Topic: Random misfires (P0300) - variable cam timing ??

[Chemist]

Chemist, do you have an aftermarket flywheel?

I do not.

As Critterman stated, I do have the DDM S/C but have 34K miles with it before any of this started. I'm going to try to get a good hour with the garage owner next week and see if we can nail this down. I'm in favor of starting at the intake filter and working our way back to the block. My son-in-law, a Master Auto Tech for Toyota has given me some new places to look. I've got to do some more reading to determine exactly how our VVT operates so I can communicate with the garage with an educated perspective. Regardless, as always, I appreciate your input.

Merry Christmas to all!

[Jackknife]

I do not.

As Critterman stated, I do have the DDM S/C but have 34K miles with it before any of this started. I'm going to try to get a good hour with the garage owner next week and see if we can nail this down. I'm in favor of starting at the intake filter and working our way back to the block. My son-in-law, a Master Auto Tech for Toyota has given me some new places to look. I've got to do some more reading to determine exactly how our VVT operates so I can communicate with the garage with an educated perspective. Regardless, as always, I appreciate your input.

Merry Christmas to all!

Byron, have you actually removed and inspected your aftermarket cat?

[Brad Kenny]

Hoping that this new look at the car will turn out something more than just another unknown. It is a shame to see such a nice vehicle sidelined by such a problem. Best of luck and hope the issue is found soon.

[Arabas]

Chemist, i was reading the bulletin spider posted. when you turn the A/C on and step on it, do you have misfires?

[Chemist]

Byron, have you actually removed and inspected your aftermarket cat?

Jack,

This is expressly on my list of "have you done this?" for the garage owner next week when I get back to Lubbock.

Thanks.

--Chemist

[Sol Asylum]

Have them visually check the cams and make sure there are no flat lobes.  Having a wore out cam can cause some unique issues with the VVT.  At some point I will let you all know how I know this.

[Gentleman Jack]

Have them visually check the cams and make sure there are no flat lobes.  Having a wore out cam can cause some unique issues with the VVT.  At some point I will let you all know how I know this.

Gee SA, we are on the edge of our seats....YAWN. 

[Sol Asylum]

GJ I was waiting until I got my car back and was able to get some pictures of the cams.

I was having an intermittent problem with my new G6 where after start up the engine would run rough and then the traction control and stability control would turn off.  I took it in and they scanned it and said it was a bad coil pack and spark plug so they replaced them.  The next day same issue, so I took it back.  This time they said it was missing on all but one cylinder.  After further looking they found that the cams on the back side of the engine (its a V6) were no good, I was told they had some flat lobes.  A week later they said they finally had it all back together so I picked it up this afternoon.

Here are some pictures of the cams.
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Looks like an oil problem to me because rust shouldn't be forming like that, engine only has 10k miles on it. 

The dealer told me that according to GM tech this is only the third reported case of this happening on the 3.6 VVT V6 engine, lucky me.

So if this was in fact the cause of the problem it shows that a cam that isn't up to par can cause other problems that you otherwise wouldn't expect on a VVT engine.

[Critterman]

That kinda sucks, no it actually does suck.  Did you ask them about an oiling issue, or is the rust from when they had them out laying around the shop waiting for the new ones?

[Chemist]

Spent an hour with the shop owner today.

1) Timing chain is good. Timing (as evidenced by misfires) still seems to be bad.
2) Actuator is producing the requested variance in cam rotation (or is lying about it to the sensor).
3) No one knows what the root cause of the misfires is. Hoping to borrow a friend's to get some comparison data.

Oh, well...

[Jackknife]

Spent an hour with the shop owner today.

1) Timing chain is good. Timing (as evidenced by misfires) still seems to be bad.
2) Actuator is producing the requested variance in cam rotation (or is lying about it to the sensor).
3) No one knows what the root cause of the misfires is. Hoping to borrow a friend's to get some comparison data.

Oh, well...

And the cat is.....?!!

[Chemist]

The cat appears to be fine. When I get the car above 3000 RPM, all is well. When the VVT is deactivated, all is well. I don't think the problem is the cat. I will know more on Monday, Lord willing.

[1KULSOL]

The cat appears to be fine. When I get the car above 3000 RPM, all is well. When the VVT is deactivated, all is well. I don't think the problem is the cat. I will know more on Monday, Lord willing.

Byron,
I know this has been a long struggle trying to determine the root cause of the problem .... hopefully the problem will reveal itself Monday ... from all the things you've checked I somehow think it has something to do with the computer  ... but what do I know  .... Good Luck ...

[Chemist]

Mike,

I keep thinking the same thing, but we'll see Monday, I hope and pray.

--Byron

[Critterman]

Do you have a spare computer?  Can you get one?

[Chemist]

Do you have a spare computer?  Can you get one?

I do, but it has a locked custom N/A tune on it. I'm going to try to ship it back and get it back to stock.

[Graywolf]

When they checked the timing chain, did they take it off. A new chain appears erect when turned sideways. A strechted out chain will look limp when turned side ways. Interesting about lighter flywheel setting off a code since I have a fidanza flywheel,neutral balance shafts and custom built ATI damper. My chain was strechted out ,so I replaced it However my car has not been driven more than 200ft since that was done and won;t be driven until spring. My car is topless,

[Chemist]

They have not removed the timing chain. All marks line up (by their trained inspection and my un-trained one ).

More info tomorrow, Lord willing. I'm off to bed.

[Critterman]

Sounds like a Vector Tune, they unlocked mine without a problem and reverted it to stock

[smartin]

I do, but it has a locked custom N/A tune on it. I'm going to try to ship it back and get it back to stock.

I can get you in touch with Chris White if you need me to from Vector.

[NormSky]

Anybody at Vector can help you.  I sent in another ecm with VIN and they'll flash it back to stock for aroung $55. I through in an extra $10 for shipping and it gets turned around quick.

[Chemist]

Thanks, all. I've already been in contact with the fine folks at Vector.

[1KULSOL]

Thanks, all. I've already been in contact with the fine folks at Vector.

Byron,
you could have Vector ship it to DDM and they could flash their tune on it so you would be set to go ... just a thought.

Mike

[Chemist]

Byron,
you could have Vector ship it to DDM and they could flash their tune on it so you would be set to go ... just a thought.

Mike

Actually, I'm wanting a pure stock ECM to make sure it's not my present tune/ECM giving me grief.

RC is letting them scope his car tomorrow to see if/where we differ. I'm also going to have them look at the EVAP purge valve solenoid a la Arabas.

[Arabas]

Chemist, since you are at that point, why don't you have them clean your maf and maps? it's a no cost and easy thing to do, just for the sake of it.