Utilized search box for VCM related posts and didn't see any, combed through 4 or 5 pages, no dice... so had to post this .. .

2008 Accord V6 with the VCM engine, automatic, 170k mi., bought it from an auction, looking to keep it. The vehicle runs great when I disconnect the coolant temperature sensor, but when I reconnect it, between 1500-2000 rpm, the vehicle bucks like a bronco, then smooths out. Going up moderate inclines or hills, it'll do the same thing. It feels like it's hunting between 2nd and 3rd gear, like an older vehicle with bad vacuum lines. At speeds above 50mph or so, there's never any shudder. Already replaced the coolant temperature sensor at the top radiator hose housing and air filter, because it needed it. The throttle body plate looks spotless. Ordered two of those VCM muzzles, neither one worked. Ruling out the transmission and spark plugs, since it runs great with the harness unplugged. The airflow meter is a Hitachi product and looks practically new, again, ruling it out because the vehicle runs great w/ temp sensor unplugged.. The oil level is fine, haven't looked at the spark plugs, there's no check engine light. I haven't looked at fuel trim etc. ... What would you guys check? Not taking it to the dealer, used to work at dealerships, so I know better. I don't know the VCM system well, I'm sure there are cam sensors involved, read something about sound feedback through speakers, Honda made all of this fuss to save 1-2 mpg? ... Anyhoo, looking for advice from DIYers whom have solved this issue with a vcm V6 between 2008-2012... thanks in advance ...

 

VCM??
Isn't that the vehicle control module?
Two in a vehicle?
One is the ECM engine control module?
And the other is the TCM transmission control module?

Or is it some thing totally different?
Don't know.

 

variable cylinder management

 

Thanks. So, using oil to push pins into locking or unlocking the cams
This engages or disengages the cylinder.

This just makes me wonder what that has to do with the engine coolant temperature sensor?
From what you say, it sounds like the wires to or from the coolant temp sensor is shorted to an engine management control line
Cause when disconnected the engine runs fine

Can you follow the coolant sensor wire to see if there is rub through and/or fray??

 

thanks for the reply, avi. i haven't followed the line, will do so, today. also, after resetting the cel (from disconnecting the coolant temp sensor line) i took the vehicle for a freeway test drive. i noticed that upon braking from freeway speeds to a stop, for a brief 1-3 seconds, the battery warning light comes on (the square with +/- symbols)... then goes back off... battery warning light will not flicker when coming to a stop at surface street speeds... will check serpentine belt tension...

scanned vehicle and got a warning within the brake module that reads "ABS/VSA control unit quit communication above 30 mph" ...
i get two fault codes within the module, 61-1 Modular Control Unit Initial IG Low Voltage and 83-19 ECM/PCM Relation Failure ...
looked up causes for the battery warning light flashing off and on, and the electronic load detector also came up as a suspect...
at idle, with live data, the alternator reads 54%, as i press the accelerator, the value drops, progressively into the low 30 percentile
the battery voltage reads 13.5 and pretty much stays there ...

will check battery and alternator with a multimeter as well, of course will also examine the wires from the coolant temperature sensor, as you suggested...

 

Sounds like you got a plan
Good luck

Let us know how it goes

 

update: went for road test with live data ... ELD output was between 1.2 to 2.2 volts, most of the time... and the battery voltage was between 13.4 to 13.6 volts ... is this normal? 100 degrees in vegas, with nav, ac, and headlights on ... are these normal readings? ... it's a loaded 08 honda accord 3.5 v6 vcm engine automatic, ex-l sedan... again, my issue is violent shudders between 1500-2500 rpm, up to around 45-50 mph... when i disconnect the coolant temperature sensor harness, the car runs perfectly... can it be a bad alternator voltage regulator or ELD? (electronic load detector in fuse box)

cleared VSA/ABS fault codes (with a better scanner) before road test, they didn't return, no flickering battery warning light... previously, i cleared codes with a generic bluetooth device that couldn't go into the abs module, so the code might have been lingering from when i pulled the harness off the coolant temp sensor ...

 

I don't see anything wrong.
Battery voltage is really alternator voltage
Engine running and loads on (AC, headlights,etc) 13.4 to 13.6 volts is good enough

As far as I can see, it has to be some thing connected to the engine temp sensor
Wish I had a schematic

 

changed the oil (full synthetic 5-20) and noticed it ran perfectly for about 15 minutes, then started shuttering again (after heating up)... in D3, absolutely no shuddering, perfectly smooth ... changing the plugs, a couple look questionable (probably won't make a difference)... the shudder feels like a manual vehicle when it's in 5th gear at 20 mph... wondering if it's a code issue, there is a tsb for vcm reprogramming .. will call dealer tomorrow and update