Cannot fix Single cylinder misfire under load.

What you should do is unplug the 2 fuel injectors for cyl #3 and go for a test drive and see what the fuel trims are while going up a hill, and compare that to what they are when everything is plugged in (if the same, it would suggest a no-fuel misfire, and like I said before, I think the direct injector is what would be used under load like this). Next, you can disconnect the connector for #3 ignition coil, and see what the fuel trims are. This should give you direction.

You'll probably need to hook up a scope to your ignition and fuel injector controls and use long wires so you can see it while replicating the fault condition. See if either are cutting out.

If you don't have a high end scan tool you should be able to take it to a shop that does and have them do it for you. And it won't cost a ton of money either. Checking play would involve removing valve cover and inspecting the reluctor (the thing that passes by the cam sensor) for damage to the notchs. (Ie bent away from sensor)as well as metal debris on sensor If none found then check if reluctor is loose but gently pushing and pulling on reluctor to see if it moves a bit. If sensor is mounted on front of timing cover versus top of valve cover check end play of the camshaft by pushing camshaft to back of cylinder head and the pulling it to front of cylinder head measuring the difference. This would be camshaft walk however this would effect multiple cylinders if this was the case. The only other possible thing I can think of besides injectors is rocker arms failing

JoshuaK wrote:

It's looking like you have a no-spark misfire, because if it were no-fuel, the fuel trims on Bank 1 would likely be more positive than they are.

What are your fuel trims during a heavy misfire?

I appreciate you pointing that out. Like I mentioned, I’m not familiar with what to look for with this type of system. Is there any way to see secondary ignition with backprobes, or do I need to get an amp clamp? I’m using a picoscope 2204a.

JoshuaK wrote:

What you should do is unplug the 2 fuel injectors for cyl #3 and go for a test drive and see what the fuel trims are while going up a hill, and compare that to what they are when everything is plugged in (if the same, it would suggest a no-fuel misfire, and like I said before, I think the direct injector is what would be used under load like this). Next, you can disconnect the connector for #3 ignition coil, and see what the fuel trims are. This should give you direction.

You'll probably need to hook up a scope to your ignition and fuel injector controls and use long wires so you can see it while replicating the fault condition. See if either are cutting out.

I’m not sure I can do that without de-pinning the connectors. Direct injectors are under the intake and each bank has one plug into the main harness. Port are easier to get to but still just the single plug per bank for the injectors. Coil pack is fairly easy to get to.
How would I go about testing with a scope?

You may have to de-pin wires at the PCM/ECM or any connector along the way that you can access.

As for spark: Since you've swapped/replaced coils and spark plugs, you shouldn't be concerned with secondary ignition, but rather ignition control coming from the ECM/PCM. You can test both control as well as current to see if the primary side is working. Current is tested via a current clamp, and often the best way is to install a fuse buddy at the fuse that powers the ignition coils (and you can do the same for fuel injectors), and use your current clamp on that wire that goes between the 2 terminals on the fuse.

JoshuaK wrote:

You may have to de-pin wires at the PCM/ECM or any connector along the way that you can access.

As for spark: Since you've swapped/replaced coils and spark plugs, you shouldn't be concerned with secondary ignition, but rather ignition control coming from the ECM/PCM. You can test both control as well as current to see if the primary side is working. Current is tested via a current clamp, and often the best way is to install a fuse buddy at the fuse that powers the ignition coils (and you can do the same for fuel injectors), and use your current clamp on that wire that goes between the 2 terminals on the fuse.

Ok, I’ll have to order an amp clamp.

Can I also measure resistance in the trigger wires from the ecm to the coil? It’s an intermittent problem, so if the wires are the issue, im guessing I’d see a slightly higher resistance than the other trigger wires?

Do you have a 3- or 4-wire coil? If so, the trigger wire is very low current -- it's just a 4-5v signal firing a transistor in the coil, so resistance isn't going cause this kind of a fault.

FYI: My Hantek current clamp is a copy of the Pico and it works well, for $60-80.

JoshuaK wrote:

Do you have a 3- or 4-wire coil? If so, the trigger wire is very low current -- it's just a 4-5v signal firing a transistor in the coil, so resistance isn't going cause this kind of a fault.

FYI: My Hantek current clamp is a copy of the Pico and it works well, for $60-80.

I’m making assumptions honestly. If I have an intermittent issue with a misfire with only one cylinder and I’ve tested the coils, plugs, ecm, valves and compression, then I’m looking at a wiring issue right?
That why I asked about testing resistance. I figured I’d see a difference between that cylinders trigger wire vs the others.
To be realistic, I’m not sure what to actually test. I don’t mind ordering another tool if need be, I just haven’t had a chance. My wife’s parents died last year and we just got back from their estate where we had to clean it up and have a sale. Luckily that went well and we’re now back at home where I can concentrate on fixing this thing. But again, I just don’t know where to look. I’ll order the hantek clamp today, I just want to make sure the connection is correct.
Btw, it’s a 4 wire cop

I think looking at the ignition and injector current patterns during your fault condition is the next step. If those both look good, then it must be a compression problem. Have you swapped or replaced the #3 direct injector? Another thought is you could unplug all the direct injectors - perhaps the car will run on the port injectors as a back-up, and if you don't have a problem, then that tells you it's injector #3 or the control to it (unlikely).

JoshuaK wrote:

I think looking at the ignition and injector current patterns during your fault condition is the next step. If those both look good, then it must be a compression problem. Have you swapped or replaced the #3 direct injector? Another thought is you could unplug all the direct injectors - perhaps the car will run on the port injectors as a back-up, and if you don't have a problem, then that tells you it's injector #3 or the control to it (unlikely).

Ok. I got the amp clamp today. I gotta make a loop for it since i didn’t want to spend $20 on a piece of wire and then I should be able to test the current on the injector circuits as well as the coils. I am assuming I’m looking for cylinder 3 to mot match the other 5?

As far as compression is concerned, I did a compression test and got 150 psi. To confirm good compression, I also did a leak down on all three of bank one cylinders and they were all the same with a leak percentage of about 3-4 percent.

Correct, during your fault condition, you're looking for the current ramp pattern to to match the other 5 injectors.

Testing compression isn't useful because this problem only happens under load / i.e. high cylinder pressure. My guess is the problem is not compression. If you can't find the problem with spark or fuel, perhaps then you'll be replacing rocker arms, valves, and valve springs.

JoshuaK wrote:

Correct, during your fault condition, you're looking for the current ramp pattern to to match the other 5 injectors.

Testing compression isn't useful because this problem only happens under load / i.e. high cylinder pressure. My guess is the problem is not compression. If you can't find the problem with spark or fuel, perhaps then you'll be replacing rocker arms, valves, and valve springs.

 

   I was able to mess with it a little yesterday, but not enough for all the tests needed mostly because I got unexpected results from the first one. I still need to take it on an actual ride with the scope hooked up. I hooked up the current clamp to the power feed for all coil and then triggered off of cylinder 3 injector. What I see is consistent looking waveforms on all cylinders except cylinder 1 which has the same curves, but is a lower amperage. Cylinders 2-6 all show an average of 11.3 amps but cylinder 1 is at 9.1 amps. 
This threw me off because I was expecting to see an issue on 3, so I kept retracing wiring to make sure my trigger was on the right injector. 
I will to to do the other idling tests today to make sure I have it all hooked up correctly and then I will drive it and get it to do it’s thing. 

Your sample rate seems to hover around 6ks/sec which would be very low......

You may have to account for that the injection event does not take place anywhere near TDC compression, especially on port injection but often time also on GDI, depending on the operation mode. So make sure your sync event really happens when it it should in order to get the cylinders identified corecctly.

Eventually you may want to sync on a specific coil using the trigger signal or a secondary wand/probe, just to avoid possible confusion.

Ok, I’ll try again with a coil trigger and see if that will pinpoint it.

I did this same test again and you are correct. I triggered off of number 3 coil and it lines up with the one with one that is lower in amperage than the rest. Now my question is, why?

  I was able to drive the truck with the scope hooked up last night and made the misfire happen. On the picoscope, I'm seeing that the red channel, which is spark, simply turns off and stays off until I'm able to get to side of the road and turn the engine off and restart it. I don't see anything leading up to that though. The amperage draw is still lower than all the others, but it doesn't change throughout the event. 

 

After restarting, I drove home just a few miles away. When I pulled into the drive, I could feel the miss at idle. I watched the scope and could see there was no spark on 3. I blipped the throttle and the spark came back. Why would it do this?

I haven't done the tests on the injectors, but will try to do that today. 

Shouldn't be too tough to figure it out:

Or there is a problem = voltage drop or on the positive or ground side leg of these specific #1 coil circuits or it's the coil itself that got higher primary resistance than the other coils thus limiting current flow. Voltage drop testing will be your friend....

I didn't follow this thread from the beginning so I have a couple of questions:

Is the #1 coil same brand as the others?

When swapping coils will this #1 coil while put in another cylinder draw less current as well?

Will another coil put into #1 cylinder now draw less current than it did in the cylinder where it came from?

Just saw the images....If the red channel was spark why wouldn't it line up with the current ramp?

The coil may be shut down intentionally, you may want to check/verify that the injector is also shut down at the same time.

To get caught up quickly, you should read the first post. I have been at this for a while now. I am just now getting to the point of using a scope though.

The coil in question is a denso coil. I have replaced the coil on 5 and that is the only one that is aftermarket. I have swapped coils and plugs previously and the problam has always stayed on 3.