Hello,

Nearly all miles have been highway miles. On 2 separate occasions, P0306 code appeared, and then cleared on its own. 3rd time it appeared, all plugs and #6 COP were replaced.  Code returned shortly afterwards.  Went back in and replaced #6 Injector. P0306 code ever present.  P0306 is only code that has ever been presented. Any suggestions would be appreciated. Thanks

Misfire #6 cylinder.    Does it feel like it's running on 5 cylinders?     

Bad wire/connector to #6 coil over, vacuum leak at intake manifold or #6 runner,  low compression at #6 cylinder.   A vacuum leak could set another code of running to rich. 

 

Next time instead of replacing parts switch the part, like the coil over (COP), with the cylinder next to it then see if the problem moves to it. 

No, it does NOT act like it’s only running on 5 cylinders. There is no rough Idle, hesitation.
Could be a connector/wire at COP. “Physically” it looked good but never know. 

Ill check vacuum and #6 compression. 

On my 1996 it was a intake manifold gasket was sucked out of place and created a lean issue on number 6 which change sparks plugs, even the fuel injector. But ultimately the intake gasket was the issue. After replacement I've not had any issues again.

Thanks for replies.

I am looking into the vacuum leak.   
An intake leak is very possible. I’m amazed at the amount of plastic on this engine. Almost scared to use a Torque wrench on it. Just another reason I stay away from new vehicles

Torque wrench is very much required. Like Dodge 5.9L V8 Magnum engines are very low torque numbers.

3 hours ago, Leaky88 said:

Almost scared to use a Torque wrench on it. 

A torque wrench is needed when working on aluminum alloy engines.  Over tightening will pull the threads out.

 

There are 2 ways to find a vacuum leak at the intake manifold/gasket.

1. With the engine running spray the intake manifold/gasket with carb cleaner.  When the carb cleaner is sprayed on to the damaged area it is sucked in and will cause the engine to stumble.
2. With the engine running using a 5/16-3/8 hose about 3' place one end of the hose in your ear and run the other end over the manifold.  You will her a sucking sound when the hose goes over a damaged area.   Using a hose like this can also be used to find a bad bearing in a water pump, alternator,  etc.

 

 

Thanks.
For certain the fasteners will be torqued in sequence and to specs.  
I’m just saying there’s a lot of plastic being used on it which makes one wonder if it take any torque without breaking.
But,  I’m told Dealerships make very little on the sale of the vehicle.  

The biggest revenue comes from the maintenance and servicing of it once they set the hook in the buyer. 

One would hope the factory took the material into consideration with the torque specs.

7 minutes ago, dripley said:

One would hope the factory took the material into consideration with the torque specs.

Oh trust me they did! When I ordered a manifold gasket the paperwork had all the specs in the box. At least for my 1996 Gasser it was in INCH pounds for the bottom of the manifold. 

That’s what I’m talking about.
And even with Inch Pounds, you wonder if you should continue to the “click” and/or what the lead time might be on getting a replacement part when it shatters. 

Hand tools only. No air and leave the Milwaukee Impact in the Tool Room. 

Don't worry too much the inch pound bar (1/4 inch) is so light of a torque you have to feel the click as you slowly tighten. Kind of like doing band adjustment on a 47RE transmission you more or less feel the light click at 72 inch pounds. The part will hold up to the torque just don't beyond the click and go slow. It not so much that the part will shatter or break it more about getting a even clamping force on both side. Hence the torque wrench will aid in over tighten and give a even clamping force when done right.