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What about the throttle position sensor or camshaft position sensor? Any thoughts on whether these items might be at play?
Who knows? But a throttle position sensor will usually have a dead spot in the resistor that can only be checked by a scope. When you reach that dead spot, the car will usually cut out. And a cam sensor generally effects the fuel injectors and it should throw a check engine light. The TPS sensor should throw a light too.
Harmonics causing some sympathetic vibration or noise that the knock sensor hears and thus alters the timing? Fresh oil would change the hydraulic environment the heads were operating in and miles would change the fluid properties - potentially enough to change the harmonic frequencies needed to affect the casting in the heads or echos in the various chambers in the casting...
Similar to the old Memorex commercial where the singer broke a glass or the soldiers marching over the bridge that created harmonic vibrations until it collapsed.
Just a WAG but might explain why it can't be diagnosed/found, why it fixes itself and why it's not very common.
Or ghosts. Ghosts will do that kind of stuff. They're cunning
Alright y'all - time to get geeky with me. I had some "good" hesitations today, and actually couldn't get them to go away this evening so I had trouble getting a good "baseline" run.
First chart from a couple days ago with no hesitation. Notice the ignition advance. I unfortunately didn't have pedal position data on that run, so we can't see how the pedal and throttle body angle corresponded.
Second chart from early today. It was rainy and cool today (can't blame ambient temps I guess). Again (like yesterday), after parking for an hour or so, I came out and immediately had a big hesitation out of the parking lot. I had space, so I pulled to the right lane, came to a complete stop and had a second big hesitation.
Third chart is from this evening. The car say for maybe an hour again. I actually couldn't get a clean run this evening (I was hoping for a basis of comparison), so there are a number of big hesitations in this set. Of note to me were the ignition timing, and the fact that the engine computer doesn't tell the throttle body to stay in synch with the accelerator pedal - I guess the ECU sometimes not only pulls timing, but also throttle angle! You'll see on the first run, the engine throttle over-shoots the pedal, and then on the next two runs, I get about half the throttle angle I ask for with the pedal!
All this said, the evidence does seem to support some of the engine controller / knock theories, but my diagnostic tool doesn't have the knock learned value parameter described in the TSIB, so I'm going to have to find a way to get it acting up and get Frank from Lexus in the car with his TechStream unit...
I was going to note that the commanded throttle position and the measured/actual throttle position seemed to match well, which makes me believe it's the ECU pulling back on the throttle angle or over-shooting the throttle angle based on its control logic (as opposed to some sort of malfunction in the throttle components or a dirty throttle body). I ran across this nice demo of the throttle control system and its basic malfunction controls.
I agree with the mechanics comments but he did not come to any conclusions why the condition occurs after an oil change only that he acknowledges it.
Well this is interesting revelation if there are in fact screens. I believe we as a community looked at various diagrams where the actuators go and found no evidence of the screens that are found in other Toyota engines.
One of you guys needs to find the location of the screens.
I was going to note that the commanded throttle position and the measured/actual throttle position seemed to match well, which makes me believe it's the ECU pulling back on the throttle angle or over-shooting the throttle angle based on its control logic (as opposed to some sort of malfunction in the throttle components or a dirty throttle body). I ran across this nice demo of the throttle control system and its basic malfunction controls.
Just a few thoughts. Based on your graphs we can rule out any major disconnect in the drive by wire throttle which is a good thing to eliminate any kind of ECU or traction control malfunction.
What we really need is to measure knock above all else. I have a feeling we cant always assume the presence of knock based on the retarding of timing or it's lack of advancement however if we might be able to detect a poorly functioning VVT actuator based on a jagged delayed ignition advance.
I've sent a note to the BlueDriver folks to see if I can monitor the knock value. Here is an interesting quote from the TSIB (that makes me think I need cylinder heads):
2. If the Knock Correct Learn Value drops from 17.0 CA to below 12.0 CA, and the IGN Advance goes to a negative degree value while duplicating the concern, continue to step 3.
If the values are comparable to a known good vehicle, the concern may NOT be related to this
bulletin — diagnose per the Technical Information System (TIS) depending upon symptoms.
I was able to prevent all hesitations today by keeping the rev's above 1500 during low throttle cruising and noted that the ignition advance never went negative except when it dropped sharply to smooth out the shift points.
Originally Posted by Devh
Just a few thoughts. Based on your graphs we can rule out any major disconnect in the drive by wire throttle which is a good thing to eliminate any kind of ECU or traction control malfunction.
What we really need is to measure knock above all else. I have a feeling we cant always assume the presence of knock based on the retarding of timing or it's lack of advancement however if we might be able to detect a poorly functioning VVT actuator based on a jagged delayed ignition advance.
I've sent a note to the BlueDriver folks to see if I can monitor the knock value. Here is an interesting quote from the TSIB (that makes me think I need cylinder heads):
2. If the Knock Correct Learn Value drops from 17.0 CA to below 12.0 CA, and the IGN Advance goes to a negative degree value while duplicating the concern, continue to step 3.
If the values are comparable to a known good vehicle, the concern may NOT be related to this
bulletin — diagnose per the Technical Information System (TIS) depending upon symptoms.
I was able to prevent all hesitations today by keeping the rev's above 1500 during low throttle cruising and noted that the ignition advance never went negative except when it dropped sharply to smooth out the shift points.
No luck on monitoring the knock value. They said it's just not supported (apparently it's not a standard OBDII value)
On a positive note, I am fairly confident I have been preventing the recurrence of the hesitation by preventing the engine from 'lugging' at RPMs under 1500 while cruising. I'm guessing it's those operating conditions that cause the undesirable resonance that sets of the knock sensors.
I just use the manual gear selector to keep it in 4th gear under 30MPH, 5th under 40MPH, 6th under 50MPH, 7th under 60MPH, and 8th on the Freeway. It's becoming habit slowly but surely.
I've sent a note to the BlueDriver folks to see if I can monitor the knock value. Here is an interesting quote from the TSIB (that makes me think I need cylinder heads):
2. If the Knock Correct Learn Value drops from 17.0 CA to below 12.0 CA, and the IGN Advance goes to a negative degree value while duplicating the concern, continue to step 3. If the values are comparable to a known good vehicle, the concern may NOT be related to this
bulletin — diagnose per the Technical Information System (TIS) depending upon symptoms.
I was able to prevent all hesitations today by keeping the rev's above 1500 during low throttle cruising and noted that the ignition advance never went negative except when it dropped sharply to smooth out the shift points.
This makes me think that Toyota doesn't know for sure either and it's more of an ad lib then definitive.
I changed my Trans fluid 4 times and now use royal purple 5w30. I get well over 300 miles on 1/2 tank of gas. The motor feels like it has better compression. There is no hesitation. I don't have to "floor it" to pass. IMHO: Ditch the 5w20.
Some say 5w20 will actually shorten the life of your motor (research this on the net):
I changed my Trans fluid 4 times and now use royal purple 5w30. I get well over 300 miles on 1/2 tank of gas. The motor feels like it has better compression. There is no hesitation. I don't have to "floor it" to pass. IMHO: Ditch the 5w20.
Some say 5w20 will actually shorten the life of your motor (research this on the net):
You mean the engine oil? And I have talked to people that agree with your theory that 5w20 oil is an oil that is only used by manufacturers to increase fuel economy and some manufacturers have divided to go back to the heavier weight...I want to say ford did this in their trucks on the 5.4 engine at one point.
When I start reading about valve guides producing enough chatter to activate knock sensors, it does make me think to give a high quality 5w30 synthetic a try. I know I'm in the minority for saying that, but sometimes a heavier weight oil can do wonders with noise.
08-20-15, 05:21 PM
