2011 Toyota Camry; Cylinder 3 misfire at 60+mph; P303 & P420

Morning everyone!

I’ve been dealing with a 2011 Toyota Camry with the 2.5L 4 cylinder. The car has an oil consumption problem - about 1 quart every 500-1000 miles. The car starts and idles perfectly fine. 
The car began misfiring severely at 60+ mph with flashing check engine and traction control lights. If you let off the gas, once the light stops flashing, it behaves normally until you get to that 60 MPH mark again. The DTCs returned were P303 and P420. Spark plugs are fairly new, I’ve swapped coil packs to rule them out and just finished replacing injectors. Problem remains on cylinder 3 with new injectors however, now it is misfiring around 75MPH. 

Compression test checked out good. All cylinders were at 210 PSI
Completed a leak down test on cylinder 3 and got virtually 0 leak at 100psi. Left cylinder pressurized for about 20 min with no change. 
No back pressure on catalytic converters. 
dropped exhaust to verify that cats weren’t clogged and noticed that they were actually gutted. Which would explain the P420 code. 
Stuck my borescope down into cylinder 3 and captured some images. 
performed smoke tests and have found 0 leaks. 
I believe this model has flaps on the intake manifold. Could the flap on cylinder 3 be faulty and cause this misfiring under higher load?

Is it valid to assume the oil consumption is occurring at higher engine loads and getting past the rings, specifically on that one cylinder? It’s there anything else I could possibly check to diagnose this misfire? Any PIDs I should monitor using my scanner or anything I should collect data on with a lab scope?


Thanks! 

That sure looks to be an awful lot of oil in that cylinder. I imagine the plug must be continuously getting oil fowled.
I have never seen an intake runner issue cause a single cylinder misfire at any load, I am willing to bet the oil consumption is the root of the misfire.

Tend to agree with Noah on the intake runner causing the miss. This particular intake runner setup has been pretty reliable over the years, in my experience. I can't really think of a way to pin that down short of intake removal.

Gonna disagree and say that, while the oil in the cylinder really is excessive, it's not causing the miss. I see these engines burning oil all the time - none of them miss at highway speeds because of it. Plus, your compression and leak down testing results are excellent.

How did the #3 plug look when compared to the others? I know you said the plug is new, but I'd be tempted to move it to another cylinder anyway.

It’s there anything else I could possible check to diagnose this misfire? Any PIDs I should monitor using my scanner or anything I should collect data on with a lab scope?

If possible, it may or may not be useful to monitor fuel trims during the misfire. As a very general rule, ignition misfires will cause a positive trim change of about 10% during the misfire. Lack of fuel will be about +20%. This method requires that you monitor the trim levels before and during the miss. It also requires that the fuel system stays in Closed Loop, otherwise the trims are invalid. Many vehicles force Open Loop during a flashing MIL, so keep an eye on the loop status.

Do you agree that a single cylinder miss is taking place? As in, do you feel engine roughness or lack of power?

Thank you Noah! Thought it was a pretty alarming quantity as well! I will upload an image of the plugs I replaced when I first encountered the misfire. Surprisingly as bad as the were, the misfire was still only on cylinder #3

Tyler wrote:

Tend to agree with Noah on the intake runner causing the miss. This particular intake runner setup has been pretty reliable over the years, in my experience. I can't really think of a way to pin that down short of intake removal.

Gonna disagree and say that, while the oil in the cylinder really is excessive, it's not causing the miss. I see these engines burning oil all the time - none of them miss at highway speeds because of it. Plus, your compression and leak down testing results are excellent.

How did the #3 plug look when compared to the others? I know you said the plug is new, but I'd be tempted to move it to another cylinder anyway.

It’s there anything else I could possible check to diagnose this misfire? Any PIDs I should monitor using my scanner or anything I should collect data on with a lab scope?

If possible, it may or may not be useful to monitor fuel trims during the misfire. As a very general rule, ignition misfires will cause a positive trim change of about 10% during the misfire. Lack of fuel will be about +20%. This method requires that you monitor the trim levels before and during the miss. It also requires that the fuel system stays in Closed Loop, otherwise the trims are invalid. Many vehicles force Open Loop during a flashing MIL, so keep an eye on the loop status.

Do you agree that a single cylinder miss is taking place? As in, do you feel engine roughness or lack of power?


 

Thanks for the response!

Trying to avoid removing the intake if possible. Also assumed there would be other codes/behaviors if this was the root of the problem. 

Compression and leak down tests surprised me considering the amount of oil I saw in there. Can we really rule out the excessive oil in the cylinder even though our tests aren't carried out under typical operating conditions when traveling at that 75 MPH mark? 

The new spark plug did not look any different than the others; I will try to snap a picture tonight. I'll upload a picture of what the old plugs looked like when they were replaced about a month ago.

I will admit fuel trims and O2 readings are my weakness. However, I'll dive into those tonight as well and try to provide some data. When the misfire begins, there is a shaking/vibration felt immediately while the CEL flashes. I can't say I disagree or agree with a single cylinder miss, how would that differ from multiple cylinders missing? I have mainly been keeping my eye on the misfire counter PIDs. The only one that reports the miss is #3 so that's where I've been focusing my attention!
 

Plugs that were replaced!

Can we really rule out the excessive oil in the cylinder even though our tests aren't carried out under typical operating conditions when traveling at that 75 MPH mark?

Nope! Can't rule it out. Just haven't run into a Toyota that breathes enough oil to directly cause a miss. Yet.

Plugs that were replaced!

Whoa! Those are crusty. Is the top plug missing the center electrode? 

 

I know you're concerned about the #3 cylinder, but it really looks like all four are consuming oil.

When the misfire begins, there is a shaking/vibration felt immediately while the CEL flashes. I can't say I disagree or agree with a single cylinder miss, how would that differ from multiple cylinders missing?

OK that's good enough. I mostly just wanted to make sure that the ECM wasn't flagging ghost misfires.

Tyler wrote:

Can we really rule out the excessive oil in the cylinder even though our tests aren't carried out under typical operating conditions when traveling at that 75 MPH mark?

Nope! Can't rule it out. Just haven't run into a Toyota that breathes enough oil to directly cause a miss. Yet.

Plugs that were replaced!

Whoa! Those are crusty. Is the top plug missing the center electrode? 

 

I know you're concerned about the #3 cylinder, but it really looks like all four are consuming oil.

When the misfire begins, there is a shaking/vibration felt immediately while the CEL flashes. I can't say I disagree or agree with a single cylinder miss, how would that differ from multiple cylinders missing?

OK that's good enough. I mostly just wanted to make sure that the ECM wasn't flagging ghost misfires.

yeah they were all pretty crusty I was surprised it was able to run as good as it did with those in there. Electrode may or may not have been missing. They were so bad I didn’t even mess with them. 

There is definitely oil consumption in all cylinders. I’m just trying to figure out if 3 is the worst of the bunch and thus causing the miss. 

Sorry for answering everything all together. Fairly new to the forum, still haven’t figured out how to respond to individual sections of posts lol here is the current state of plug #3 (inside spark plug socket) and plug #2 (held by hand)

Waiting for some hardware to come in for the exhaust flange so wasn’t able to watch fuel trims, will try to get data tomorrow night!