2009 Aveo cylinder misfire diagnosis

[Drake314]

Hi all, recently a coolant hose blew on my Aveo a couple of blocks from my home so I managed to make it back, but with the HOLD and check engine lights flashing I scanned it and the results showed a P0304 code. The car had been my mother-in-law's and was recently handed down to my wife with around 79k miles on it.
After replacing the hose, I began to work on the misfire. From info I have on the car the firing order is 1-3-4-2 and after taking the ignition coil pack block off I discovered what looked to be a small oil leak in the third spark plug well from the left. Upon further investigation I discovered that the mother-in-law had the spark plugs changed just once. Info in the owner's manual says they should be changed every 25k not to exceed 36k.
Attached is a picture of what the spark plugs looked like after taking them off and needless to say they are in pretty bad shape. I replaced all 4 spark plugs with Denso PK16TT plugs, which I believe are a bit better, but when turning the car on it still has a constant misfire with the same HOLD and check engine lights flashing and the same P0304 code. The car runs rough and seems to lose power when accelerating. I decided to not even move it or drive until I can pinpoint the problem. My next step is to check the ignition coil pack and then the compression on the engine.
My question is does anybody know or have any experience on testing the coil packs when they are all in one single block like this car has?? I hope if it did go bad it was only the ignition coil pack for cylinder 4 and I also do not know if it is replaceable by itself or if the entire thing would have go be replaced. Regarding the oil leak I figure I will need to replace the valve cover gasket, but I will have to take it one thing at a time.
Any help would be appreciated.

[avguy]

There is a recall on the factory coil pack - do you know if that recall was done for your Aveo?

[Drake314]

No recall for coil pack - only for brake fluid corroding brake module. I checked this website: Keeping You Safe | Safercar | National Highway Traffic Safety Administration (NHTSA)

[EAD15]

Swap out the platinum plugs for copper (cheap, and what came with the car) or iridium plugs and see if that makes a difference. I remember someone posting ages ago that they had misfires when running on platinum only.

[Drake314]

That's an idea however if it was the platinum spark plugs wouldn't it misfire across multiple spark plugs? I keep getting only the P0304 code for cylinder 4 that I've been getting since the beginning.I'm wanting to check the coil pack but it's not as easy as it would be if they were individual because then I would just be able to switch them around and see if the misfire follows that ignition coil pack.

[avguy]

No recall for coil pack ...

http://www.aveoforum.com/forum/f81/r...9-aveos-13419/

[Drake314]

http://www.aveoforum.com/forum/f81/r...9-aveos-13419/

Thanks for the info, I would have thought that the government website I checked would have given me info on this recall. Well I called the local Chevrolet dealer and they told me they had done the work on the car for the recall back in May 2012 so it has been done on it already. That takes that option off the table, now I am back to needing to find out if the ignition coil pack is good or not and how to test it.
I did read through the thread you posted and noticed the info on the recall stated a spark plug number and a new gap measurement of 0.031-0.035 inch. I wonder if this could be making an impact on the car since I gapped the plugs around .41 due to the original specs calling for 0.039-0.043 inch gap? Still I am wondering why it only throws the same code of P0304 that affects only that cylinder.
Thanks again for all the input.

[Drake314]

Problem fixed. Just wanted to give an update that might help someone down the line with the same problem I was having. I did a compression test with a compression test gauge I bought from Amazon for about $24 dollars. Took all spark plugs out, disconnected fuel pump relay in the fuse box, and with the accelerator pressed all the way down I cranked the car with the compression gauge installed in each spark plug well until the needle stopped moving. All came back with 170 psi so I figured the problem was not being caused by a head gasket/valves/pistons or the like. Decided to take a chance and I bought the coil pack from Rockauto.com for about $80. Installed the part and lo and behold the car started running smoothly. Cleared the code and test drove it and problem fixed! Check engine did not come back on and drives like a champ. So glad it wasn't anything more serious or expensive although it is weird that at 80k miles the coil pack would go back. Could have had something to do with the coolant hose bursting, but either way hope this helps anyone having similar issues.

[avguy]

.... it is weird that at 80k miles the coil pack would go ....

If Chevy replaced the coil pack for the recall in 2012, that would make the mileage on the replacement pack much lower than 80K. But perhaps they didn't do the work they were supposed to, which wouldn't be the first time that ever happened. And that would explain the part failing because it (i.e the original pack) was well known to be defective. You might be able to find that out based on the part # of the coil pack you removed. In any case, glad to read it's fixed, and thanks for posting the outcome!

[pbody]

I had the same issue on my 2010 aveo. Mine has 98k and replacing the coil pack fixed the misfire code.