PO278 and PO306 codes and smoking

20156point7

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coming home earlier today I noticed the truck started to miss a little and started blowing a little white smoke. Limped home and checked the codes and I am getting a PO276 and a PO306 CEL. Both of those have to do with cylinder number 6 misfire and cylinder contribution balance. Noticed the truck has been blowing white smoke occasionally and now while parked and idling it is bellowing out white smoke and running rough. I’m down for the count at the moment. What are the chances that injector 6 for cylinder 6 is bad? Or is it something else possibly? Anyone else had this issue?
 

DEEZUZ

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Any recent work to that injector/cylinder?

Take your oil fill cap off, is crankcase pressure high/puffing?
 

20156point7

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No work has ever been done with that cylinder or injector and the crankcase pressure is low and not puffing. This has me concerned for sure. I would like to get lucky and it just be the injector but it doesnt seem like a common issue with the 6.7s
 

DEEZUZ

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No work has ever been done with that cylinder or injector and the crankcase pressure is low and not puffing. This has me concerned for sure. I would like to get lucky and it just be the injector but it doesnt seem like a common issue with the 6.7s
It is not common.

I do compression tests before I just swap a new injector in. I've found more with cylinder issues then bad injectors
 

DEEZUZ

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But if your blowby is OK, then perhaps the cylinder is OK.
 

DEEZUZ

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Do you have a fuel shop near you that can test common rail injectors? Where ya at
 

20156point7

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A little update. I popped a new injector in on cylinder 6 fired it up and still doing the same thing. Strange thing is it’s not showing the codes it was before. No cel on the dash and missing and smoking bad.
 

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A little update. I popped a new injector in on cylinder 6 fired it up and still doing the same thing. Strange thing is it’s not showing the codes it was before. No cel on the dash and missing and smoking bad.

Did you program the injector? Also try clearing the high pressure tables and driving it, see if it gets better


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20156point7

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Did you program the injector? Also try clearing the high pressure tables and driving it, see if it gets better


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I did not program the injector. I am still throwing the same codes as before. I feel like even if the injector needed reprogrammed it wouldn’t be showing the same exact symptoms and codes as the bad injector would it?
 

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I did not program the injector. I am still throwing the same codes as before. I feel like even if the injector needed reprogrammed it wouldn’t be showing the same exact symptoms and codes as the bad injector would it?

Sometimes they do funny stuff if they’re not programmed. It tells the computer fuel flow from that hole so it can change pulse width to even out running


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20156point7

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You were right sir. Should have done a compression test to start with. My shop ran a relative compression test and cylinder 6 is showing low. Shop is saying it’s making a noise in the top end and could be a bad rocker arm. I am up to the task of pulling the valve cover off myself. This doesn’t seem like a very common issue with the 6.7s so I’m not sure if they are right or not.
 

DEEZUZ

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I don't like relative compression tests I've found them useful to find a completely dead cylinder and that's about it.

Buuuut..

I'd be cutting the oil filter open first before pulling VC and checking for metal
 

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