goes into 4th gear. So that is a different scenario than what you experienced with your car. There is your confusion.
This car goes smoothly from 1st gear to 3rd gear. Never gets stuck in any gear.

What you experienced and are describing with your car is different that what this car is doing. THERE IS YOUR CONFUSION.

crwys

Well like I said, it sometimes would only get stuck in gear, and I drove with this code for over a year. You just started experiencing this problem. So it is possible for you to run into the same problem. But regardless the symptoms are pretty much the same because my code was still immediately coming on, not interminnitely. Thats where you were confused at because you misread my sentence.
You claimed that I said my code came on interminnitely but you now realize that you mis read my sentence and you were wrong. So now you are upset.
yes the code pretty much only comes on at highway speeds because that's when you will hit 2500 rpms upon accelerating and not shifting past 3rd.
We are all here trying to give you advice which you are refusing to take into consideration, so why even come to a forum at all?
good luck and have a nice day.

dajain

Update:
Please read carefully, ALL steps!

1. Changed engine oil
2. Installed new solenoids
3. Started car and let it warm up
4. Started driving on Hwy
A. Shifted thru all 4 gears smoothly
B. No engine codes popped up
5. Got 2 miles down the road and turned around
6. Started driving at Hwy speeds again
A. No shift into 4th
B. No check engine light
7. Stopped, checked for engine codes = NONE
8. Turned off VSC = No change
A. No 4th gear
B. No engine codes.
9. Turned VSC back on = no change
10. Checked for codes = None
11. Turned O/D off = 3rd gear as expected
A. Dash light comes on
12. Turned O/D on = Still no 4th gear
B. Dash light goes off
11.. Drove back and forth 3 times, 2 miles in each direction
A. tried different scenarios on each pass = no change
12. Got back to the house and checked for codes.
A. No codes were present
B. Check engine light NEVER came on

Conclusion, The engine wasn't advancing (causing the knock code) as I stated before. Timing is advancing now which equals no more knock. Shifting into 4th is still intermittent with no codes. Motor is ALOT more responsive and aggressive when given throttle and pulls a hill better also.

Still think it's the knock sensor?

Any ideas what else can cause an intermittent shifting issue WITHOUT setting any codes? When it does shift into 4th, it is a smooth shift and pulls strong. Doesn't seem to be a transmission issue.

crwys

The knock sensor? 🤣😂🤣😂😅

dajain

no See, now that is funny. You don't want to admit that the solenoids corrected the knock sensor code and are being persistent that the KS is still at fault when there is no KS code.
If the KS was at fault for the check engine light, it would still be triggered no matter what I did with the solenoids.
The knock sensor is starting to sound like a real "cookie cutter" response here.
You were wrong about the solenoids having anything to do with the KS code and I just proved that wrong. I think I'm done here.
Have a great day.

RXGS

iTrader: (2)

I mean knock sensor is the cookie cutter response because given the facts you gave, its often (not always) the correct response. Historically, the patterned failures of these cars occur almost like clockwork. I'd suggest parting the car out at this point as you only paid $300 for it and seem to be pretty determined that its a more serious issue, and you'd know better than anyone else reading on the forums. I know that reads as sarcastic, but its not, because if its a wiring problem it could cost a lot to fix.

I think it goes without saying that most people on here aren't mechanics, and may not be even mechanically inclined, but when your symptoms replicate some, if not all of the symptoms that we have had, and we fixed the problem with a typical fix, its hard for us non-mechanically inclined people to not suggest the typical fix.

Maybe try toyotanation, those people seem to be more like mechanics than the people here who are simply people who happen to own the car.