[rpaoness]

I have a 2001 GMC K2500HD w/ 6.6Dmax / Allison that I purchased in May - 151k mi, all 8 injectors replaced in '04 at about 90k mi according to GM service history.

CT emissions require a "snap" test, which is a test that accelerates the engine (in park) at full throttle until it reaches the speed governor, holds for 1-4 sec, and then releases. This is to be repeated 3 times before a "real" test, and then it can be tested several times after. According to my last test, they performed 9 "snaps", and the truck scored 47% opacity which is above the 40% permitted.

I've only put about 1000 mi on the truck since purchasing (stupid fuel prices), and installed a new air filter on the truck before the emissions test. Since the failure, I've replaced the fuel filter, cleaned the MAF, and replaced the thermostats (it was slow to warm up in May, but that may just be the way the Dmax's are).

Typically driving the truck I really don't see any smoke at all in almost all driving conditions, nor do I have any driveability problems aside from a very minor idle variation. I've tried to duplicate the emissions test (as much as I hate to see an engine run to redline unloaded), and don't see any smoke on accceleration until the truck reaches the rev limiter, and then issues a puff of very black thick smoke. I believe this puff is what is causing the test failure.

I was hoping someone might have experience with a similar problem. It appears as though CT is one of VERY few states with emissions requirements, and I have yet to find anyone with experience troubleshooting this. I will probably take it back for a restest shortly to see if mainly the change of the fuel filter has any impact on the test.

Thanks,
Rob