Greetings Honda Gurus,

I work on Nissans but this is my personal car -- 06 Honda Accord J30A5/6MT sedan. Problem is a very rough high idle on cold start, and a very rough idle at any temperature right around 1000 RPM. Ran BG44K injector cleaner, pulled front bank plugs -- normal color and proper gap. Car has 38000 miles. Throttle body cleaned 3K ago. Oil changes every 7.5K with Royal Purple 5W20. In generic OBDII mode, st/lt fuel trims look ok +-1%, cam/crank sync, o2 sensors are switching, MIL is off and no codes stored, misfire counters on all cylinders stay at 0. This vehicle is equipped with EGR. Have not attempted to test operation of EGR system yet. Performanceseems strong, especially top end. However, the rough idle is annoying and you can really feel it vs. other V6 hondas. The car does get driven pretty hard and regularly runs up into the VTEC but is not powershifted, clutch-dropped or otherwise tortured. According to my local Honda dealer there are no ECM reprogram updates for this car and no TSBs for idle issues. Gas used is 93 octane Chevron or Mobil. Another thing I've noticed is that the idle undershoots a bit when A/C comes on now, sometimes down to almost 500 RPM before the ECM compensates. I do run a sound system (2x12 @ 800w) but has a 1 farad cap inline and battery/alternator check out.

Do these engines need valve adjustments like the 4-bangers do? I have noticed a louder ticking noise coming from underhood (especially in garages or near walls) and thought it may just be the injector seats getting worn from the 15% ethanol in the gas, but could it instead be a sign of valve adjustment issues? Any suggestions from Honda pros before I pull the front bank valve cover and inspect? I've also noticed that if I put the clutch in, the rough idle smooths out a little bit, so I looked through the clutch inspection cover and there wasn't signs of lots of dust or burning, and plenty of disc material left above the rivets. Could this also be related to a pressure plate or flywheel issue that I can't see? Any other suggestions/ideas on cause of rough idle?

 

The EGR system doesn't operate until the ECU sees full operating temp.
Though it could be a EGR valve sticking open a little bit, usually you get a 'lift sensor' code.
The one thing that comes to mind is the IACV is hanging open, try unpluging it to see if the idle drops a couple hundred RPM.
Also you want to be sure there is a little slack in the throttle cable, if it is too tight and opens the throttle plate too much air is getting in, and the TPS reading will cause the ECU to advance timing.
When you have your scan tool hooked up can you look at both primary O2 sensors and see if there might be a lean burn?

The V-6 does not need valve adjustments.

 

Thanks for the suggestions honda -- I will try that tonight when I get home with the IACV.

Scan tool will have to wait until I get back to work on Monday, I can read generic info with it but not honda-specific info.

 

I thought honda recomended valve adjustments at 105,000 miles?