Idles rough and runs jerkily They told me it shows 6 plugs misfiring?

Tiny
EUSGRRE
  • MEMBER
  • 2004 HONDA ODYSSEY
I have an engine light on on my Honda Odyssey. I took to an auto parts place where they checked for me the reason code for the engine light. They told me it shows 6 plugs misfiring. I replaced all 6 plugs and the engine light went off and seemed fine for a while. A few days later the engine light returned and now started to idle rough for a short while after starting. I returned to the auto parts for another reading of the scanner. This time they said it showed all 6 coils were misfiring. I'm not sure how to interpret this. How could all 6 coils go bad. In addition the engine now runs rough for a longer period and pulls back when driving. I left the vehicle down for a while to determine how to proceed. Also I've noticed that my coolant level in the reservoir have dropped a couple time within 3 months. This was 1 prior to all these problems and once after started having these problems. I dont know if this is related but it seems there is a leak but I cannot see a leak on the floor of my garage, so not sure where its leaking out.
Note: If I leave the engine running for a while, the rough idling smoothes out but I have the pull backs and jerking when attempting to drive it.
Friday, September 10th, 2010 AT 11:01 AM

1 Reply

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
You are correct. All 6 coils do not go bad at the same time. Plus, there are no codes for just the coil unless they are circuit codes.

If you have misfires on all cylinders, then we need to check the things that affect all cylinders which are air and fuel.

If you changed the plugs and the light went off and then came back on, I suspect the plugs are fouled and replacing them got the engine running well again. Now they are starting to foul again.

This means we need to start with checking for a vacuum leak and then the fuel pressure.

Here are guides that will help with doing both of these:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Basically, we need to find out what both of these systems are doing and then pull the plugs again.

Here is a chart that will help with finding out if the plugs are fouled or not.

Please run through this info and let us know what you find.

Thanks
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Thursday, December 23rd, 2021 AT 3:45 PM

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