Hi from Arizona desert

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daveb602
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Hi from Arizona desert

Post by daveb602 »

This is my first post. Since I received my new PicoScope 4425A some days ago, I find it easy to use and rapidly gather gobs of data. It is considerably harder to interpret the data to identify problems from unique characteristics. I look forward to comparing my data to those in the waveform library.

My first application is to find the cause of a bad misfire and rough idle in a 2012 Toyota Camry Hybrid. The EV part seems to function great; the problem is the gas engine. Still the hybrid makes things somewhat different from many tutorials and posts on YouTube. I'll be interested to see how much hybrids are discussed in the forum.

Steve Smith
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Re: Hi from Arizona desert

Post by Steve Smith »

Hello and welcome to the forum, thank you for the post

We have an area of the forum dedicated to EV and HV applications here forum484.html

Re your Camry misfire, prior to attaching the scope how are your 4-Gas levels during rough idle?

Is the misfire present at idle or is this only present under load?

How is your serial data in terms of fault codes and relevant engine running parameters?

We can no doubt put those 4 channels to great use looking at:

1. Coil pack current flow (via the supply fuse to all COP units if applicable)

2. Crankshaft position sensor (to enable the graphing of crankshaft acceleration/deceleration)
The following links will help
viewtopic.php?p=100244#p100244
viewtopic.php?p=100694#p100694

To graph the frequency of your crankshaft signal use the "built in" math channels (You may have to edit if the rpm range is too small)
Image 1
Image 1
3. Ignition coil pack IGT signal (used as your synchronization signal)

4. Injector current flow via the supply fuse to all injectors if applicable.

The above will provide an overview of ignition and injection status during the misfire event but of course you can modify to suit the findings of your 4-Gas test and Serial data

I hope this helps, take care.....Steve

daveb602
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Re: Hi from Arizona desert

Post by daveb602 »

Steve, thank you for the information and suggestions on my Toyota Camry Hybrid (TCH), XLE, 2.5L, 2012 misfire. The misfire is noticeably present in three cases: 1) cold start, 2) upon ICE shutdown transition to EV while moving, and 3) under load such as heavy throttle to the floor going from 50 to 70mph.

The only OBD2 code now is P0301 for Cyl#1 misfire. Scanner Mode 6 also shows almost all the misfires counts on Cyl#1. Cold start usually generates 10-40 counts on Mode 6 Cyl#1. Goosing the throttle on the highway got 254 counts on Cyl#1. Occasionally Cyl#4 gets a few counts.

In-cylinder pressure data shows the biggest difference in cyl#1 from the other three cylinders. I’m hoping you can help explain why. In-Cylinder-Pressure is shown for Cyl#1 in Attachment 0, and Cyl#2 in Attachment 1. Cyl#3 andCyl#4 look very similar to Cyl#2. These are all taken cranking, but at least Cyl#1 looks about the same when idling. The hybrid cranks and idles at about 1000rpm. The intake vacuum pocket for all of them are different than the usual. Is this because this and many hybrids have an Atkinson cycle engine? Why would Cyl#1 likely be different and misfiring?

I have a lot more data including some per your suggestions, but I'd appreciate your comments on the above first. I'd also like to make sure I'm attaching files correctly.
Attachments
Toyota_Camry_2012_Petro_Cyl1_Cold_w_Mkr_8of32_Share_20210919-0002.psdata
Attachment 0
(848.79 KiB) Downloaded 20 times
Toyota_Camry_2012_Petrol_Cyl2_Cold_2or32_Mrks_20210919-0003.psdata
Attachment 1
(854.43 KiB) Downloaded 17 times

Steve Smith
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Re: Hi from Arizona desert

Post by Steve Smith »

Hello and thank you for the feedback

Focusing on nothing else other than the psdata files you have attached (thank you) I assume the engine was cranking off MG1 and the throttle was wide open?

I ask because of the reduced intake pocket you have highlighted?

A wide open throttle will result in minimal intake pocket depths to that we typically see of an engine at idle with the throttle closed (This also reflect on peak compression values too)

In the image below (Cyl 2) peak compression is displayed at 178 psi (How does this compare to spec?)
Our EVO event occurs at approx.152°ATDC ( of the compression stroke)
Our EVC we can approximate at 360° ATDC compression and IVO at 386.9° ATDC
Our peak negative pressure = -6.261 psi
Average cylinder pressure during the intake stroke = slight below 0 psi
Cyl 2
Cyl 2
Moving now to Cylinder 1 below
Cyl 1
Cyl 1
Peak compression is displayed at 132 psi (26% lower than cylinder 2)
Our EVO event occurs at approx.152°ATDC (of the compression stroke) same as Cyl 2
Our EVC we can approximate at later than 360° ATDC compression (approx. 366°ATDC) 6 degrees later than Cylinder 2
Our IVO at 408° ATDC approx. 42° degrees later than Cylinder 2
Our peak negative pressure = -7.9521 psi
Average cylinder pressure during the intake stroke = below -4.229 psi

We must tread carefully here to ensure we do not have a measurement error.
For example:

1. The zeroing of our transducer at atmospheric pressure
2. The intervention of VVT and Electronic throttle control

Whenever we think we have found problem we must first challenge our measurement technique and equipment

Assuming we do not have a measurement error, and the throttle is wide open during the testing of cylinder 1, why is cylinder 1 intake stroke pressure below atmospheric pressure (0 psi gauge)

This would most certainly reduce peak cylinder pressure as we can only compress the air we draw in and our cylinder 1 test results suggest there is a a negative pressure in the intake with the throttle wide open

Can we inspect inlet ports swirl valves and most importantly the valve lift of cylinder 1 inlet valves
This would include cam lobes, lifters and followers for wear and profile

I hope this helps, take care.....Steve

daveb602
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Re: Hi from Arizona desert

Post by daveb602 »

Steve, thank you very much for your cogent analysis and guidance. You have identified the problem with the Cyl#1 data; it was not at wide open throttle (WOT)! In fact, the Cyl#2 data was probably not WOT either. And by the time I got to these tests, the engine had cooled considerably also. You are very kind to explain what the data was telling us, both if it was and was not at WOT. That is very enlightening.

I don’t want to misled you. I am not a mechanic and didn’t realize that WOT is customary and would be expected. I’m a Toyota Camry Hybrid owner willing to buy good test equipment like the PicoScope, but reluctant to continually pay the dealer for inaccurate diagnosis and expensive repairs that do not solve the issue on a decade old car. I’ll admit that my basic problem in these TCH tests is ESO (Equipment Smarter than Operator).

I am rapidly learning how to operate the PicoScope, but TCH has a mind of its own. I read that cranking in-cylinder pressure tests should be performed at WOT, as you imply. Easier said than done with TCH. When driving it usually succumbs to my commands to accelerate, but in the garage just pushing the throttle is not enough -- the hybrid ICE usually just sits there idling or even shutting off into EV mode.

I put it into its "Maintenance Mode" (MM) and it is supposed to allow me to accelerate to 2500rpm even in Park. Sometimes it does. But, pull a spark plug and disconnect the fuel and ignition as for cranking in-cylinder pressure testing, then TCH throws numerous trouble codes, and refuses to open the throttle. Sometimes I have to clear codes just to get it to turn over at all. I tried leaving everything hooked up and just pulling one plug for a “Running compression test”. Without one cylinder it idles extremely rough, and still will not accelerate even in MM.

I understand that Toyota’s TechStream and some other scanners have a “Compression test mode” that slows MG1 down to 250 to 300rpm for these tests. I do not know if they also command WOT. I do not have such a scanner. Mine is BlueDriver which gives me access to lots of data, but does not send commands to the car beyond “clear codes”.

I also do not have a 4-gas exhaust analyzer.

Enough ranting about my personal problems. You have given me information I need to know to determine that Cyl#1 is no worse than the other cylinders. Attachment 3 is a different waveform segment of the same Cyl#1 data run I previously provided. This one has high compression peaks (168psi) and intake vacuum pocket similar to Cyl#2. I’m not sure of throttle position. Before your response, I did not know which waveform segment was most pertinent. I could have provided the whole string of data, but I don’t know if you and your IT system would get bogged down with 27MB files.
Toyota_Camry_2012_Petrol_20210919-0002_Cyl1_Cold_w_Mkr_27of32.psdata
Attachment 3
(854.65 KiB) Downloaded 15 times
Similarly, Attachment 4 is a different waveform segment of the same Cyl#2 data run I previously provided. This one has high compression peaks (180psi).
Toyota_Camry_2012_Petrol_20210919-0003_Cyl2_Cold_28of30_Mrks.psdata
Attachment 4
(854.28 KiB) Downloaded 16 times
From Chilton, the compression spec. is: Standard 160psi, Min 109psi, Difference 15psi. Using conventional dial pressure gauge Cyl#1 was higher than the others and all were much higher than spec.: Cyl#1 212psi, Cyl#2 201psi, Cyl#3 196psi, Cyl#4 200psi. Excellent especially after 72,000miles. Again, I did not pay attention to throttle; just default (closed?).

As you say “We must tread carefully here to ensure we do not have a measurement error. Whenever we think we have found problem we must first challenge our measurement technique and equipment… For example:

1. The zeroing of our transducer at atmospheric pressure
2. The intervention of VVT and Electronic throttle control”
… and ”swirl valves”

I am not using a Pico WPS500X. I have an SSI 500psi transducer; I made a custom scale and calibrated it using a vacuum pump, verified with comparison to readings from an air compressor, and a normal dial vacuum/pressure gauge per guidance from SIU Auto on YouTube. It seems to be accurate enough. But I have no idea what the TCH “VVT and Electronic throttle control” are doing; most certainly not WOT.

Based upon my Chilton it would appear TCH does not have “swirl valves” or flaps. Maybe they call it something else. I made pictures with a borescope through the EFI port that show two intake valves in the intake manifold, but no swirl valve or swirl flap is apparent. Incidentally, these borescope pictures show a lot of black carbon build up leading to one intake valve on Cyl#1 (and only that one cylinder). Does that help with the misfire diagnosis?

In a separate post I’ll get back to the crankcase position tests you recommended for further attention to the misfire problem.

Your analysis and comments do indeed help a lot. I really appreciate your help.

daveb602
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Joined: Mon Sep 20, 2021 2:46 am

Diagnosis Successful

Post by daveb602 »

Steve, thank you and Pico very much for providing the critical analysis and pivotal suggestion/question leading to the diagnosis of my TCH misfire problem. That question was: "Can we inspect inlet ports ... and most importantly the valve lift of cylinder 1 inlet valves".

To answer your question, I pulled the spark plugs again and took more borescope photos of all the valves as I hand cranked the engine. One of the Cyl#1 intake valves did not open at all! To confirm that was a problem -- duh -- and perhaps the only problem, I took pictures of all the other valves. Sure enough, all the others open in pairs.

Yuk. I thought I had a simple to fix misfire. Well it was fun learning how to use the PicoScope.
Attachments
2021-09-29-12-04-14-435.jpg

Steve Smith
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Re: Hi from Arizona desert

Post by Steve Smith »

Hello and thank you for feeding back and sharing the outcome of your diagnosis

It will be great to see the offending components if you are to dismantle the engine etc.

Given this is a valve lift issue, cylinder head removal may not be necessary, only the camshaft and lifters etc.

Assuming access permits of course!

Based on your diagnosis to date and the work carried out in the creation of a pressure transducer you may find yourself being head hunted by your local dealer.

This could be the start of something big for you in the form of "bring your problem cars to me"

Take care....Steve

daveb602
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Joined: Mon Sep 20, 2021 2:46 am

Re: Hi from Arizona desert

Post by daveb602 »

Find the “offending components” in the first three pictures?
Camshaft view
Camshaft view
Rocker arms
Rocker arms
Displaced rocker arm
Displaced rocker arm
The second intake valve rocker arm wasn’t where it was supposed to be. It was behind the spring pointing straight up never pushing the valve down. No wonder the Toyota Camry Hybrid (TCH) complained at cold startup and misfired sometimes. It was a true wonder that it still provided up to 40mpg on the highway; not so good in the city.

None of the parts appeared damaged, but since something made it slip out, I replaced both the rocker arm and the adjuster pivot.

I really did not want to pull the camshaft so I found a way to compress the spring and slip the rocker arm back into place without removing it. A conventional valve spring compressor would never fit. I cutoff an old wrench that fit over the rocker arm and fit under the cam with the lobe rotated enough for the wrench to just fit. I used old angle iron laying around to enable leverage for easy compression. It is way bigger than it needs to be, but I designed it to be adequate for one-time use with minimum cuts and holes drilled.


The last photo below shows the rocker arm in place ready for reassembly without ever removing the cam shaft.
Attachments
Finished rocker arms in place
Finished rocker arms in place
Compressor leverage
Compressor leverage
Wrench compressor
Wrench compressor

Steve Smith
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Re: Hi from Arizona desert

Post by Steve Smith »

Thank you so much for sharing and taking the time to feedback whilst including images as I know it can delay the repair process.

Nice improvisation of the valve spring compressor and as the saying goes "needs must when the Devil drives"

Regarding the dislodged rocker, miss-shifting and valve bounce may be one offender but this is near impossible in a "controlled" Hybrid with CVT

A possible sticking valve may be an offender too and perhaps worthy of further evaluation of the valve stems for "deposits" of tar/carbon etc.

Had there previously been a valve train rattle or intermittent misfires during the warm up process?

Great work and thank you again

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Grant_Baker
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Re: Hi from Arizona desert

Post by Grant_Baker »

I have seen this rocker fell off issue on a Lexus engine of similar year, similar engine design but V6. I did the same as you, replaced the rocker and hydraulic lifter. Did a leak down test, passed, same as a known good cylinder. Did a compression test, passed, same as another known good cylinder. Ran great for about 5-10 minutes til the valve warmed up. Then the (bent?) valve stuck in the guide and contacted the piston. Fun times.

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