Hemi misfire

Jeff Owner/Technician Ontario Posted   Latest   Edited  
Updated
Driveability
2011 Ram 1500 SLT 5.7L (T EZH) 5-spd (545RFE)
P0300 — Random/Multiple Cylinder Misfire Detected
Poor Idle

Hey all I have this truck in the shop setting misfire codes . Scan data shows cylinders 5,6,7and 8 misfiring and they must be because this thing idles rough . Doing some testing we found no coil current and no injector current for the cylinders that are misfiring . If the codes are cleared the engine runs and idles smooth on all 8 cylinders , the longer it runs cylinder 5 will start to misfire , and eventually 6,7and 8 join in . When all cylinders are running each injector and each ignition coil ramp up and are using the same amount of amperage . When the misfire is present the power to still supplied to the injectors and coils , the ECM stops controlling them . Relative compression test was done and we found all even leaks , We are leaning towards a faulty PCM once’s PCM powers and grounds can be confirmed . Has anyone been down this road before ? is their other test we should run before pulling the trigger in the PCM . Thanks in advance 

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Randy Diagnostician
California
Randy Default
 

Can you see misfire counts on only 5 on scan data ? What are fuel trims at this point

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Jeff Owner/Technician
Ontario
Jeff Default
 

Can see counts on 5,6,7and 8 when they are not being controlled , I did not look at trim ? I would imagine very lean numbers because of the misfires .

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Randy Diagnostician
California
Randy Default
 

Pcm fail safe save cat from to much fuel

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Albin Diagnostician
Washington
Albin Default
 

What are the trims doing when the engine is running on all cylinders? The reason it is shutting off cylinders is the PCM is seeing something it thinks is a misfire. Reset the codes, do a KAM reset and start your testing process again and see what red flags it waves for you.

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Nick Diagnostician
Missouri
Nick Default
 

6th one over looks a little low to me. It could be pcm strategy to kill injectors during misfire events. If it's a dead misfire it can give false misfires on other cylinders. Can you do cranking vacuum pulse? Or pull the valve cover in bank one and make sure the intake valve is opening

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Randy Diagnostician
California
Randy Default
 

Or in cylinder pressure transducer

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Jeff Owner/Technician
Ontario
Jeff Default
 

I will do cranking vacuum pull in the morning . I was monitoring amperage thinking The PCM strategy didn’t like one of the coils or injectors but didn’t see any indication of that .

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Scott Owner/Technician
Ontario
Scott Default
 

Very much doubt it’s a pcm, if you clear and the rig idles fine the pcm is in protect mode How about exh restriction on that bank ? i doubt bad fuel would effect that one side but it may be worth a look .

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Jeff Owner/Technician
Ontario
Jeff Default
 

It’s both banks 5-7 and 6-8 . I can believe the protect mode but I don’t know what else the PCM would be seeing that would put it into that strategy . Thacts why I was monitoring the current each injector and coil was ramping .

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Nick Diagnostician
Missouri
Nick Default
 

What cylinder are you synced on? And a dead mis can cause ghost misfire counts the PCM us just trying to save the converter and killing fuel

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Joe Owner/Technician
California
Joe Default
 

I believe cylinder layout is 1357 and 2468 on the hemi isnt it?

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Jeff Owner/Technician
Ontario
Jeff Default
 

Yes it is

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Joe Owner/Technician
California
Joe Default
 

Sorry didn’t realize you already responded to the above

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Joe Owner/Technician
California
Joe Default
 

Ive had the worn cam lobes/bad lifters bite me on these things before. I would do an in cylinder waveform

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Nick Diagnostician
Missouri
Nick Default
 

If you're synced on #1 that makes 6th one over #5. To me it appears slightly lower and the next one looks slightly higher. Being a 2012 I'm really concerned about #5 intake valve not opening all the way due to a roller locking up and chewing up the cam.

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Ray Diagnostician
Ontario
Ray Default
 

This 2016 Charger 5.7 had a P0301 and the PCM would stop triggering the coil and the injector. CH A is COP 1, CH B starter amps, CH C is pressure transducer connected to the intake, on a large port near the throttle body.

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Caleb Technician
Indiana
Caleb Default
 

Yes please put a first look in the intake along with your RC and sync. Do a long crank so you can get some repetition.

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Jeff Owner/Technician
Ontario
Jeff Update
 

Well I would like to thank you all for your help on this vehicle , your guidance forcing me to over look the PCM as the cause was what I needed to get this solved . I have pick files to share however I do not have them tonight . As suggested a vacuum trace was captured while running and didn’t look good . Mark Lemay from Auto Aide Technical Services walked me threw what I was seeing , and what I…

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Randy Diagnostician
California
Randy Default
 

good diag

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Albin Diagnostician
Washington
Albin Default
 

Broken valve spring on a 5.7 Hemi? Tell me it isn't true :) Nice diag!!

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Joe Owner/Technician
California
Joe Default
 

Can’t wait to see the pics ya got on file

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Jeff Owner/Technician
Ontario
Jeff Update
 

Here are the pico files , running intake waveform using wps500 zoom 3 , cylinder 2 running compression , cylinder 5 running compression

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Jeff Owner/Technician
Ontario
Jeff Default
 

screen shots

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