Misfire can’t find the issue.

[exp500]

I'm not sure about the circuit, if there is a tach ground in the dash it is a possible failed tach.

 

[Doubeleive]

@swathdiver @iamdub
any ideas?
op I would check over the ecm harness
I wonder if a poor ecm connection would throw a misfire code/loss of tach?

 

[Fless]

Loss of tach would be a symptom of a bad crank sensor or circuit issue. Also, has a CASE relearn been attempted?

https://www.cardone.com/content/Products/PT70-77-0003.pdf

 

[dshaff45]

So after today, swapped in ANOTHER crank sensor did not fix the issue even after the re-learn but then proceeded to hear more of a tap at the WOT portion of the relearn. Pulled the valve cover off still nothing specifically on bank 2 cylinder 4. Found a loose bearing on a rocker arm, not convinced this has anything to do with misfire, but more so for noise. Not good nonetheless though. Will be digging in more tomorrow.

 

[Fless]

Compare the cluster tach rpms with a scanner reading live data to see if they are doing the same thing at the same time.

 

[Foggy]

So after today, swapped in ANOTHER crank sensor did not fix the issue even after the re-learn but then proceeded to hear more of a tap at the WOT portion of the relearn. Pulled the valve cover off still nothing specifically on bank 2 cylinder 4. Found a loose bearing on a rocker arm, not convinced this has anything to do with misfire, but more so for noise. Not good nonetheless though. Will be digging in more tomorrow.

Describe better what you mean as a "loose bearing on a rocker arm"
They either have all their roller bearings or they puke them into the engine when they fail...
Or is the rocker just very very loose compared to others - which would suggest
a wiped cam or lifter issue

 

[mikez71]

The wiring and sensor maybe OK, but that doesn't mean you are getting a good signal?
Maybe something with reluctor wheel?

found this online..

"One of the most common symptoms of a bad reluctor ring is going to be a rattling sound. If the engine still runs, you will hear it. This means that it has been damaged, and no longer seated properly."

Best to try and log the signal, unfortunately I'm not able to tell you what the signal should look like!

 

[dshaff45]

Rocker armThe loose rocker arm has lots of lateral play in the bearing. The attached link is very similar to mine.

 

[swathdiver]

It is my belief that some of your problems are not related.

Do you still have access to the Tech-2? For code P0335 did she exhibit Condition 1, 2 or 3? Was the airflow into the engine at idle greater than 3 g/s?

Also, you must use GM OE or ACDelco components. Aftermarket sensors almost never work. In the least, they are not calibrated to play nice with the computer system.

 

[Grizzlygibbs]

I have a 2012 GMC Yukon SLE with 5.3L. My problems started with a P0300, and since the vehicle has high miles, I ordered new coils, plugs, and wires. My #4 spark plug was wet, and the rest looked fine. I changed the plugs and wires at this time. Two days later, I got an MAF code, which I proceeded to replace the MAF, and the code cleared immediately. About a week went by, and as I was leaving for work, the car died while driving. I was unable to get the vehicle started. After verifying I had fuel pressure and spark, so I assumed it was the cam or crank position sensor. I replaced those, and after a long crank, I got it started. I got access to a Tech 2 scan tool and did a crank relearn procedure. The next day, the car seemed to be running fine, and then I got a low oil pressure message. The gauge would start normal and slowly drop to zero. I replaced the screen and sensor and haven't had an issue since (I believe this may be unrelated to other problems). Next, I took the Yukon for a test drive to monitor oil pressure, and once I was warmed up. I gave the vehicle heavy acceleration. Then, I got a flashing check engine light, traction control, and a noticeable misfire. I got my car home, and I was worried I hurt the engine during acceleration I proceeded to do a dry compression test, which was 160 psi, close to all the others. I also did a cylinder leak-down test, and it was around 3% leak-down. My coils arrived, so I replaced those with no improvement. I was getting P0304 and another code for the rich fuel mixture Bank 2. I checked the #4 cylinder with a timing light, and it seemed like I had a consistent spark, so I decided maybe the fuel injector was the culprit. I replaced that with no improvement, as well. The next time I went to start the vehicle, it was a long crank followed by P0335 (Crankshaft Position Sensor "A" circuit), so I felt like I finally had something to go off of. I looked up the troubleshooting instructions for the crank circuit, and everything tested fine. Checking ground and the 5v signals, I moved around the harness to try and find a possible open or short, but the signal never fluctuated. This has been very frustrating, and I'm running out of ideas. So, right now, I am showing a consistent #4 cylinder misfire, CKP circuit code, and long cranks. Also, I removed the valve cover to inspect the upper valve train and watch for proper rocker operation on Bank 2. And I’ve also replaced the ECU with same issues following. Any help would be greatly appreciated, I’m at a dead end right now.

This exactly happened to me last week. With most all of the same code. I did a transmission control reset, cleared codes, and made sure oil was topped off. It was wet/snowy when this happened to me, were you in 4hi by chance? Anyway, mine has yet to come back after all that but it has also not been as wet out.