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Discussion Starter · #1 ·
2006 EX-L NAV, just under 215 kmi. Starting in mid-August, I am getting an intermittent cylinder 6 misfire when the engine is cold. I can feel the engine running rough for about 30-45 seconds while the CEL blinks (sometimes VTM-4 comes on, too), then after it has run for a bit (less than a minute), it smooths out, the CEL is in solid and can be cleared. Once the engine is warm there are no issues. Gas mileage has gone down a bit (its in the high 15's) but the car sees almost 100% city driving.

Steps taken:
  • Swapped #6 coil pack with another. Fault stayed at cylinder 6.
  • Replaced spark plugs with Honda OEM
  • Tonight I dumped a bottle of SeaFoam high mileage in a quarter-tank of gas to try and clean it out

This issue cropped up last year (always cylinder 6 misfire with occasional VTM-4). I had the valves adjusted -> no effect. Eventually I replaced all the coil packs with Honda parts and the problem went away. But now it is back.

Part of me is thinking that something is leaking by when I have cold metal, but seals itself after it expands from heat. But it clears up so fast that I don't think the engine has had a chance to appreciably heat-up.

I'm trying to fix this on the cheap (if possible) because I am still looking at a timing belt replacement and a new set of tires. I do have the service manual can wrench - might take me a lot longer but I can do it.

Any thoughts?

Pete
 

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2006 EX-L NAV, just under 215 kmi. Starting in mid-August, I am getting an intermittent cylinder 6 misfire when the engine is cold. I can feel the engine running rough for about 30-45 seconds while the CEL blinks (sometimes VTM-4 comes on, too), then after it has run for a bit (less than a minute), it smooths out, the CEL is in solid and can be cleared. Once the engine is warm there are no issues. Gas mileage has gone down a bit (its in the high 15's) but the car sees almost 100% city driving.

Steps taken:
  • Swapped #6 coil pack with another. Fault stayed at cylinder 6.
  • Replaced spark plugs with Honda OEM
  • Tonight I dumped a bottle of SeaFoam high mileage in a quarter-tank of gas to try and clean it out
This issue cropped up last year (always cylinder 6 misfire with occasional VTM-4). I had the valves adjusted -> no effect. Eventually I replaced all the coil packs with Honda parts and the problem went away. But now it is back.

Part of me is thinking that something is leaking by when I have cold metal, but seals itself after it expands from heat. But it clears up so fast that I don't think the engine has had a chance to appreciably heat-up.

I'm trying to fix this on the cheap (if possible) because I am still looking at a timing belt replacement and a new set of tires. I do have the service manual can wrench - might take me a lot longer but I can do it.

Any thoughts?

Pete
Examining the spark plug for signs of fouling can give you some indication. If you know your coil and spark plug are good, then fuel air mixture becomes the concern. Possibly a bad injector or I hate to say, low compression. You might do a compression test on that cylinder.
 

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Discussion Starter · #3 ·
Thanks for the reply. Do you think I should do a compression check on all cylinders? Or since the only issue I have had has been on cylinder 6, is ok to just do that one?
 

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Thanks for the reply. Do you think I should do a compression check on all cylinders? Or since the only issue I have had has been on cylinder 6, is ok to just do that one?
#6 for sure, but yes, by doing the all, it will give you a full picture.
With the engine running, have you pulled #6 coil to see if the engine runs worse or no change?
 

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Discussion Starter · #5 ·
So what is the best way to disable the fuel system for the compression check? I don't have the Honda Diagnostic System to turn off the injectors. Should I just pull the fuse for the fuel pump, or should I include the ones for the coils / plugs as well?
 

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So what is the best way to disable the fuel system for the compression check? I don't have the Honda Diagnostic System to turn off the injectors. Should I just pull the fuse for the fuel pump, or should I include the ones for the coils / plugs as well?
We always renoved all the coils and plugs. Never worried about the fuel. I see no harm in pulling the fuse to the fuel pump too. Sounds like a good idea.
 
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