Bad Coil pack replacement?

My 2009 chevy aveo engine seems to be misfiring. I get a P0300 obd2 code (random multiple misfire). It runs rough, and the check engine light flashes. I had the spark plugs replaced - did not help. I just put in a new coil pack and now the engine turns over but won’t start. When I put in the original coil pack, the engine starts but still misfires. Can I assume the new coil pack is bad?

Are you sure it’s the correct replacement part, and was connected correctly? Can you check it with an ohmmeter?

The vendor said it was compatible with my cars model make and year. Autozone shows a compatibility with the new coils part number. It looks very similar. Fits the engine, and has the correct number of pins on the electrical plug, and fits correctly. I am not sure how to test with an ohm meter. I will have to research what leads need to be tested.

Have you considered that the part AutoZone gave you might be a defective used one that has been substituted?

I’m not blaming AutoZone here BUT, they get a fair number of people who will buy a new part and come back for a refund while palming the old part off on AZ. Some people will damage a new part and bring that back in for a refund. Next customer in gets the old defective part…
This has happened to me several times.

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Thanks. I really need to be able to test this coil pack, and determine if it is bad. I have looked at a few youtube videos on how to do that, but they all deal with a different setup. In my situation, my coil pack is all one piece. When I take out the coil pack from the engine it disconnects from all four spark plugs at the same time.

This is what the part looks like:


Maybe I am old fashioned but it seems to me that if the car starts and runs even if badly with the old coil pack but won’t even start with the new one, you have tested it.


I’m just guessing here based on how that gadget works, but there should be around 10,000 ohms from each spark plug side (the metal part that connects to the spark plug top) to one of the 7 pins on the other side. Try that, see what you get. Bench test only, harness connector removed, and no spark plugs connected.

There’s probably an ohms test for the 7 pin side too, if you knew which pin was which. One of the pins would typically be battery power, one ground, and 4 pins would be for the spark trigger signal from the ecm. On some of those there’s an output back to the ecm so it can confirm the spark actually got triggered.

If the connector matches up ok, and the spacing for the spark plugs is correct, I’m w/ OK4450 above, your replacement part is faulty. They contain transistors and if connected up backward for even a second will blow all the transistors.

Yes, I tested for ohm continuity from the coil (where the sparkplug would spark to) to the electrical connector. I get no response on my ohmmeter (which when I touch the two leads together I get a reading, so the ohm meter is working), but no reading from any of the coils to any of the seven pins. The vendor says I have to take a video of all this to get my money back. Hopefully when I get a good ignition coil pack, I will have a smooth running engine.

Sounds like a fly-by-night parts supplier. Did you pay for it on a credit card? The card company may be able to cancel the charges if the supplier does not do right.

Can you get the part from a local parts supplier, maybe even used at a junkyard?

Now do the same test with the other coil pack just to confirm you get a reading…


Yes, I did test continuity on the old coil and it does have continuity. I also got a reply from FlashAuto who sold me the new coil, and was told that if I made a video of the car starting with the old coil, and then show the car not starting after putting the new coil in, they would refund the money. So, that’s what I was doing the past hour. I can put the video on here if anyone wants to see?

Yes, if I could just get a hold of a good loaner ignition coil. It only takes 5 minutes to swap out and in. Then I could determine if the rough engine problem would be solved, or if it is something else, like maybe fuel related. But most info I have found indicates that the ignition coil will fix the problem.

Sheesh, seems like something they hope you will just go away. How is that any better than a short video of the ohm-meter readings between the two? Still seems like a lot to ask. Compare that to a recent experience I had where they said, sorry for your trouble we have shipped a replacement overnight- no need to send back the defective one…

Since I took the effort to make the video, I thought I would include it here. The file was too big to send it to the email that FlashAuto game to me, so I put it on my daughter’s youtube account. I sent the youtube link in my email to FlashAuto. I wonder what they will think about it being out on youtube for everyone to see. Maybe, they will hurry and get back to me. Anyway, here is the link. I didn’t make another video to show ohm testing. I’ll have to wait and see if they want it too.

Just an update. I ordered a new ignition coil pack off amazon prime. Came in two days. Took me 5 minutes to install, and it fixed the rough running engine. The first coil pack I bought was definitely bad. They agreed to refund my money after the video I made and putting it on youtube. I was about to give up, but it was worth another $60 to finally get it fixed.


Good for you!
Thanks for updating us, and all future readers. :slight_smile:

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Just over a month now, and the new ignition coil is bad. Check engine light flashing and obd code of p0300 again. Also, getting an error code indicating a bad after cat oxygen sensor. The Pep Boys mechanic, who took the readings said he thinks my 02 sensor could be causing the ignition coil misfiring, and thought I should replace it first. How bad is it to drive the car on 3 cylinders? It would seem to me the only danger might be the catalytic converter getting over worked trying to burn the extra fuel.

Spark plug problems, especially if the gap is too wide, can damage the coils. YOu may need to use a shop who has the Chevy specific scan too. With that they can probably do a test to prove or disprove the idea that the O2 sensor is the problem. Misfires can definitely damage a cat, if the misfire is caused by an ignition system or compression problem. A proper firings involves

  • good spark
  • at the right time
  • with the proper air/fuel mixture
  • good compression
  • good flow through the exhaust system

So you’ve got something wrong with one or more of those. the big clue you have is that the misfires are happening on all cylinders, so whatever is going on has to be a problem that affects all cylinders, rather than just one.

  • problematic fuel pressure
  • ignition module problem
  • exhaust system clogged
  • all cylinders have low compression
    etc etc

The dealership replaced the spark plugs 6 weeks ago on a recall for that year and make of vehicle (but, that didn’t help). When I replaced the ignition coil pack 1 month ago the misfiring stopped. And now it is happening again. Is something damaging my ignition coil pack (all one unit on this vehicle. There are no spark plug wires)?