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Hello, my name is ***** ***** I am a professional here at Justanswer. Thank you for your question and I will assist you with your concern.Are you able to scan the system and if so are there any fault codes setting?
The backfiring as well as the stumbling still indicates you have a valve timing concern. Are you able to monitor the CKP signal while the problem is occurring?
Can you do that and see if the signal is consistent as well as looking at the HO2S sensors signal to make sure there switching normal?
The HO2S sensors working properly should not exceed 1.0 volts. The Powertrain Control Module (PCM) on this engine allows the O2 sensor signal to determine 33% of the fuel control. If the O2 sensor voltage remains too high as the PCM moves to closed loop, the controller will take away fuel. This can be seen on a scan tool, by watching the long term adaptive memory parameter.
The common cause is a failing HO2S sensor, if your sure the HO2S is okay then the other cause would be the PCM (computer).
Are you referring to HO2S 2 as the downstream sensor?
Okay if that is the case your readings look fine. I suspect your dealing with a bad PCM if you are not setting any fault codes but with out it setting any fault codes it would be hard to be 100% sure.
The code P0320 is in most cases caused by a failing CKP but since you have replaced it I would suspect you may have a circuit concern from the CKP to the PCM, that could also cause this type of backfire. How dose the CKP signal look when the problem is occurring?
Let run the test in the link below and see if the results check okay.https://dl.dropboxusercontent.com/u/104923897/CKP%20testing%20Sep%204.pdf
Which circuit are you needing?
Okay sure thing. See the complete engine control system in the links below.https://dl.dropboxusercontent.com/u/104923897/PCM%201Sep%204.pdfhttps://dl.dropboxusercontent.com/u/104923897/PCM%202%20Sep%204.pdfhttps://dl.dropboxusercontent.com/u/104923897/PCM%203%20Sep%204.pdf
If the wiring and the signal at the CKP check okay as stated I would suspect the ECM may be at fault.
Did you ever run the test steps I sent you .
This sure sounds like a wiring issue to me.
Im showing ground at pin A 31 and A 32 to ground at ground 117 at the right rear of the engine . The HO2S sensor also use this same ground
Those are the 3 grounds Im seeing, two for the PCM and on for the HO2S.
If they where sticking open you would notice an over fueling condition and lots of black smoke.
If it was out of time in most cases it would effect the compression. It would not hurt to at least check the compression to be sure its okay. Have you ever verified you have good fuel pressure as well?
Your fuel pressure looks good. There has to be something going on here with the computer control system. Finding it is going to be the challenge.
In most cases if the ignition switch or the neutral switch was failing the engine would not crank . I bad ignition switch could cause issues if in fact you loosing voltage to the ignition.
See what Jeep offers in the link below.https://dl.dropboxusercontent.com/u/104923897/Ignition%20Switch%20Oct%209.pdfhttps://dl.dropboxusercontent.com/u/104923897/Ignition%20switch%202%20Oct%209.pdf