major misfire no 7 help please

[snowhemi]

So here is what is going on.
Have a 2009 1500 with 5.7 hemi.
Truck is misfiring so badly it shakes the truck while doing it. Only code is a p0307 every time.
If rpms are high like 5k its not notable. Til drops down and MDS kicks in at 1400 doing 60.

I changed plugs. Swapped coils swapped the injector. I have ran 89 octane minimum.
I have put a bottle of seafoam in throttle body over a few hour time before new plugs.
I have .25 of a quart of marvel mystery oil in oil. I have ran 2 quarts in gas. I pulled the valve covers no visible damage to springs but new plugs in number 7 are black. Cylinder is clean with my camera scope. Did a compression test on 7 and its at 215psi and holds it there.
Also sprayed carb cleaner and brake kleen around intake and head gaskets with no idle change.

Tester broke before could compare with another cylinder. All this and can't figure it out. Willing to try any and all suggestions. Thanks in advance.

 

[japowell03]

Only thing left I can think of is checking for power at the injector. Should be always hot, I'm pretty sure the ecu switches the ground side off and on to actuate it. How did those injector seals look? Checked vacuum lines already? I would pull the valve cover and watch as someone turns the crank a few times. Most of this doesn't make sense either because you have a black plug and good compression...

 

[B-g-K]

No metal in the oil right?

 

[snowhemi]

Set ohms to 200 or another setting? Seals looked great. Put a little oil on when put back together. Truck has 72800 I bought with 61500.

 

[TylerB]

Have tried moving the coil pack to a different cylinder to see if follows that coil?

 

[NYCruiser]

Sounds stupid, but have you changed the plug wires to #7? You didn't mention it.

Figures it would be the one under the brake booster.

 

[snowhemi]

Correct. No metal. I put in synthetic cause did not know what it had in there. And was 4 miles from my work shop to change oil when this started.

 

[snowhemi]

Yes I moved the coil. Tested the coil and it is .6 so in spec. No vaccum leaks.

 

[japowell03]

Set it for vdc should have power at the injector plug with they key on. I'm not positive it will on these trucks though, so verify whatever you find with another one. Use a chassis ground not the negative in the plug.

 

[PaxtonScarborough]

Either there's no voltage to the coil or injector, or the PCM isn't controlling one of them properly, also could be a wire chewed or frayed.

 

[B-g-K]

I'm sure you've checked all your grounds already right?

 

[snowhemi]

Set it for vdc should have power at the injector plug with they key on. I'm not positive it will on these trucks though, so verify whatever you find with another one. Use a chassis ground not the negative in the plug.

I'll do that tomorrow. Thanks y'all.

What is the proper way to test power to the coil? I tried once with no luck. My issue comes and goes :/ if it is mechanical I'd have warranty they want 100 per hour to do what I have been doing if they find no issues. Like me.

 

[japowell03]

Either there's no voltage to the coil or injector, or the PCM isn't controlling one of them properly, also could be a wire chewed or frayed.

Yeh could put a plug in the coil removed but plugged in, and try to spark it against something metal and unpainted. Have someone start the truck, wear a glove (dry) or it will zap you pretty good. If that works and you have voltage at the injector safe bet it's the PCM.

 

[snowhemi]

I'm sure you've checked all your grounds already right?[/QUOTE

Ya I have. At least I believe all grounds.]

One ground strap nobody talks about anyplace I seen underneath the tranny on the cross member for the tail shaft there is a strap and I have no clue where that clip clips on at. I see no worn spots. I know not related to my issue but ideas?

 

[snowhemi]

Yeh could put a plug in the coil removed but plugged in, and try to spark it against something metal and unpainted. Have someone start the truck, wear a glove (dry) or it will zap you pretty good. If that works and you have voltage at the injector safe bet it's the PCM.

Easy enough. Just like if it had wires.

 

[snowhemi]

Easy enough. Just like if it had wires.

No luck. I pulled the coil. Ground the plug and I have great spark.

 

[japowell03]

Pull that valve cover and take a look. Springs could be good but still could be a bent pushrod bent valve or collapsed lifter. See if the rods have any play.turn it over by hand and watch the rocker arms going up and down. Not much left to look at. Pull the radiator cap and start the motor.see if it it's blowing bubbles...

 

[snowhemi]

I'll pull the cover again. Getting good at it. Haha
Bubbles indicate what exactly? Cracked head? Tore gasket?

 

[snowhemi]

It comes and goes sometimes. If in neutral it will not misfire. If I power brake it it will at 1500 if held for 45 seconds.

 

[japowell03]

It will show you a failed head gasket sometimes.they fail in different ways a shop can do a full leak down test on that cylinder and give you a lot of good info a regular compression check wont.