stevetro1

Hi - working on a 2007 Suburban LT.

As many others, I'm currently troubleshooting a P0307 code along with rough idle and several stabilitrak messages.

I replaced all plugs and wires and swapped coils around, and the problem remains at cylinder 7. When changing plugs and also looking at new plugs after a few miles, I see that cylinder 7 plug's ground electrode is covered in oil but the center and cone are clean. All other plugs are clean.

I also noticed that AFM appears stuck in V8 mode (as indicated by dash info center message) - never moves around to other cylinder counts. So I'm not sure if this is a cause or a symptom as well.

In 3rd gear+ and 40mph+ the car drives nice and smooth. I also checked compression in cylinders 2,4,6,8 and they are all between 125-140 (cyl7=135) - Please keep in mind that I was using a basic Harbor Freight tester so maybe my numbers are lower than reality but they are fairly consistent.

Today I will check fuel pressure - Should the number be different when the key is just on Vs the car running?

This is my second engine with the first one replaced under warranty due to mis-behaving AFM oil flow and oil consumption. This engine now has about 90K on it just around where the first one was replaced, but oil consumption is not a big problem.

I just want to make sure I'm gathering enough intel before I see my dealer in 5 days for scheduled appt.

I've heard about AFM solenoids, stuck exhaust valves, and injector problems so I'm not sure exactly where my symptoms should lead me?

The other question is what is so special about cylinder 7 that it is commonly referred to with a P0307 for many different issues?

Any help is greatly appreciated!!

in2pro

cylinder pressure won't be the same for all 8, you are looking for similar pressure across all 8 and it looks like you have that if I read that correctly....

Might also want to consider walking the injector if you have not already....

Fuel pressure should be 60+ and steady while running, it should hold for several minutes after key off....

therewolf

Hi stevetro1, Welcome to the Chevy Forums.

Is Cyl#7, by chance hard to access?

Because many times flat rate mechanics will simply

ignore the hardest plug to replace on a V8 engine,

especially if it is under a bracket, or blocked by

the A/C compressor.

stevetro1

Driver side is pretty easy to reach, passenger side is another story with Cylinder 8 being a real bitch. I just did these all myself - cut arms and all!

I read elsewhere that cylinder 7 is the last injector to get fed fuel and is a likely a collection point for crud. I would like to check it out but it looks like the fuel rail removal and injector removal might be a bit beyond me since the surrounding disconnects might be a little intimidating.

Is there a shortcut way of getting the injector out or does whole fuel rail need removal? I've taken them out on easy to reach foreign 4 cylinders - much easier.

Sergio Lisboa Machado

Hi, have you inspected the fuel injector, maybe it is not closing properly and it keeps dropping fuel when it is not necessary.

stevetro1

I did not have the correct fitting for the GM fuel rail to check fuel pressure, so not sure about it. Get good spark at cylinder 7, but new plug looks absolutely unused after many miles, so it must not be getting fuel. I'm really thinking injectors are a problem so I will get to that.

Does anyone believe that a saturated vapor canister and faulty vapor solenoid could cause similar misfire issues? I know that crud could have released from the canister but it looks like the fuel filter is built-in with the pump and is "supposed to be lifetime"

I believe my canister is saturated as I removed it and very oily goo dripped out - not alot only a few drips - not sure if that is normal or not, but the canister and solenoid are going to be replaced tonight. I received the solenoid code months ago and never put the part in that I ordered.

Thanks!

Skygun

As far as pressure goes, O’Reilly's have a free fuel pressure gage to use. Idrove there and checked mine in the parking lot. Expect a bit of fuel spillage so bring a rag

You can get a stethoscope from Harbor Freight ($1.99) and check each FI.Just run the engine and touch the scope's tip to the injector. You should hearthe actuator value working.<o></o>

That is extent of knowledge for this issue; I am dealing with a high fuelratio on my 07 burb, but still can’t find the reason for it.<o></o>