P0316, P0306, P2272

[Montanomo Bay]

Hello, I have a 2006 3.0 that has a nagging misfire and o2 sensor problem. I have done all of the following:
New plugs
New wires
New coil pack
New O2 sensor
New fuel filter
New injectors
Compression test: cyl 6 @ 105

The o2 sensor keeps causing a solid check engine light, even though it's new. I have a crack in my driver's side exhaust manifold, but not sure if this is causing the misfire as well. I'm going to swap it out after tomorrow. I will update on if this resolved P2272 issue.
Regarding the misfire, I just had the heads replaced about a year ago. I don't expect this to be the issue. Also, I've had some recent shenanigans with the crash detector switch cutting off fuel to the engine for no apparent reason. I just need to reset the switch when it happens, then I'm good to go. Otherwise, I have a random flashing cel, things get shakey, I lose power, then give it some gas and it comes back to normal.
After replacing all of the parts listed above, the truck runs GREAT!!! I just cannot shake these codes.

Please let me know if I can provide any additional information. Thanks!

 

[adsm08]

You need to fix the misfire issue before doing anything else.

The 2272 code is for a post-cat sensor not switching the way it should. When a misfire happens it dumps raw fuel into the exhaust. If you have a working cat the fuel burns off in the cat and will spike the downstream O2 sensor voltage, and keeps it high.


What are the compression numbers for your other five cylinders?

 

[RonD]

Because its a 2006 you will need to do full compression test
All spark plugs removed
Throttle wide open
Test one cylinder at a time and write down results

Do WET test on low cylinders to determine if its rings or valves that are leaking

2004-2006 Ranger 3.0l TSB here: https://therangerstation.com/ford_ranger_buyers_guide/Ford_technical_service_ bulletin_tsb_05-26-3.shtml

 

[Montanomo Bay]

1 = 140
2 = 140
3 = 140
5 = 130
6 = 120 first time, then 105
Didn't test 5.
I may need to retest compression tho. I wasn't aware the engine needed to be warm

 

[Montanomo Bay]

I'll do that, and come back with better results. I guess I was hoping for a quick fix

 

[Montanomo Bay]

My compression test numbers were taken while the intake plenum was off... Not sure if that matters or not. Engine was cold too

 

[Montanomo Bay]

One more thing, Haynes book says that as long as the compression is at 100 minimum I should be good. This really threw me off...

 

[RonD]

Engine doesn't need to be warm, not sure why that is still going around, lol, yes after doing a cold test you can then do a warm test, but always cold test first, then decide if warm test might give you more info

Gasoline needs 100psi static compression to be heated up enough to be vaporized so a spark can ignite it, thats what they are referring to

A vehicle engine usually runs 9.0:1 compression ratio so minimum is about 150psi

Your 2006 3.0l runs 9.3:1 so would expect 165psi or so

But............this really depends on the test gauge, usually they are not calibrated between tests, lol

So full compression test is done to compare all cylinders NOT for the exact numbers

Your cylinders 5 and 6 should be tested again and then tested after adding a teaspoon of oil
Just use a straw and dip it half way in a bottle of oil then lift it out and put it in spark plug hole and take finger off the straw
Then retest
The oil will seal the rings better, so compression WILL go up, but if it doesn't go up to 140 then Valves are leaking not the rings

And it could be a blown head gasket between 5 and 6, so.............
But either way it looks like your heads will need to come off

Not going to fix it from the outside

 

[adsm08]

One more thing, Haynes book says that as long as the compression is at 100 minimum I should be good. This really threw me off...

Haynes book is.... sketchy.

90 PSI is the minimum for the engine to run, but a misfire in and of itself does not make the engine buck. What you are actually feeling is the sudden imbalance in the engine's rotation. When compression lowers power contribution lowers. In a cylinder is down more than 10% from the others it will drop the contribution enough to be felt.

 

[Montanomo Bay]

Nice hack, I'll try it out and update the forum

 

[Montanomo Bay]

Thanks adsm08. Can the crack in the exhaust manifold cause misfire codes?

 

[Montanomo Bay]

@RonD , are those both issues that I could DIY fix or would I have to send to a shop?

 

[RonD]

You would either get new heads or send yours to a machine shop to be serviced
But you can DIY the removal and re-installation of the heads, its just wrench work

You need new head bolts and a head gasket kit(this has intake, exhaust and valve cover gaskets as well as head gaskets)

 

[adsm08]

Thanks adsm08. Can the crack in the exhaust manifold cause misfire codes?

No. Misfire is based on the measured acceleration of the crankshaft. An exhaust leak will not have any bearing on that.

The only way a cracked exhaust manifold will cause a misfire code is if it burns the valve.

@RonD , are those both issues that I could DIY fix or would I have to send to a shop?

A competent DIYer can replace a cylinder head. If rings are your issue, you might as well find an engine.

 

[Montanomo Bay]

Doing dry compression test now and will update results for each cylinder shortly...
On a separate note, here is a shot of all 6 plugs I just pulled out: