Misfire can’t find the issue.

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dshaff45

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Well we rebuild the top end, new cam, new lifters complete DoD delete all new gaskets all the way around got everything put back together. Everything was perfect no misfires no rough idle. After a week of driving P0335 Crankshaft position (CKP) sensor circuit code came back, tach stopped working again but no misfires. Was really hoping to get it code and light free to send it down the road to a new owner but now seems back to square one. Replaced the crank sensor again, new wiring to the crank sensor as well, all grounds replaced that I have found, with no fix.
 

Geotrash

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Well we rebuild the top end, new cam, new lifters complete DoD delete all new gaskets all the way around got everything put back together. Everything was perfect no misfires no rough idle. After a week of driving P0335 Crankshaft position (CKP) sensor circuit code came back, tach stopped working again but no misfires. Was really hoping to get it code and light free to send it down the road to a new owner but now seems back to square one. Replaced the crank sensor again, new wiring to the crank sensor as well, all grounds replaced that I have found, with no fix.
That seriously sucks. Sorry to hear it. FWIW, I still think your problem is electrical. Either the sensor isn’t sitting perfectly where it’s mounted, or you have a problem in the ckp sensor circuit.
 

ls1frc

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I just fixed weird electrical issues in mine and was causing the crank pos sensor code but was not related to that at all. I replaced both battery terminals (1 black wire, 2 red wires to starter and alternator).

 

boblee53

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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.
I had some of these same issues. All kinds of dash warnings , a low rpm miss, Power steering jerk , it would die & hard to start. I check the 6 mo old battery & it was crap. I replaced the battery & cleaned the grounds. It ran great for a week. Died again on a interstate on ramp. Started right back up, but dash lights flashed & headlights would not shut off. I had the battery cables replaced after reading a post on here & replying back & forth. As he said. Not a problem since. I own a 2016 Yukon XL SLT 5.3 GM had cable problems for a few years after 2014 ,but good luck getting them to admit it.
 

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