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High on Highlander
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Discussion Starter #1 (Edited)
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SOLVED: Per Toyota dealership, broken valve spring on cylinder #5. $5,400 repair estimate.

2014 Limited with 75k miles. Check engine light and Trac off lights come on, accompanied by rough engine and loss of power. Error codes indicate:

P0300 - misfire
P0301 - misfire in cylinder #1 (edited/added after obtaining freeze frame data since original post)
P0303 - misfire in cylinder #3
P0305 - misfire in cylinder #5

I know number of things can cause misfire, but main culprit is usually bad ignition coil on a spark plug. As luck would have it, spark parks #1, #3 and #5 are on the backside of the engine near the firewall. In other words, PITA to get to. Before I take apart the intake plenum, etc, I’m wondering what the real cause of the misfire is. It would be a huge coincidence for three coils to go bad at the same exact time. What could cause an entire bank to go bad? Oil in the spark plugs? Any ideas?
 

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Plugs or coil-overs are the most likely culprits. But that's awfully short mileage for the plugs or coils to be bad.


Is it happening a lot.


Before you spend the time getting to the back plugs, pull one of the front plugs. That might give you clue. Usually spark plugs wear out at close to the same rate.
 

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The P03xx codes are the beginning of the story. In addition there is wealth of data in the Freezeframe like fuel trim and the actual number of misfires per cylinder that were recorded that will help you understand where to start. It could be cam timing (OCV) - especially when you get more than one cylinder in the bank acting up.
 

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It could be cam timing (OCV)

Cam timing? How? Only way that can happen is if the chain jumps time. And it then would be happening all the time. It doesn't fix itself. It would need to be fixed.


It could be a cam sensor, but that would be a different error code.
 

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If this was my car the FIRST thing I would do is put a bottle of Techron in the tank and drive it at least 200 miles, then see what you have. Otherwise you COULD spend time and money and eventually find out the injectors were slightly out of balance due to the accumulation of deposits.

The first step in a diagnostic process is to eliminate the simplest possibility, it can't get any easier than pouring Chevron Techron in the tank and driving the car. I would not recommend any other injector cleaner, from personal experience I have seen Techron basically wake up virtually dead injectors in my own vehicles.
 

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Cam timing? How? Only way that can happen is if the chain jumps time. And it then would be happening all the time. It doesn't fix itself. It would need to be fixed.

It could be a cam sensor, but that would be a different error code.
Somebody needs to read up on computer controlled Variable Valve Timing (VVTi), and all of the problems that this system can induce when it skips a beat.

Attached is a page from the factory service manual on the 2GR-FE engine introducing the topic, as you don't sound familiar with how it works.

The system on the new 2GR-FKS can shift timing so dramatically (VVTi Wide) that it can cross the line between zones of the stroke, making the engine act like an Atkinson-like variable displacement mill. That would be like the timing chain jumping, oh, a half dozen teeth?

I had cam timing issues on my 2008 Sienna (same engine) and experienced occasional 2 or 3 cylinder on the same bank misfires, and only sometimes did I get a cam position code to go along with it. It is highly dependent on severity and duration. Again, the detailed freezeframe data tells far more than just a numeric Pxxxx code.
 

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High on Highlander
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Discussion Starter #8
Plugs or coil-overs are the most likely culprits. But that's awfully short mileage for the plugs or coils to be bad.


Is it happening a lot.


Before you spend the time getting to the back plugs, pull one of the front plugs. That might give you clue. Usually spark plugs wear out at close to the same rate.
Yes, it is happening consistently. Sometimes on idle, the engine will stall. Good idea to check one of the front plugs to see what's going on. Just unusual that 2 cylinders showing this code at the same time.
 

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High on Highlander
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Discussion Starter #9
If this was my car the FIRST thing I would do is put a bottle of Techron in the tank and drive it at least 200 miles, then see what you have. Otherwise you COULD spend time and money and eventually find out the injectors were slightly out of balance due to the accumulation of deposits.

The first step in a diagnostic process is to eliminate the simplest possibility, it can't get any easier than pouring Chevron Techron in the tank and driving the car. I would not recommend any other injector cleaner, from personal experience I have seen Techron basically wake up virtually dead injectors in my own vehicles.
Worth a try i guess, but I read elsewhere that driving with misfiring cylinders you risk messing up the catalytic convertor and other sensors.
 

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High on Highlander
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Discussion Starter #10
Somebody needs to read up on computer controlled Variable Valve Timing (VVTi), and all of the problems that this system can induce when it skips a beat.

Attached is a page from the factory service manual on the 2GR-FE engine introducing the topic, as you don't sound familiar with how it works.

The system on the new 2GR-FKS can shift timing so dramatically (VVTi Wide) that it can cross the line between zones of the stroke, making the engine act like an Atkinson-like variable displacement mill. That would be like the timing chain jumping, oh, a half dozen teeth?

I had cam timing issues on my 2008 Sienna (same engine) and experienced occasional 2 or 3 cylinder on the same bank misfires, and only sometimes did I get a cam position code to go along with it. It is highly dependent on severity and duration. Again, the detailed freezeframe data tells far more than just a numeric Pxxxx code.
I'm assuming AutoZone and the like don't provide freezframe data -- can I get this myself somehow or do I need to visit a shop? The misfire is persistent....after engine starts up, it's ok for a few seconds, then starts to misfire, run rough, low idle, occasional stalling. Again, the error codes are consistently pulling up P0303 and P0305....so 2 cylinders - which suggests to me there is something else other than a rouge spark plug or coil.
 

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Somebody needs to read up on computer controlled Variable Valve Timing (VVTi), and all of the problems that this system can induce when it skips a beat.

I have, and from what I've read a VVT error will be completely different errors.
 

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I have, and from what I've read a VVT error will be completely different errors.
The VVT oil control solenoids can fail with out setting a code. They can do this from dirty oil or, other reasons. I have removed them from engines, bench tested them and they showed to be good only to set misfires when re-installed. The fix was to replace it with a new part. There may be an updated version. Usually a bad oil control solenoid will cause misfires on all cylinders in whatever bank it is in.
Now, I am not saying that is the problem in this case. There are lots of things that can cause a misfire. Ignition, fuel, vacuum leaks, mechanical issues, just to name a few.
 

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sijaz...need full description on each DTC (diagnostic trouble code) IDK, just thinking code could list other reasons to cause misfire, not just splug. U can try goog for those codes? Good luck.
 

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I have, and from what I've read a VVT error will be completely different errors.
Then keep reading! You've now heard it from two of us. We don't know if this is the OP's situation, as we lack all the data required to go further. But any time I see more than one cylinders in the same bank throwing misfire codes at the same time, my experience with VVTi issues makes me add this to the list of possibilities.

I did keep some of that old data, so here's an example. Three cylinders in the same bank with different numbers of misfires. Sometimes one of them had so few it didn't register as a unique P030x code. Maybe the OP's situation. Sometimes we got a P0015 or the like (one of the 4 cams overly retarded or advanced), sometimes not. It depended on severity.

Sometimes we got the cam code alone, and zero misfires. Again, it all depends on how far out of phase, and the engine load at the time of the event.

BTW, I bought into the AutoEnginuity desktop PC system back in the serial port hardware days.
 

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If there's a problem with the VVT cylinder then you'll get an error code associated with it. These diagnostic systems are sophisticated. Yes advanced timing may cause a mis-fire, but if it won't generate a P0303 error code if there's a problem with the VVT unless the VVT is not sending a fault code (very unlikely, but possible).




Let's stick with the most likely causes first.


https://www.fixdapp.com/blog/p0303


https://dannysengineportal.com/variable-valve-timing-vvt-generic-obd-ii-fault-codes/
 

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High on Highlander
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Discussion Starter #16
If there's a problem with the VVT cylinder then you'll get an error code associated with it. These diagnostic systems are sophisticated. Yes advanced timing may cause a mis-fire, but if it won't generate a P0303 error code if there's a problem with the VVT unless the VVT is not sending a fault code (very unlikely, but possible).

Let's stick with the most likely causes first.

https://www.fixdapp.com/blog/p0303

https://dannysengineportal.com/variable-valve-timing-vvt-generic-obd-ii-fault-codes/
I tend to agree with you. However, the most common causes should result in just one or all three cylinders on a bank to generate a fault code. In this case, it is consistently cylinders #3 and #5. It’s puzzling why this would be the case. It would have been straightforward check if it were two cylinders in the front.
 

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In this case, it is consistently cylinders #3 and #5. It’s puzzling why this would be the case

I'm not totally ruling out a problem with the VVT, but it seems the least likely cause. I still think the most likely cause is spark-plug or coil-over.
 

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If there's a problem with the VVT cylinder then you'll get an error code associated with it.
We've already proven this not to be necessarily true. I provided hard data as captured by the OBD system, and you heard about it here from another member. It depends on the severity, whether the cam is running advanced or retarded, whether the pin is properly secured when it should be and releasing when it should, whether it's the intake or exhaust cam, engine load, how much the oil pressure as delivered by the OCVs fluctuates, etc. Heck, 24 hours ago you were talking about jumping timing chains! Some of us have been dealing with VVTi issues on 2GR-FE engines for going on 10 years now and have first hand knowledgeable about all of the possible causes of multi-cylinder misfires.

To the OP: You stored a hard code for 2 cylinders (codes 303 and 305), but you also logged the generic 300. Chances are if you were able to see the raw data, you'd find that at least one more cylinder (likely #1, the 3rd on that bank) is also occasionally misfiring but is below the threshold for logging a hard code. Per my printout you can see that they don't all misfire to the exact same extent. Some are just able to handle it better than others.

These diagnostic systems are sophisticated.
Actually they are not anywhere near as good as they should be. The basic methodology, hardware and sensor set dates back to the OBD-II inception (1996). Processing power and better algorithms improve the diagnostics, but it's still slow and imprecise. I attended a workshop on automotive failure mechanisms that included DRAFT OBD-III around 2008, and here we are 10 years later still dealing with a near 25 year old standard.

Yes advanced timing may cause a mis-fire, but if it won't generate a P0303 error code if there's a problem with the VVT unless the VVT is not sending a fault code (very unlikely, but possible).
I think we've already proven that this isn't necessarily true.

NET: There are a lot of possibilities and no reliable answers until the OP can retrieve all the data that is stored, or gets some proper live data (drive with a real-time datalogger) to show all that is happening. Anything less relegates you to an expensive parts swapping exercise.

You can certainly just go ahead and pull those two plugs and coils and it might solve the issue. But that's a good bit of effort and expense when you really don't know for sure what's going on. Sometimes it just pays to spend the hour's labor to get it diagnosed properly - especially on the rear bank.
 

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We've already proven this not to be necessarily true.

No you didn't. Your definition of PROOF is not something I'd except from any engineer that works for me.


Processing power and better algorithms improve the diagnostics, but it's still slow and imprecise.

Not a lot of processing power is needed. I've designed and written many many sophisticated diagnostic software systems for very sophisticated telecom systems. Automotive diagnostic is several hundred magnitudes less complicated. An auto MIGHT have a few dozen sensors. That's miniscule. Some systems I've worked on have tens of thousands of input points. Each auto sensor sends a reading to the ECU multiple times a second. This is stored in a table, and then the diagnostic software reads that information in real time and through simple algorithms determines if there's a problem and what the problem is. It's not that complicated system and doesn't need to be. A TI TMS32010 dsp chip from 1983 can easily handle the processing power required.


Heck, 24 hours ago you were talking about jumping timing chains!
If timing is advanced without the VVT throwing and error code then a jumped timing chain is a likely cause.
 

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I'm a development engineering team lead with 40 years in the biz. My lab is the 'Fire Dept', the one companies from all over the world turns to when designs aren't first time right. It's likely that your telecom system contains chips that my team helped push over the top.

Anyhow, I'm done here. I've shared my knowledge (some first hand experience, some insider information). Don't believe me? Great. Take over and lead the investigation.

To the OP. Get some professional advice before you tear into your problem. Real knowledge is power.
 
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