I have a 2008 Ridgeline. Check engine light on. Also causes VTM-4 light to come on. Runs rough. Replaced spark plugs and coil packs. No change.

 

How many miles on it?
What was the condition of the plugs when you pulled out the old ones?
What is your maintenance history?
What codes are being thrown?
What is the color and smell of the tranny fluid and coolant?
Did the CEL and VTM-4 light and rough running appear all at the same time? (right after refueling....bad gas?)

 

Sorry for late response. I had to wait a few days to use the forum. My Ridgeline has 160,000 on it. Plugs seemed fine. I do not know the maintenance history except for what I have done (mentioned above).
Codes were - 0300 - random misfire
0301,0302,0303,0304,0305,0306 - all misfires on specific cylinders.
Also, codes for running to rich.
Coolant looked and smelled fine. Didn't check transfluid.
Sometimes the VTM-4 light comes on and sometimes it doesn't. If I drive it far enough it will eventually come on.
I have taken to 2 different mechanics because I didn't have the time to keep it off the road for me to work on it. Both mechanics were unable to fix!
I live in a small town.

 

Timing belt and valve adjustment
Dirty worn out AFR sensor
Dirty MAF sensor

 

ok,thanks! I cleaned MAF and have already changed the timing belt. I have it where it starts off with only #1 misfire, but then other cylinders show misfire after short period of time. I would guess I want to start with rear upper AFR sensor next?
I really hope I don't have to do a valve job. It has been many years since I have done one! I appreciate the advice. Let you know.

 

You could do a compression test and a leak down test to determine if a valve job is necessary. that being said, they are recommended at predetermined intervals and it where you say it has been hears, it could be time.

 

Not valve job, valve lash adjustment.

Usually the exhaust valves get tight and when hot the valves will not seat fully, this will cause loss of compression and misfires to happen.
Check your valve lash adjustment with the engine cold. This will require removal of the upper plenum(intake) and the valve covers.
Pretty easy to do. Just a bit time consuming ~3-4hrs if it is your first time on a J series V6.