Working on a factory 2004 Isuzu asender with the 5.3, motor has a miss so I checked and cleaned all injectors, changed the coil packs and now still have a miss in the number 2 cylinder. Later proceed to change PCM and and chased wire, still have a miss. Checked spark with new spark plug and it's a no. What in the world am I missing? Could it possibly be the crank sensor? If that were true wouldn't it be erratic?
Signed
Defeated
Check compression?
2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.
If you don't post your tune and logs when you have questions you aren't helping yourself.
Not yet, just curious how does compression tie in?
Low compression will give you a misfire.
You've already done the spark plug, the wire, swapped injectors and coil packs around so now it's time to internal stuff.
So compression test, leak down test. Check for a broken valve springs. I would rule all those things out before jumping to other sensors.
2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.
If you don't post your tune and logs when you have questions you aren't helping yourself.
Copy that , thank you
125 psi compression with a small bit of fuel on it
Seems low. If I recall most seems to be around 160-180 and the minimum compression is around 100-110.
2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.
If you don't post your tune and logs when you have questions you aren't helping yourself.
Researching showed that's about normal for the mileage, concerns are I hear a "ticking" on that cylinder, going to remove the head and see what's up
Leak down test is always a good idea. I had an engine that compression test said was okay but leak done showed the issue.
I missed one part of your first post. Does it still not have spark on cylinder 2 or was that fixed when you were checking the wiring/injectors?
2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.
If you don't post your tune and logs when you have questions you aren't helping yourself.
Running compression or leak down. Another quick thing on a 5.3 is to pull the valve cover and fire it up and let it idle. This will show spring and lifter issues. Depending on 5.3 you may even have all of the rings stuck in the ring lands killing compression.
2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80
~Greg Huggins~
Remote Tuning Available at gh[email protected]
Mobile Tuning Available for North Georgia and WNC
Still no spark, still no injector fire on num 2 cylinder
Kill the codes and see if injector and spark come back - most likely the ECM is killing these due to the misfire and not them causing the misfire...
2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80
~Greg Huggins~
Remote Tuning Available at gh[email protected]
Mobile Tuning Available for North Georgia and WNC
Leak down is good, pulled valve cover and everything is operating normal, cleared codes and it ran ok for a minute and back to crappy. 182 misfires I'm 2 minutes, Huston we have a problem, tomorrow I will change crank sensor and O2s as I am grasping at straws.
Did you perform the leakdown correctly - very easy to not do right - you have to set main gauge to 100psi before you ever hook it up to the cylinder hose - what was the leakage percent?
Compression is low - should have been a lot higher... Crank sensor and O2's won't fix that... O2 is possible, but usually you'll see misfires on the other cylinders on that bank as well with cylinder 2 or rather your front cylinder being the primary misfiring cylinder - cat will cause the same thing... What is running compression compared to another non misfiring cylinder? Was the spark plug oil coated?
2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80
~Greg Huggins~
Remote Tuning Available at gh[email protected]
Mobile Tuning Available for North Georgia and WNC
A friend of mine that owns a machine shop came by and lent me his leak down tester and also assisted in the test so I'm feeling confident it's not a mechanical issue, I tested 2 other cylinders with a +- 10psi differential. It should not be a crank sensor otherwise it would be erratic but again I'm grasping at straws at this point. Reminds me of the last LS motor I transplanted that would only foul out the two rear plugs on opposite sides until I uploaded a new tune, strange things happen to me.
Spark plug was fuel fouled, when the motor first starts or the codes are cleared it runs normal for about a minute then resumes misfire
Using factory heat range plugs? Leak downs if not done correctly won't show anything. I've even had to use lower pressures to find worn valve seats. Running compression compared to a known good cylinder while the engine is hot will show you the problem if it's mechanical.
2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80
~Greg Huggins~
Remote Tuning Available at gh[email protected]
Mobile Tuning Available for North Georgia and WNC
I've done every single thing I can think of and still no fire to num 2 cylinder, just for giggles I changed the crank sensor and O2s and still no fire/injector pulse on num 2......pull the motor or burn it to the ground?
It's going to be a hassle but you may have to try pulling back the wire harness for the coils and injectors to inspect the wiring or replace it.
2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.
If you don't post your tune and logs when you have questions you aren't helping yourself.
I replaced every wire from a donor harness for coil pack and injector, owmed them out just to make sure all is good
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