I'm having a misfire/stumble with my 07 V-6 during warm-up. It disappears when the engine is fully hot. Presents as a stumble/shake under load. Idles fine when cold and warming up. Seems to only happen as I go into the higher gears under load, and slowly getting more noticeable. I've checked for loose spark plugs. Found #5 very slightly loose, with discolored coil, so I repaced plug and coil, but it didn't help. Anyone seen anything similar?

 

Does the Malfunction Indicator Lamp (MIL) aka Check Engine Light come on? Also did you get the car read for trouble code(s)? Even if the MIL did not come on, there may be pending trouble code(s) stored. If you have trouble code(s), post the actual trouble code numbers.

 

I forgot to mention earlier. I checked and there are no codes, pending or permanent. That's waht makes this really frustrating. BTW, I have 76,000 miles on the car. Bought it at 36K.

 

Then did the MIL come on when the car has the stumble/shake under load? If not, it may not be a misfire; but, something else causing the stumble/shake.

 

No. I've never had the MIL light come on on this car at any time since I've owned it. I'm stumped right now. I thought the possibly bad #5 coil might have been misfiring, but the new one hasn't changed things. Could be something else, yes. It seems to maybe diminish if I have it in "D3" instead of "D", but it's really hard to tell since the motor revs higher then. Haven't come up with any other troubleshooting strategies though.

 

Read page 3 of this November 2007 Honda Service News regarding cold start vibrations, to see if it sounds similar to what you are experiencing.

For most people that had the conditions described in the article, it usually happens at a higher speed.

Honda Service News Nov 2007

 

Thanks. I can't say it's wheel vibration. It happens at low speeds, and its a shudder/sputter feel, not like flat spots on tires. It also happens whether I'm steering around a curve or going straight, so it doesn't seem like it's a CV joint problem.

Although probably unrelated, there is also a very brief, slight rpm surge a few seconds after I start the car cold.

 

Just to rule out the simple stuff; check the engine air filter for restrictions, pinched air filter gasket (letting debris get through), housing properly installed, etc.

 

Make sure the CEL bulb isn't burned out. The CEL will turn on for 2 seconds (then turn off) when you first turn the key ON.

 

CEL is good. I'll have to check the air intake, but not aware of any problems off hand.