2007

Well, here's an update and not happy to say it is good. After changing the plugs to proper ones as above (and the manual says the same thing), I still have the code p0303 #3 misfire. I cleared the code today and about 15 miles later it came back on after the transmission shifted hard at 1-2 and 2-3 shift. So tomorrow I will check the code again. Just a little bummed out about it all.

whopper

Swap coils between #3 and #1 cyl, and see if the problem follows the coil. You eliminated the plugs as the cause, so try the coils next.

donbrew

and then injectors.

2007

Thanks for all that have replied back. After swapping coils 2 & 3, the problem still existed. So I did swap the injectors as well( 2,3) and still getting p0303 cylinder #3 misfire.

So anybody have a clue what I should check next or do I have to take my car to a repair shop?

Thanks

whopper

Yeah, I think you have exhausted possibilities here - it might be a problem with loose valve guides, head gasket etc..

donbrew

Sound like it's an internal problem. Can you perform a leak down test, or a compression test? If not then you need professional help, at least for diagnosing definitely for fixing.

2007

Thanks for the reply. How can I have an internal problem with only 73000 miles. I thought these engines should last like to maybe 200,000 miles?

After checking the code today before my last post, I did not clear it on purpose. So, after some errands the CEL turned off by itself and so far so good.

But I know it will come back again.

As for compression test, Yes I can do that. Never done it with fuel injected engines. Only carbed. Should I unplug wiring from injectors and coils before I check compression?

Thanks again, I can't afford to blow money right now at a shop, so I'm more than willing to try and fix it myself.

843de

You should pull the fuel pump fuse (#13) and the ECM fuse (#41) in the underhood fuse box, then have a helper hold the gas pedal to the floor to initiate the "Clear Flood" mode while cranking the engine.

A healthy Ecotec should have between 155-180psi in each cylinder on a compression test, GM specs state that there should not be more than a 70% variation between the highest and lowest cylinder.

If you find that cylinder 3 shows 100psi or less, that's a fairly good indicator of an issue with the valve seat, valve, or valve guide.

There were problems on some 2007's with loose valve guides for which GM issued a TSB but no recall.

A cylinder leakdown test might also be next on your list, plus picking up a coolant test kit to check for products of combustion in the coolant.

donbrew

They can have bad valve guides and/or blown gaskets. Use the search tool, you will find a couple low mileage failures.

Low mileage/year does not guarantee anything.

You MUST disconnect the coils if you are going to remove spark plugs. (slapping ones forehead immediately after reading what one just typed and realizing the folly). That is light hearted, please don't get all that.

2007

Hello everybody!!

Well after a long hard cold winter, i finally came around to doing a compression test on my 2007 2.2l auto w/76575 miles.

I'm still having idle issues of running rough, CEL comes on and off on a regular basis(5 days on, 3 off, then 7 on , 10 off and so on), Currently been off for 7 days.

I've read alot about the common burnt valve issue so I did a compression check to see where this engine is at, results are:

#1 - 180 PSI
#2 - 165 PSI
#3 - 100 PSI
#4 - 140 PSI

I going to assume that the cylinder head is bad. I have no loss of coolant to rule out head gasket. I've done 2 sets of plugs, swap coils and injectors with no clear signs of improving.

I've also done the SeaFoam treatment about a month ago. Nothing noticable to say about that.

I guess its now time to research on head replacement.