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Mis-firing Honda Element

I own a 2006 Honda Element with 140,000 miles. I periodically get an engine warning light which has been determined to be due to a mis-firing cylinder. I have new spark plugs in it and have moved ignition coils with no change in the mis-firing cylinder.



We are now looking at a fuel system cleaning, moving fuel injectors, or a valve job to troubleshoot or fix this issue.



Unfortunately the mis-firing does not occur consistently so showing the mechanic has been hard.



Are we heading in the right direction and does anyone have ideas here? Have you seen this before?

Is this coil on plug so that moving a coil is also moving the wire, such that it is?

I would check the compression.

If the compression is good then I’d swap the injectors around to see what happens.

Have you ever had the valves adjusted? See what your manual says about valve adjustment intervals. Valves out of adjustment can cause misfiring and can eventually cause valve damage.

We did move coils but I cannot move the wires. So a fault in the wiring would remain with that cylinder.

I will look into that.

You’re on the right path.

You’ve changed the plugs and switched around the coil sticks, which is more that most people tend to do.

Since the issue stays with the same cylinder(s), then its either going to be an internal cylinder issue, or the wires that feed the ignition coil for that cylinder.

Compression test, leak down test, and valve clearance tests are going to be the next steps.
Compression test will show condition of rings and cylinder walls. Blow by, if excessive, would throw off the ignition of that cylinder.
Leak down test would determine if the compression is escaping past the valves or the rings, pointing if its a head only job, or a re-ring job.
Valve clearance will tell you if anything needs to come apart at all.

I would check the valve clearance first, making sure it is in spec.
Then do the compressions and leak down tests.
There really isn’t any point doing the leak down and compression tests first, then checking the valve clearance, making adjustments, and then redoing the leak down and compression tests again. This will save some time and effort.

BC.