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Gary
Gary, ASE Certified Technician
Category: Chevy
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Experience:  Senior Technician
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2007 chevy cobalt 2.2 ecotec. recently had valves repaired.

Customer Question

2007 chevy cobalt 2.2 ecotec. recently had valves repaired. cyl #1 had cracked exhaust valve. upon dissasembly i noticed the ex and in timing marks were on the incorrect cams. possibly a manufacturing defect?
Submitted: 7 months ago.
Category: Chevy
Customer: replied 7 months ago.
ok. just to clarify, according to alldata the intake cam marker should be at 2 oclock, and the exhaust mark should be at 10 oclock. what i discovered was the intake cam had "exh" mark at 2 oclock and the exhaust cam had "int" mark at 10 oclock.
Expert:  Gary replied 7 months ago.

Is the engine running like that?

Customer: replied 7 months ago.
it runs. but it keeps popping code. P0016 cmp cnk correlation code. ive checked and double checked the timing. it is on tdcc cyl #1. "rotate engine over, intake valve opens then closes then piston to top".
Expert:  Gary replied 7 months ago.

Sounds like the camshafts are swapped over to me, hence why the marks are wrong.

Engine will run but cam sensor lug is in wrong place.

Gary

Customer: replied 7 months ago.
initially what i thought as well. but the intake and exhaust cams cannot be swapped. the intake cam is longer than the exhaust because of the "lug" as you call it. the exhaust cam is significantly shorter.
Customer: replied 7 months ago.
i also did some reading on ecotec forums that the ecotec 2.2 has had some issues with the chain tensioner not properly holding tension. i replaced the tensioner with the updated "snap ring" style tensioner. i have put my head together with our other mechanic here at the shop, i have suggested the chain may be stretched. but our other mechanic doesnt think this little 4 cylinder has enough horse power to stretch a chain. i did notice the sliders look almost brand new. no wear on them whatsoever. after reading more and more about the 2.2 ive seen that the timing system on this motor is under engineered. very simple and "flimsy".
Expert:  Gary replied 7 months ago.

Ah yes, I forgot about that.

Are you setting the timing where it should be, or where you think it should be?

In other words, TDC 1, inlet and exhaust closed, TDC 4, inlet and exhaust on overlap.

And then the marks are wrong?

How about No. 1 on overlap, and No 4 on compression, valves closed.

It is the only thing it can be now, since the engine runs at the moment.

And yes, they are a bad design in many aspects.

Gary

Expert:  Gary replied 7 months ago.

I would say it must be out by one tooth.

The engine must be on overlap No. 1, not compression as one might think.

I would have put all of the correct marks would they should be, the 3 links of the chain lined up, and then the timing would be correct.

I would say timing cover off now to retime the cams.

Gary

Expert:  Gary replied 6 months ago.

Hi again,

Do you need any further help?

I hope my advice has been of assistance to you.

Kind regards

Gary

Customer: replied 6 months ago.
we decided to put a timing chain kit on it and meticulously put it back together. alldata and all other informational sites say to correctly time the motor it needs to be at top dead center compression #1 i am not very comfortable with tdcc #4 as you recomend. after all it is an interference head. we cant afford to pay for another head job on this vehicle.
Expert:  Gary replied 6 months ago.

Hi again,

If you think about it, the short block has 1 and 4 both at TDC.

It does not matter which way they would be timed whether to 1 or 4.

The PCM knows which cylinder is on compression from the cam signal.

You originally mentioned you thought the wheels were swapped.

I will check on GM SI again for you.

Gary

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