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Gary
Gary, ASE Certified Technician
Category: Chevy
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Experience:  Senior Technician
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2009 Avalanche P0307 Code along with Service Stabilitrak

Customer Question

2009 Avalanche P0307 Code along with Service Stabilitrak Replaced Coil, Injector, Plugs and wires.. Any thoughts?
Submitted: 1 year ago.
Category: Chevy
Expert:  GM Tech (Cam) replied 1 year ago.

Hi there, I am Cam. Sorry to hear about this issue.

Does it misfire only a bit or all the time?

Customer: replied 1 year ago.
only at idle, ok at higher RPMs
Customer: replied 1 year ago.
I gather
Expert:  GM Tech (Cam) replied 1 year ago.

Ok, this could be a leaking cylinder. We next need to do a couple tests. First cylinder leakage test to see if the valves are leaking, compression test, injector flow test after that. Are you doing the work yourself or what are abilities?

Customer: replied 1 year ago.
Ive replaced the injector as well as done a compression test getting good compression
Customer: replied 1 year ago.
seems to be linked to stabilitrak somehow
Expert:  GM Tech (Cam) replied 1 year ago.

The stabilitrack is only a symptom of the misfire. Its first action is to cut engine power when your slipping. So it disables that system.

So we need the cylinder leakage test done with the proper leakage tester that shows % of leakage.

Customer: replied 1 year ago.
There are several reports of this issue on the internet.. Its the dreaded p0307 code.. Is there not any fixes that you have become aware of.. I don't believe I have a cylinder issue.. It seems that this is computer related, as I get spark and fuel.
Expert:  GM Tech (Cam) replied 1 year ago.

That’s what strange. I usually see spark plugs or lifters that cause this. And to answer what I Am sure you are thinking, if you had an exhaust lifter fail, compression would be perfect.

Customer: replied 1 year ago.
Bad gas?? I had just filled it up...
Customer: replied 1 year ago.
My fuel pressure is fluctuating a lot too.. As low as 44
Expert:  GM Tech (Cam) replied 1 year ago.

That is very low. Spec on this engine is 55 to 62 PSI. What does your fuel trim show with the scan tool?

Customer: replied 1 year ago.
That is where I'm measuring it.. Scan tool shows as low as 44 and typically shows 58.. The miss is still present even at 58
Customer: replied 1 year ago.
It seems that it only shoots to 58 when the code presents itself.. Typical idle is 43-44?
Expert:  GM Tech (Cam) replied 1 year ago.

Fuel trim is a % not psi.

Customer: replied 1 year ago.
I don't see that
Expert:  GM Tech (Cam) replied 1 year ago.

IT would be expressed as STFT or LTFT for bank 1 and 2.

Customer: replied 1 year ago.
Stftrm1 0.0
Ltftrm1 -0.7
Stftrm2 0.0
Ltftrm2 0.0
Customer: replied 1 year ago.
That is with codeWithout
Stftrm1 fluctuates 5.4 to - 6.2
Ltftrm1-10.1 doesn't move
stftrm2 also fluctuates from 0 to-5.4
Ltdtrm2 -4.6 doesn't move
Expert:  GM Tech (Cam) replied 1 year ago.

The LTFT 1 is bank one and that being -10 means its sensing to much fuel. Are you sure none of the other injectors are leaking?

Customer: replied 1 year ago.
I'm about to go back through the fuel rail and check
Customer: replied 1 year ago.
7.0 now one has a bad gasket ltftrm1I moved one that I know worked back to 7 and still have the same issue p0307
Customer: replied 1 year ago.
Could my 02 be causing the issue?
Expert:  GM Tech (Cam) replied 1 year ago.

Not usually. The self tests these go through to pass codes would have triggered issues and it would not be showing on just one cylinder.

Back to the cylinder leakage test, did you get that tested yet?

Customer: replied 1 year ago.
Not yet.. That will be tomorrow I guess... I went ahead and did the o2 because it threw that code awhile back.. I've swapped coils/plugs/moved fuel injectors from one to the other, cleaned throttle body,.. What I find odd is fuel pressure while no code is present it is at 44 consistant.. When check engine light hits it jumps to 58.. Any reason.. I've read reports that fuel pump is bad and fixes this issue.. Dont know if you have ever heard of this
Expert:  GM Tech (Cam) replied 1 year ago.

Low fuel pressure does cause misfires and as I mentioned before, 44 psi is low.

Customer: replied 1 year ago.
I'm taking it in for diagnostics today.. I'm at my whits end with it... Going to have them perform the leak down test and look at the fuel pump issue.. In your experience I've read reports of lifter failure.. Would you be able to hear that issue?
Expert:  GM Tech (Cam) replied 1 year ago.

Lifter issues usually don't always make noise, and they usually cause a steady misfire all the time.

Customer: replied 1 year ago.
Well after trying two of everything on cylinder 7 and checking for spark and power to the injector.. I'm pretty sure it's pump or a lifter issue.. How bad is tear down on the intake manifold? Doesn't look overly complicated.. And is this odd that this happens right after fill up... Someone said I might have got too much gas in the tank and got into the evap system.. Idk.. So many things could cause it I guess
Customer: replied 1 year ago.
Well one more thing.. I just sprayed carb clean on cylinder 7 after the truck cooled off.. It sounds like it is sucking in at cylinder 7.. Possible intake leak
Expert:  GM Tech (Cam) replied 1 year ago.

sorry for the delay. Is it around the intake or the injector?

Customer: replied 1 year ago.
Around the intake.. I sprayed lower than the injector.. There was no increase in rpms.. But it was a definite sucking sound
Customer: replied 1 year ago.
Lower manifold
Expert:  GM Tech (Cam) replied 1 year ago.

Are you sure your nearing the PCV system working in that area?

Also with the fuel supply around there, its possible you are hearing that.

Customer: replied 1 year ago.
It's only when I spray the carb clean in the area.. I put the red nozzle down low by the lower intake and sprayed.. I don't think the fuel supply would pick it up
Expert:  GM Tech (Cam) replied 1 year ago.

Then its likely intake gaskets. They are easy enough to change. Lets try a set of those.

Customer: replied 11 months ago.
New intake installed, same issue... Banging my head against the wall!! Took off valve cover to watch the valves open and close when turned by hand.. They function as they should.. No broken valve springs.I replaced map sensor and no code but rough idle when it's left unplugged .. Fuel pressure with key on is 83 then drops to 44 at idle once code pops up fuel goes to 58-61St ftrm1 -1.5 to -7
Ltft 1 -18 to -22.6
Srft 2 3 to -1.5
Ltft -12.5 to -14Map 11 to 9.7And some serious lifter tickingAny new advice??
Customer: replied 11 months ago.
Compression in that cylinder is 120.. (Also a cheap gauge)
Expert:  Gary replied 11 months ago.

Hello David,

Is your engine a AFM (or DOD) engine, V8 that is a V4 on light loads?

If so, P0307 will be a valve not operating, once the engine starts and has oil pressure.

Pull the valve cover off for cylinder 7, crank the engine while it is disabled and you will see all the valves operate.

Now enable the engine, start it up, and one of the Cyl 7 valves will not be operating.

The offending valve lifter has rotated in the lifter guide.

Now you need a camshaft and a full set of lifters.

Engine out, heads off etc.

Gary

Customer: replied 11 months ago.
Wouldn't I lose compression?
Expert:  Gary replied 11 months ago.

No, the valves function normally at cranking speed without oil pressure.

Remove the cover, crank the engine, the valves will be normal.

Once the engine fires up and has oil pressure the offending valve will not be operating.

A good design in theory, plastic guides allow the lifter to rotate, then it is permanent AFM mode for that cylinder.

Gary

Customer: replied 11 months ago.
Can I put the chip in the obd port that disables afm? So the lifter doesn't do that? And for sure it needs a camshaft?
Expert:  Gary replied 11 months ago.

Once a lifter has rotated, the oil pressure port for AFM operation is lined up with the oil gallery. In other words, the VLOM is bypassed.

You cannot do anything external to the engine to eliminate this.

The camshaft may survive, but most times not.

Can you remove the cover, and start the engine, you will see it.

Gary

Customer: replied 11 months ago.
I believe you because I have done everything else... And driving it left that plug with a ton of black carbon on it.. Is changing the cam a required step? How would the cam be effected?
Customer: replied 11 months ago.
Do I also need to change the lower intake..I read this somewhere:. AFM lifters are caused by incorrect VLOM engagement timing. Please replace your VLOM with GM# ***** when replacing you AFM lifters. Repeat failure is likely if this step is skippe
Expert:  Gary replied 11 months ago.

I feel your pain, I've seen this many times now.

The AFM cylinders are 1,4,6 and 7.

There are mnay ways to fix, but the cam is more than likely damaged.

Depends if you to keep the AFM function.

Gary

Customer: replied 11 months ago.
I would love to see it go.. Can you give me both options!
Customer: replied 11 months ago.
Approx how many hours does the book call for for this job?
Expert:  Gary replied 11 months ago.

Yes, there is a revised VLOM.

There are many parts required for this repair.

Sometimes an engine swap is an option.

The engine needs to come out for a strip down.

The roller lifter and cam lobe will be worn from skidding.

Gary

Expert:  Gary replied 11 months ago.

You can fit 16 normal lifters when you do the cam swap.

Customer: replied 11 months ago.
I will probably go back the way that it is.. Do you know approximately how many hours for this job?
Expert:  Gary replied 11 months ago.

I used to quote 20 hours, engine out, strip down, cam bearings, new cam, lifters, head bolts , head reco, etc.

You car or customers car?

Gary

Customer: replied 11 months ago.
My car
Customer: replied 11 months ago.
can't this be done with the engine in the vehicle?.. Pull radiator and grill to her cam out?
Expert:  Gary replied 11 months ago.

You can, but the heads have to come off to replace the lifters.

A cam change only can be done with some rods and magnets to hold the lifters up.

Risky though.

Customer: replied 11 months ago.
No sorry for the confusion.. I'll have to pull heads and remove lifters then cam.. Just asking if this can be done with the engine in the truck
Expert:  Gary replied 11 months ago.

Hi David,

If you feel you have room to torque the head bolts correctly, I would say you can do the whole job in chassis.

Our cars over here are a little more cramped, and torquing head bolts is a pain.

I would replace the camshaft, lifters, lifter guides, head gaskets, head bolts as a must, the usual sundry stuff.

I would also replace the oil pump, because of the regulator valve wearing and sticking open like they do.

Then they have no oil pressure.

If you are doing it yourself, I would keep the AFM function, BUT you must fit everything where it is meant to go, no ifs, buts, or maybes.

The lifter guides are different front to back.

Hope this helps.

Gary

Customer: replied 11 months ago.
Thank you for the tips! I assume by lifter guides they are the plastic pieces the lifters sit in right? Hell I may just call salvage and see if I can get a motor for as much as these parts cost lol
Expert:  Gary replied 11 months ago.

Hi David,

Yes the lifter guides are plastic, you fit the lifters to the guides and then fit them as a pair.

They are fragile with too much flex, and then this is what happens.

I had one with over 350000km with P0304.

Had spark, had injector pulse, removed rocker cover, no inlet valve for Cyl 4 engine running.

Quoted for second hand engine, way cheaper for customer.

I think you could get a complete motor cheaper than all the parts you'll need.

Have you tried running the engine with that cover off?

Gary

Customer: replied 11 months ago.
No not yet.. I will do that tomorrow... I literally have changed everything else that it could possibly be.. I am getting a bunch of lifter noise so I am 100% sure you are right.. I read that once you here that in one of these engines it's just a matter of time before the lifters fail... I will look for a replacement engine.. Parts alone are about 1200.. Do you know what you've seen motors go for?
Expert:  Gary replied 11 months ago.

Parts for us is more expensive, I've seen a new factory cam at $2500.

Might be cheaper now.

A used engine for us is about $4k plus less labour since it is only an engine swap.

Gary

Customer: replied 11 months ago.
Yeah oem stuff is high! I found everything I need to do the job for 1200-1500.. An engine would be 2k but probably easier to swap! Lol
Expert:  Gary replied 11 months ago.

Hi David,

Yes agree.

Gary

Expert:  Gary replied 11 months ago.

Hi David,

Do you need any further help with this?

If you have decided to buy another motor, have you run your existing engine to verify one or both valves on Cylinder 7 aren't operating?

I'd like you to try it, it seems so weird to watch a valve operating and then it stops.

Regards

Gary